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Vibrio cholerae O139: An emerging pathogen
Clinical Microbiology Newsletter February 1, 1996
Vol. 18, No. 3
Vibrio cholerae O139: An Emerging Pathogen Kerstin E. Calia, M.D.
erae O 1 is a waterborne and foodborne
Fellow, Infectious Diseases Massachusetts General Hospital Boston, Massachusetts 02114
illness causing massive watery diarrhea and is capable of spreading quickly through a large population. A wellstudied toxin produced by 01 V. cholerae is chiefly responsible for this impressive secretory diarrhea. Before the discovery of serotype O139, 137 serotypes other than Ol had been identified. In general, these so-called non-O1 V. cholerae are environmental organisms, which occasionally cause human disease manifested by gastroenteritis, wound infections, and rarely, septicemia (4). They are not identified as agents of epidemic disease, which was felt to be exclusively a property of serotype O1. V. cholerae O1 is further subdivided on the basis of a number of biologic and clinical characteristics into the classical and El Tor biotypes. Within both biotypes, changes in O-antigen confer differentiation into Ogawa and Inaba serotypes. Both classical and El Tor biotypes and both Ogawa and Inaba serotypes are capable of causing cholera. Cholera has historically swept through the world in several pandemics. The sixth pandemic (since 1817) is known to have been caused by the classical biotype of V. cholerae O1 (5). The seventh and current pandemic, which began in 1961 and struck South America in 1991, is of the O1 El Tor biotype (6). Surveillance data showed that the El Tor biotype of serotype O 1 had replaced the classical biotype prior to 1992 in most endemic areas where V. cholerae was isolated from streams, lakes, ponds, and reservoirs (7).
Cholera continues, at the end of the twentieth century, to be an illness causing considerable morbidity and mortality, particularly in developing areas of the world. Until 1992, epidemic cholera had been uniquely associated with infection by Vibrio cholerae of the O1 lipopolysaccharide serotype. Since that time, one other serotype has emerged as capable of causing the widespread, florid diarrheal disease that is epidemic cholera; this serotype is the newly recognized O 139. Within the first 6 months of its emergence, this organism has been responsible for several large outbreaks of disease affecting tens of thousands of individuals and causing over a 1,000 fatalities (1-3). It has established itself over a large and ever-increasing geographic area, causing some epidemiologists to feel this is the beginning of a new cholera pandemic. The phenomenon of Vibrio cholerae O139 has also challenged some longstanding beliefs about cholera, has facilitated new understanding in the areas of epidemiology and molecular biology of cholera, and will, hopefully, in the long term enhance our understanding, identification, and management of enteric infections in general. Emergence of O139 Prior to the description of V. cholerae O139, epidemic cholera had been caused solely by V. cholerae of the O1 serotype. Cholera caused by V. cholCIvlNEEJ 18(3)17-24,1996
ELsevier
In October 1992, a cholera outbreak began in Madras, India, and over the next 2 monttis spread to neighboring cities (8). The disease was characterized by an acute secretory diarrhea indistinguishable from cholera. Vibrio cholerae was isolated from the stools of these patients, but it was not typable with O1 antisera, nor was it typable with antisera against the 137 known non-O1 V. cholerae (8). The organism produced cholera toxin as evidenced by ELISA and Southern blot hybridization, and this toxin was neutralized by antitoxin antibodies against the cholera toxin produced by O1 cholera isolates (8). This was an unusual finding because most non-O1 V. cholerae strains do not produce cholera toxin. This vibrio also lacked another toxin, a heat-stable enterotoxin produced by many non-O1 cholera vibrios but not those of the O1
In This Issue
Vibrio cholerae O139: An
Emerging Pathogen . . . . . . . . . . . . .
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An update on the new strain of vibrio that is responsiblefor epidemic cholera in various parts of the world
A Case of Bloody Diarrhea Due to Shiga-like Toxin H-Producing Escherichia coli Serotype O48:1-121 . . . . . . . . . . . . . . . . . . . . . .
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A c a s e report
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serotype. Another aspect of this organism noted at the time of the first outbreak was its antibiotic resistance pattern: it showed resistance to trimethoprim -sul famethoxazole and furazolidone and susceptibility to tetracycline. By December 1992, while the total number of cholera cases in Calcutta did not change, the percentage of isolates identified as non-O 1 cultured from these patients had risen to greater than 95%. Shortly thereafter, in January 1993, epidemic disease consistent with cholera caused by a non-O1 organism had spread to Bangladesh (1). By February of that year, I0,000 cases had been reported with 500 fatalities. Production of cholera toxin was noted by similar assays, as was the same antibiotic susceptibility pattern, including tetracycline susceptibility. The El Tor O 1 strain previously endemic to the area had been tetracycline resistant. This non-O1 strain demonstrated an unusually high attack rate in adults (despite the fact that O1 cholera was endemic in that region), reminiscent of the pattern of spread in a cholera-naive population (1). As disease associated with this organism continued to spread, intense attempts were made to further characterize the organism. The non-O1 isolate defied phage typing traditionally used to identify and differentiate O1 biotypes (2). Shimada and coworkers (9) produced antiserum against an isolate from the Madras outbreak in rabbits and demonstrated that it agglutinated other isolates from Madras and Bangladesh but not El Tor or classical O1 isolates. This serologically unique organism was designated O139 synonym Bengal, because the In'st outbreaks originated near the Bay of Bengal. As O139 continued to spread, it began to replace O1 in areas of previous O1 endemicity. By April 1993, half the
isolates in Calcutta were non-O1 (3). When surveillance culture data was retrospectively examined in India, a shift in the ratio of non-O1 to O1 isolates was seen with a seasonal increase in non-O1 isolates as far back as 1991 (10). Like Ol organisms, O139 has been isolated from surface water in geographic and temporal relation to outbreaks, but at higher rates of recovery (11). O139 continues to spread beyond India and Bangladesh, and has now been reported in a number of other countries as well, including Thailand by April 1993 and southern China by May 1993 (12,13). Other countries from which V. cholerae O139 had been isolated include Pakistan, Nepal, Burma, Malaysia, and Saudi Arabia (14). Imported cases have been diagnosed in the United Kingdom (14). Clinical cholera from strain O139 has been seen in the U.S., with the first imported case described occurring in February 1993 in a woman who had just returned from India (15). It is speculated by some that the rapid emergence of O 139 may heraid the onset of the eighth pandemic of cholera (16). E p i d e m i o l o g y of O139 I n f e c t i o n V. cholerae is an organism that causes outbreaks of disease particularly in areas of the world where plumbing and sanitation are suboptimal. V. cholerae O1 is recoverable from surface waters at a rate of less than 1% in areas of outbreaks (11). Strain O139 not only appears to share the same predisposition for waterborne spread, but one study in Bangladesh noted a higher rate of isolation of 12% from surface waters during outbreaks, suggesting perhaps that O139 has a greater ability to survive in the aquatic environment than O1 isolates (11). As previously menlioned, the replacement in the environment of the classical biotype of O 1 with
the El Tor biotype had been demonstrated after the sixth pandemic gave way to the seventh pandemic; in a similar fashion, O139 may supplant O1 isolates in the environment. The unusually high attack rate of O139 infection in adults has been reported by several researchers. During seasonal peaks of O 1 cholera in endemic Bangladesh, nearly two-thirds of cases occur in individuals under the age of 15 (17,18). Infection with one of the O1 biotypes has been held to protect an individual from recurrent cholera from that biotype later in life (19). Reports from India and Bangladesh early on in outbreaks of O139 made it clear that the proportion of adult cases was much higher than previously experienced with O1 (1,3,17). This suggested that previous infection with O1 V. cholerae, which confers lifelong immunity to that organism, does not protect against infection with V. cholerae O139. This would define a large susceptible populalion even in areas traditionally endemic for O1 cholera. Other factors that may affect the risk of an individual developing cholera include blood type and sex. For reasons that am not completely clear, those with blood type O exhibit an increased severity of disease with El Tor cholera (20). This enhanced susceptibility to cholera for individuals with blood type O has been observed for O139 as well (21). The male:female ratio of cases has been shifted from roughly equal to a slightly higher proportion of male to female patients (17). The cause and significance of this shift are unclear. Clinical Aspects o f O139 I n f e c t i o n Clinical cholera is a disease characterized by massive watery diarrhea. Fluid loss is such that hypotension from volume depletion, shock, and death can occur within a matter of hours after the onset of infection. The incubation pe-
NOTE: No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. No suggested test or procedure should be carried out unless, in the reader's judgment, its risk is justified. Because of rapid advances in medical sciences, we recommend that the independent verification of diagnoses and drug dosages should be roade. Discussions, views, and recommendations as to medical procedures, choice of drugs, and drug dosages are the responsibility of the authors.
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Clinical Microbiology Newsletter 18:3,1996
riod can range from 12 h to 3 d (22). Onset of illness frequently consists of diarrhea, vomiting (which can be severe), and is unaccompanied by high fever. Some patients with V. cholerae O1 illness complain of abdominal cramping, but patients do not have tenesmus or straining with cholera (22). Fecal matter in the stool of patients with a high volume of diarrheal fluid loss quickly clears, resulting in turbid white liquid stool classically called "rice water" stool. In addition to circulatory collapse from volume depletion, loss of electrolytes in the cholera stool play an important role in the morbidity and mortality of this disease. With large losses of bicarbonate in the stool, a severe metabolic acidosis occurs, which is exacerbated by lactic acidosis from hypopeffused tissues (22). Clinical manifestations of derangement of potassium and calcium homeostasis can include ileus, electrocardiogram changes, and muscle cramping. The minority of patients who have severe hypoglycemia (usually children) may display mental status changes or even seizures (22). In patients who are not adequately rehydrated, renal failure can result, and if rehydration fluids do not contain appropriate amounts of bicarbonate, pulmonary edema can ensue (22). Early in the first outbreaks, V. cholerae O139 was shown to cause a clinical syndrome identical to the one described above for cholera caused by O1 organisms. Three-quarters of patients presenting with O139 illness had dehydration classified as severe, and 93% in one report had vomiting (3). In their study of the epidemic in southern Bangladesh, the Cholera Working Group of the International Center for Diarrhoeal Diseases Research reported that the average adult patient required 7 liters of intravenous fluids and 11 liters of oral rehydration solution, as well as therapy with tetracycline (17). Other clinical entities caused by O139 include the report of a patient with septicemia in the setting of underlying liver disease (23). This phenomenon has been only rarely described for V. cholerae O1; it is occasionally noted with other non-O1 V. cholerae and is
Clinical Microbiology Newsl~er 18:3,1996
seen with infections from other vibrio species, especially Vibrio vulnificus (4). Currently used parenteral cholera vaccines have relatively low efficacy with protection usually lasting a matter of months (24). Laboratory evidence and data from clinical studies suggest that previous infection with O1 serotypes does not protect against O139 (15). This implies that those who have been vaccinated with the parenteral killed whole cell vaccine should not be considered protected against O 139 (15,16). Emergence of O139 has had impact on the ongoing development of improved live attenuated oral cholera vaccines. Oral challenge with serotype O1 does not provide coverage against O139, but previous infection with serotype O139 does (15,25). Evaluating vaccines that are being engineered against O139 may prove challenging, however. Development of vibriocidal antibodies is felt to be a marker of protection and is used in O1 vaccine trials to evaluate efficacy (25). Morris and colleagues demonstrated that, although infection of volunteers with O139 protected those individuals against rechallenge with the same serotype, these subjects did not produce high titers of vibriocidal antibodies (possibly consistent with the serum resistance of this encapsulated organism); thus vibriocidal antibodies may not predict protection (25). L a b o r a t o r y Diagnosis of O139 Vibrio cholerae is a motile, curved, gram-negative rod of the family Enterobacteriaceae. It is a facultative anaerobe that can ferment sucrose and mannose, and is indole positive. A number of biochemical tests are used to differentiate classical from El Tor O 1 biotypes, and these have been applied to O139 as well. Like serotype O1 El Tor organisms, serotype O139 is VogesProskauer positive and resistant to polymyxin B (15). O139 is also resistant to the vibriostatic compound 0/129 (2Adiamino-6,7-diisopropyl pteridine) (1). Similar to the El Tor biotype ofO1 V. cholerae, O139 produces a zone of hemolysis when grown on sheep blood agar. V. cholerae O139 is encapsulated, a trait the O 1 serotype does not share but that some non-O1, non-O139 sero-
types do (27). Stool specimens from patients suspected of having cholera should be cultured on thiosulfate citrate bile salts sucrose (TCBS) medium, the preferred medium for identification and culture of V. cholerae, to isolate strain O139. V. cholerae O139 is typical of cholera vibrios in that it forms golden-yellow colonies on TCBS medium due to the fermentation of sucrose. Vibrio species other than V. cholerae tend to produce dark green colonies on this sprucegreen colored agar. Another medium occasionally used for enrichment and identification of V. cholerae is taurocholite-tellurite-gelatin agar (T'rGA). When grown on this medium, O139 produces gray colonies with large dark centers and a turbid zone around the colony due to production of gelatinase (15). On both Iq'GA and a nonselective medium, Luria Bertani agar, both opaque and translucent colony types can sometimes be seen. This is probably due to the encapsulation of O139, contrasted with the unencapsulated O1, and is comparable to the occasional encapsulation of non-O1 V. cholerae and other encapsulated vibrios such as Vibrio vulnificus (15,27). Like other V. cholerae strains and unlike the halophilic marine vibrio species, O139 is also capable of growing in liquid medium with low salt concentration (15). If rectal swabs instead of stool are cultured, then a transport medium such as Cary-Blair should be used. The laboratory should be notified that V. cholerae is suspected so that the cultures may be planted onto appropriate media. If contacts or history suggest it, it should be noted that V. cholerae O139 might be the infectious agent. An isolate of V. cholerae that does not agglutinate with Ol antiserum should be sent to the state public health laboratory if the clinical syndrome is compatible with severe cholera, if the individual has travelled to an area of the world where O139 is found, or if the case has been associated with an outbreak (14). Several slide agglutination assays have been developed for V. cholerae O1, some for direct use on stool and/or in the field, and similar assays are being developed for O139 (28). At
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least one stool coagglutination assay is already commercially available (New Horizons Diagnostics Corporation, Columbia, MD).
Molecular Biology of O139 Vibrio cholerae possesses several essential virulence factors, of which the most important is cholera toxin. Cholera toxin comprises an A-subunit, which is the enzymatic,ally active portion of the toxin, and a pentamer of Bsubunits, which serve to bind the holotoxin to the intestinal epithelial cell. The A-subunit activates adenylate cyclase and increases intracellular cyclic AMP, resulting in secretion of chloride, bicarbonate, and water into the gut lumen. This toxin is felt to be the primary cause of the clinical manifestations of massive diarrhea and severe electrolyte abnormalities. In O 1 organisms, the cholera toxin (CTX) genes exist in a virulence cassette that is now recognized as a transposable element. The core region contains the genes for the A- and B-subunits of the toxin and for several other virulence factors later discovered. These include zot, or zonula occludens toxin; ace, accessory cholera enterotoxin; and cep, whose gene product is a pilin-like intestinal colonization factor (29). The core region is flanked by two or more copies of a repetitive sequence RS1, which is thought to be a site-specific recombinase with an 18 base pair chromosomal target sequence termed att RS1. An additional important virulence factor (encoded elsewhere on the chromosome) is the toxin coregulated pilus, or TCP. Both TCP and CTX are regulated by a gene called toxR (30). Multiple investigators set out to look for these genes previously characterized in O1 organisms to gain insight into the virulence of O 139, Most of the 137 nonO1 serotypes previously known carry the cholera toxin virulence cassette less than 25% of the time (with variation in the incidence of this gene with the geographic origin of the isolate) and do not carry TCP (31,32). Non-O1 isolates that do produce cholera toxin are unusual and do not cause epidemic spread of disease. When examined by Southeru blot analysis, not only did O139 isolates possess the virulence cassette, but they tended to have multiple copies of
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the core region, leading to speculation that possession of two or more copies of the toxin genetic element may enhance virulence of this organism (32). The regulatory gene toxR was uniformly present in O139 isolates, as were genes in the tcp operon (33). In the laboratory, conditions required to induce ToxR and thus TCP and toxin production differ between classical and El Tor biotypes. In this respect, O139 behaves like an El Tor in that optimal conditions required to induce production of cholera toxin in vivo are the same as those for El Tor O 1 isolates and not classical O1 isolates (33). Other virulence factors of V. cholerae have been found in the O139 serotype. These include iron-regulated genes important in virulence such as fur, h'gA, and viuA, which by Southern blot hybridization are indistinguishable between O1 El Tor and O139 isolates (34). Data reveal that O139 has an abbreviated O-antigen and is encapsulated. The polysaccharide makeup of the capsule includes colitose, an unusual saccharide in V. cholerae (35). Encapsulation ofO139, as in non-O1 V. cholerae, may play a role in allowing the organism to resist serum killing and in its invasiveness (because, like some non-O1 isolates but not the O1 serotype, O 139 is lethal when intradermally injected into mice) (15). When the genes for the O-antigen synthetic apparatus, the r.tb gene cluster, were examined, it was found that a large amount of genetic material was missing (36). This was not in the form of a simple deletion, however, because some genes within the center of the rfb gene complex were still present. Recent data suggest that both the lipopolysaccharide (LPS) and the capsule together may comprise the O 139 antigen, and not just the LPS (37,38). Synthesis of these two moieties may be linked. Given the many similarities between V. cholerae O 1 El Tor biotype and V. cholerae O139, it is not surprising that many investigators surmise that O 139 arose from an O1 El Tor strain, as opposed to an alternative hypothesis that its ancestor may have been a non-O1 organism that acquired the toxin and separately acquired the genes for Tcp and
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lost those for the non-O1 enterotoxin (15). Some complex recombinational event(s) may have taken place to give rise to this organism. T h e r a p y o f O139 I n f e c t i o n s The mainstay of therapy for cholera first and foremost is rehydration. This imperative should be followed for O139- as well as Ol-induced cholera, given that the mechanisms of disease and the clinical syndromes are essentially the same. Like O1 V. cholerae, V. cholerae O139 appears to be a transient inhabitant of the human host, with infection and carriage lasting a matter of days (39). Vigorous oral rehydration should be pursued; for those unable to take sufficient fluids PO, IV rehydration is required. Antibiotic use should be viewed as an important adjunct to rehydration therapy. It is worth reviewing guidelines for rehydration; a recent study (40) revealed health-care providers and pharmacies in the U.S. may be inadequately hydrating patients, may look to antibiotic therapy rather than volume replacement as the mainstay of therapy with potentially deleterious results, and may be using inappropriate solutions for rehydration. Rehydration therapy is one of the simplest treatments available. It is replacement of volume already lost and then continuing replacement of ongoing losses that save lives in treatment of cholera. Both oral and intravenous rehydration solutions are formulated to provide appropriately balanced electrolyte solutions given the composition of fluid losses in cholera. This is crucial because giving water alone or inappropriately balanced electrolyte solutions can result in further severe metabolic derangements (e.g., hyponatremia, hypokalemia). All patients who can take PO fluids should receive oral rehydration solution except (i) those with severe (>10% of body weight) dehydration, (ii) those with stool volume rates >10 ml/kg/h, and (iii) those with continued vomiting (22). Vigilant measurement and recording of fluid losses as well as intake are essential to provide adequate replacement of ongoing losses. The optimal IV rehydration solution available in the U.S. is lactated
Clinical Microbiology Newsletter 18:3,1996
Ringer's solution (I.R) (41). LR conrains the correct amount of sodium, bicarbonate, and chloride given the electrolyte losses in cholera stool, but its concenlration of potassium is lower than that of both cholera stool and IV rehydration solutions used elsewhere in the world (e.g., Dhaka solution) (22). For this reason, serum potassium should be monitored and supplemented as needed. If patients suffer hypoglycemia, LR with 5% dexlrose can be used (22). PO fluids should be started when a patient is capable of taking them. There are a number of ready-made oral rehydration salts (ORS) solutions available in countries where diarrheal diseases are endemic. In the U.S., WHO Oral Rehydration Salts Solution (available through Jianas Brothers) and Rehydralyte (Ross Laboratories, Columbus, OH) are used. It is important to note that the sodium contents of these solutions are lower than some of the internationally used solutions, but otherwise these two formulations contain the optimal concentration of electrolytes and glucose to replace cholera losses (41). Patients can be successfully rehydrated within the fast few hours of presentation. Those whose stool volume is documented to be decreasing and who can demonstrate the ability to drink enough fluid to keep up with stool losses can be sent home. For severely dehydrated individuals, this usually takes 1 to 3 d (22). Patients usually do not relapse but should be advised to return for medical attention if they do. Antibiotic therapy in addition to hydration is useful as it shortens both the duration of diarrhea and length of excretion of the organism (22). V. cholerae O139, as previously noted, is resistant to trimethoprim-sulfamethoxazole and furazolidone. Antibiotic options therefore include (dosages for adults): (i) tetracycline, 500 mg p.o. QID for 3 d; (ii) doxycycline, 300 mg p.o. as a one-time dose; (iii) erythromycin, 250 mg p.o. QID for 3 d; or (iv) norfloxacin, 400 mg p.o. BID for 3 d.
those travelling to areas of the world endemic for cholera (including O1 and/or O139 serotypes) more information is available through the CDC's traveller's hotline: (404) 332-4559 (English) or (404) 330-3132 (Spanish).
Reporting of Cases Cases of confirmed or suspected cholera, whether O1 or O139, should be reported to the local board of health and state division of epidemiology. For
6.
Clinical Microbiology Newsletter 18:3,1996
erae O1 strains isolated between 1961
8.
Conclusion V. cholerae O139 is an example of a novel organism quickly establishing itself as a pathogen of major epidemic impact. It is a serologically unique organism capable of causing epidemic cholera, which was previously the realm of the O1 serotype alone. O139 has established itself in areas endemic for cholera and caused considerable morbidity and mortality. This organism has a propensity to atlack those immunologically naive to its serotype, which has important implications in epidemiology and vaccine development of cholera. Clinical presentation and Ireatment of disease of the O 1 and O 139 serotypes of V. cholerae are essentially identical. Investigating the genetic armamentarium of O139 is giving us valuable insight into the molecular pathogenesis of both serotypes and of V. cholerae in general. Ideally, this will help us in devising further strategies to protect ourselves from cholera and related diseases. References
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22, Bennish, M.L. 1994. Cholera: pathophysiology, clinical features, and treatment, p. 229-255. In I.K. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 23. Jesudason, M.V., A.M. Cherian, and T.J. John. 1993. Bloodstream invasion by Vibrio cholerae O139. Lancet 342:431. 24. Saroso, J.S., et al. 1978. A controlled field trial of plain and aluminum hydroxide-adsorbed cholera vaccines in Surabaya, Indonesia, during 19731975. Bull. World Health Organ. 56:619--627. 25. Morris, J.G., et al. 1993, Challenge and rechallenge studies with Vibrio cholerae O139 in North American volunteers. Abstracts of the 33rd Annual Meeting of the Infectious Disease Society of America, Abstract no. 231. 26. Levine, M.M., and C.O. Tackett. 1994. Recombinant live cholera vaccines, p. 395--413. In I.K. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 27. Johnson, J.A., et al, 1994. Vibrio cholerae O139 synonym Bengal is closely related to Vibrio cholerae E1 Tor but has important differences. Infect. hnmun. 62:2108-2110. 28. Hasan, J.A.K., et al. 1993. Development of rapid immunodiagnostics kits to detect Vibrio cholerae O 139 syno-
nym Bengal, p. 222. Abstracts of the 29th Joint Conference on Cholera and Related Diarrheal Diseases, The United States-Japan Cooperative Medical Science Program. 29. Kaper, J.B., A. Fasano, and M. Trucksis. 1994. Toxins of Vibrio cholerae, p. 145-176. In LK. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 30. DiRita, V.J., et al. 1991. Regulatory cascade controls virulence in Vibrio cholerae. Proc. Natl. Acad. Sci. USA. 88:5403--5407. 31. Morris, J.G. 1990, Non-O group 1 Vibrio cholerae: a look at the epidemiology of an occasional pathogen. Epidemiol. Rev. 12:179-191. 32. Waidor, M.K., and J.J. Mekalanos. 1994. Emergence of a new cholera pandemic: molecular analysis of virulence determinants in Vibrio cholerae O139 and development of a live vaccine prototype. J. Infect. Dis. 170:278-283. 33. Waidor, M.K., and J.J. Mekalanos. 1994. ToxR regulates virulence gene expression in non-O1 strains of Vibrio cholerae that cause epidemic cholera. Infect. Immun. 62:72-78. 34. Calia, K.E., et al. 1994. Comparison of Vibrio cholerae O 139 with Vibrio cholerae O1 classical and El Tor biotypes. Infect. hmnun. 62:1504-1506. 35. Weintraub, A., et al. 1994. Vibrio cholerae O139 Bengal possesses a capsular
polysaccharide which may confer increased virulence. Microb. Pathog. 16:235-241. 36. Manning, P.A., U.H. Stroeher, and R. Morona. 1994. Molecular basis for O-antigen biosynthesis in Vibrio cholerae O1: Ogawa-Inaba switching, p. 77-94. In I.K. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 37. Waidor, M.K., R.R. Colwell, and J.J. Mekalanos. 1994. The Vibrio cholerae O139 serogroup antigen includes an Oantigen capsule and lipopolysaccharide virulence determinants. Proc. Natl. Acad. Sci. USA. 91:11388-11392. 38, Comstock, L.E., et al. 1995. The capsule and the O-antigen of Vibrio cholerae O139 Bengal are associated with a genetic region not present in Vibrio cholerae O1. Infect. Immun. 63:317323. 39. Faruque, A.S.G., et al. 1994. Studies of infection with Vibrio cholerae O 139 synonym Bengal in family contacts of index cases. Trans. R. Soc. Trop. Med. Hyg. 88:439. 40. Besser, R.E., et al. 1994. Diagnosis and treatment of cholera in the United States: are we prepared? JAMA. 272:1203-1209. 41. Swerdlow, D.S., and A.A. Ries. 1992. Cholera in the Americas: guidelines for the clinician. JAMA. 267:1495-1499.
Case Report
A Case of Bloody Diarrhea Due to Shiga-like Toxin II-Producing Escherichia coli Serotype O48:H21 Sharon L. Abbott, B.A. Microbial Diseases Laboratory Division of Communicable Disease Control California Department of Health Services Berkeley, California 94704-1011 Evangeline G. Sowers, B.S. Centers for Disease Control and Prevention Atlanta, Georgia 30333 Stojanka Aleksic, Ph.D. National Reference Center for Enteric Pathogens Institute of Hygiene Hamburg, Germany
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J. Michael Janda, Ph.D. Microbial Diseases Laboratory Division of Communicable Disease Control Berkeley, California 94704-1 O11 Enteroinvasive (EIEC) and enterohemorrhagic (EHEC) Escherichia coil are the two major groups of diarrheagenic E. coli associated with bloody diarrhea (1). Although E1EC infections are normally limited to persons returning from foreign travel, particularly from Mexico, EHEC is an emerging infectious agent in the U.S, (2). The © 1996 Elsevier Science Inc.
single most c o m m o n EHEC serotype associated with bloody diarrhea is E. coli O157:H7, responsible for >37 to 39% o f all recognized cases o f hemorrhagic colitis (3). Although the disease is benign in its early phases (secretory illness), it rapidly progresses to a more fuhninant form (colitis), which in pediatric patients may be life-threatening as a result o f the possible development o f secondary sequelae such as hemolytic uremic syndrome. Although O157:H7 is the only seroClinical Microbiology Newstetter [8:3,19q(~
Vol. 18, No. 3
Vibrio cholerae O139: An Emerging Pathogen Kerstin E. Calia, M.D.
erae O 1 is a waterborne and foodborne
Fellow, Infectious Diseases Massachusetts General Hospital Boston, Massachusetts 02114
illness causing massive watery diarrhea and is capable of spreading quickly through a large population. A wellstudied toxin produced by 01 V. cholerae is chiefly responsible for this impressive secretory diarrhea. Before the discovery of serotype O139, 137 serotypes other than Ol had been identified. In general, these so-called non-O1 V. cholerae are environmental organisms, which occasionally cause human disease manifested by gastroenteritis, wound infections, and rarely, septicemia (4). They are not identified as agents of epidemic disease, which was felt to be exclusively a property of serotype O1. V. cholerae O1 is further subdivided on the basis of a number of biologic and clinical characteristics into the classical and El Tor biotypes. Within both biotypes, changes in O-antigen confer differentiation into Ogawa and Inaba serotypes. Both classical and El Tor biotypes and both Ogawa and Inaba serotypes are capable of causing cholera. Cholera has historically swept through the world in several pandemics. The sixth pandemic (since 1817) is known to have been caused by the classical biotype of V. cholerae O1 (5). The seventh and current pandemic, which began in 1961 and struck South America in 1991, is of the O1 El Tor biotype (6). Surveillance data showed that the El Tor biotype of serotype O 1 had replaced the classical biotype prior to 1992 in most endemic areas where V. cholerae was isolated from streams, lakes, ponds, and reservoirs (7).
Cholera continues, at the end of the twentieth century, to be an illness causing considerable morbidity and mortality, particularly in developing areas of the world. Until 1992, epidemic cholera had been uniquely associated with infection by Vibrio cholerae of the O1 lipopolysaccharide serotype. Since that time, one other serotype has emerged as capable of causing the widespread, florid diarrheal disease that is epidemic cholera; this serotype is the newly recognized O 139. Within the first 6 months of its emergence, this organism has been responsible for several large outbreaks of disease affecting tens of thousands of individuals and causing over a 1,000 fatalities (1-3). It has established itself over a large and ever-increasing geographic area, causing some epidemiologists to feel this is the beginning of a new cholera pandemic. The phenomenon of Vibrio cholerae O139 has also challenged some longstanding beliefs about cholera, has facilitated new understanding in the areas of epidemiology and molecular biology of cholera, and will, hopefully, in the long term enhance our understanding, identification, and management of enteric infections in general. Emergence of O139 Prior to the description of V. cholerae O139, epidemic cholera had been caused solely by V. cholerae of the O1 serotype. Cholera caused by V. cholCIvlNEEJ 18(3)17-24,1996
ELsevier
In October 1992, a cholera outbreak began in Madras, India, and over the next 2 monttis spread to neighboring cities (8). The disease was characterized by an acute secretory diarrhea indistinguishable from cholera. Vibrio cholerae was isolated from the stools of these patients, but it was not typable with O1 antisera, nor was it typable with antisera against the 137 known non-O1 V. cholerae (8). The organism produced cholera toxin as evidenced by ELISA and Southern blot hybridization, and this toxin was neutralized by antitoxin antibodies against the cholera toxin produced by O1 cholera isolates (8). This was an unusual finding because most non-O1 V. cholerae strains do not produce cholera toxin. This vibrio also lacked another toxin, a heat-stable enterotoxin produced by many non-O1 cholera vibrios but not those of the O1
In This Issue
Vibrio cholerae O139: An
Emerging Pathogen . . . . . . . . . . . . .
17
An update on the new strain of vibrio that is responsiblefor epidemic cholera in various parts of the world
A Case of Bloody Diarrhea Due to Shiga-like Toxin H-Producing Escherichia coli Serotype O48:1-121 . . . . . . . . . . . . . . . . . . . . . .
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A c a s e report
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serotype. Another aspect of this organism noted at the time of the first outbreak was its antibiotic resistance pattern: it showed resistance to trimethoprim -sul famethoxazole and furazolidone and susceptibility to tetracycline. By December 1992, while the total number of cholera cases in Calcutta did not change, the percentage of isolates identified as non-O 1 cultured from these patients had risen to greater than 95%. Shortly thereafter, in January 1993, epidemic disease consistent with cholera caused by a non-O1 organism had spread to Bangladesh (1). By February of that year, I0,000 cases had been reported with 500 fatalities. Production of cholera toxin was noted by similar assays, as was the same antibiotic susceptibility pattern, including tetracycline susceptibility. The El Tor O 1 strain previously endemic to the area had been tetracycline resistant. This non-O1 strain demonstrated an unusually high attack rate in adults (despite the fact that O1 cholera was endemic in that region), reminiscent of the pattern of spread in a cholera-naive population (1). As disease associated with this organism continued to spread, intense attempts were made to further characterize the organism. The non-O1 isolate defied phage typing traditionally used to identify and differentiate O1 biotypes (2). Shimada and coworkers (9) produced antiserum against an isolate from the Madras outbreak in rabbits and demonstrated that it agglutinated other isolates from Madras and Bangladesh but not El Tor or classical O1 isolates. This serologically unique organism was designated O139 synonym Bengal, because the In'st outbreaks originated near the Bay of Bengal. As O139 continued to spread, it began to replace O1 in areas of previous O1 endemicity. By April 1993, half the
isolates in Calcutta were non-O1 (3). When surveillance culture data was retrospectively examined in India, a shift in the ratio of non-O1 to O1 isolates was seen with a seasonal increase in non-O1 isolates as far back as 1991 (10). Like Ol organisms, O139 has been isolated from surface water in geographic and temporal relation to outbreaks, but at higher rates of recovery (11). O139 continues to spread beyond India and Bangladesh, and has now been reported in a number of other countries as well, including Thailand by April 1993 and southern China by May 1993 (12,13). Other countries from which V. cholerae O139 had been isolated include Pakistan, Nepal, Burma, Malaysia, and Saudi Arabia (14). Imported cases have been diagnosed in the United Kingdom (14). Clinical cholera from strain O139 has been seen in the U.S., with the first imported case described occurring in February 1993 in a woman who had just returned from India (15). It is speculated by some that the rapid emergence of O 139 may heraid the onset of the eighth pandemic of cholera (16). E p i d e m i o l o g y of O139 I n f e c t i o n V. cholerae is an organism that causes outbreaks of disease particularly in areas of the world where plumbing and sanitation are suboptimal. V. cholerae O1 is recoverable from surface waters at a rate of less than 1% in areas of outbreaks (11). Strain O139 not only appears to share the same predisposition for waterborne spread, but one study in Bangladesh noted a higher rate of isolation of 12% from surface waters during outbreaks, suggesting perhaps that O139 has a greater ability to survive in the aquatic environment than O1 isolates (11). As previously menlioned, the replacement in the environment of the classical biotype of O 1 with
the El Tor biotype had been demonstrated after the sixth pandemic gave way to the seventh pandemic; in a similar fashion, O139 may supplant O1 isolates in the environment. The unusually high attack rate of O139 infection in adults has been reported by several researchers. During seasonal peaks of O 1 cholera in endemic Bangladesh, nearly two-thirds of cases occur in individuals under the age of 15 (17,18). Infection with one of the O1 biotypes has been held to protect an individual from recurrent cholera from that biotype later in life (19). Reports from India and Bangladesh early on in outbreaks of O139 made it clear that the proportion of adult cases was much higher than previously experienced with O1 (1,3,17). This suggested that previous infection with O1 V. cholerae, which confers lifelong immunity to that organism, does not protect against infection with V. cholerae O139. This would define a large susceptible populalion even in areas traditionally endemic for O1 cholera. Other factors that may affect the risk of an individual developing cholera include blood type and sex. For reasons that am not completely clear, those with blood type O exhibit an increased severity of disease with El Tor cholera (20). This enhanced susceptibility to cholera for individuals with blood type O has been observed for O139 as well (21). The male:female ratio of cases has been shifted from roughly equal to a slightly higher proportion of male to female patients (17). The cause and significance of this shift are unclear. Clinical Aspects o f O139 I n f e c t i o n Clinical cholera is a disease characterized by massive watery diarrhea. Fluid loss is such that hypotension from volume depletion, shock, and death can occur within a matter of hours after the onset of infection. The incubation pe-
NOTE: No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. No suggested test or procedure should be carried out unless, in the reader's judgment, its risk is justified. Because of rapid advances in medical sciences, we recommend that the independent verification of diagnoses and drug dosages should be roade. Discussions, views, and recommendations as to medical procedures, choice of drugs, and drug dosages are the responsibility of the authors.
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Clinical Microbiology Newsletter 18:3,1996
riod can range from 12 h to 3 d (22). Onset of illness frequently consists of diarrhea, vomiting (which can be severe), and is unaccompanied by high fever. Some patients with V. cholerae O1 illness complain of abdominal cramping, but patients do not have tenesmus or straining with cholera (22). Fecal matter in the stool of patients with a high volume of diarrheal fluid loss quickly clears, resulting in turbid white liquid stool classically called "rice water" stool. In addition to circulatory collapse from volume depletion, loss of electrolytes in the cholera stool play an important role in the morbidity and mortality of this disease. With large losses of bicarbonate in the stool, a severe metabolic acidosis occurs, which is exacerbated by lactic acidosis from hypopeffused tissues (22). Clinical manifestations of derangement of potassium and calcium homeostasis can include ileus, electrocardiogram changes, and muscle cramping. The minority of patients who have severe hypoglycemia (usually children) may display mental status changes or even seizures (22). In patients who are not adequately rehydrated, renal failure can result, and if rehydration fluids do not contain appropriate amounts of bicarbonate, pulmonary edema can ensue (22). Early in the first outbreaks, V. cholerae O139 was shown to cause a clinical syndrome identical to the one described above for cholera caused by O1 organisms. Three-quarters of patients presenting with O139 illness had dehydration classified as severe, and 93% in one report had vomiting (3). In their study of the epidemic in southern Bangladesh, the Cholera Working Group of the International Center for Diarrhoeal Diseases Research reported that the average adult patient required 7 liters of intravenous fluids and 11 liters of oral rehydration solution, as well as therapy with tetracycline (17). Other clinical entities caused by O139 include the report of a patient with septicemia in the setting of underlying liver disease (23). This phenomenon has been only rarely described for V. cholerae O1; it is occasionally noted with other non-O1 V. cholerae and is
Clinical Microbiology Newsl~er 18:3,1996
seen with infections from other vibrio species, especially Vibrio vulnificus (4). Currently used parenteral cholera vaccines have relatively low efficacy with protection usually lasting a matter of months (24). Laboratory evidence and data from clinical studies suggest that previous infection with O1 serotypes does not protect against O139 (15). This implies that those who have been vaccinated with the parenteral killed whole cell vaccine should not be considered protected against O 139 (15,16). Emergence of O139 has had impact on the ongoing development of improved live attenuated oral cholera vaccines. Oral challenge with serotype O1 does not provide coverage against O139, but previous infection with serotype O139 does (15,25). Evaluating vaccines that are being engineered against O139 may prove challenging, however. Development of vibriocidal antibodies is felt to be a marker of protection and is used in O1 vaccine trials to evaluate efficacy (25). Morris and colleagues demonstrated that, although infection of volunteers with O139 protected those individuals against rechallenge with the same serotype, these subjects did not produce high titers of vibriocidal antibodies (possibly consistent with the serum resistance of this encapsulated organism); thus vibriocidal antibodies may not predict protection (25). L a b o r a t o r y Diagnosis of O139 Vibrio cholerae is a motile, curved, gram-negative rod of the family Enterobacteriaceae. It is a facultative anaerobe that can ferment sucrose and mannose, and is indole positive. A number of biochemical tests are used to differentiate classical from El Tor O 1 biotypes, and these have been applied to O139 as well. Like serotype O1 El Tor organisms, serotype O139 is VogesProskauer positive and resistant to polymyxin B (15). O139 is also resistant to the vibriostatic compound 0/129 (2Adiamino-6,7-diisopropyl pteridine) (1). Similar to the El Tor biotype ofO1 V. cholerae, O139 produces a zone of hemolysis when grown on sheep blood agar. V. cholerae O139 is encapsulated, a trait the O 1 serotype does not share but that some non-O1, non-O139 sero-
types do (27). Stool specimens from patients suspected of having cholera should be cultured on thiosulfate citrate bile salts sucrose (TCBS) medium, the preferred medium for identification and culture of V. cholerae, to isolate strain O139. V. cholerae O139 is typical of cholera vibrios in that it forms golden-yellow colonies on TCBS medium due to the fermentation of sucrose. Vibrio species other than V. cholerae tend to produce dark green colonies on this sprucegreen colored agar. Another medium occasionally used for enrichment and identification of V. cholerae is taurocholite-tellurite-gelatin agar (T'rGA). When grown on this medium, O139 produces gray colonies with large dark centers and a turbid zone around the colony due to production of gelatinase (15). On both Iq'GA and a nonselective medium, Luria Bertani agar, both opaque and translucent colony types can sometimes be seen. This is probably due to the encapsulation of O139, contrasted with the unencapsulated O1, and is comparable to the occasional encapsulation of non-O1 V. cholerae and other encapsulated vibrios such as Vibrio vulnificus (15,27). Like other V. cholerae strains and unlike the halophilic marine vibrio species, O139 is also capable of growing in liquid medium with low salt concentration (15). If rectal swabs instead of stool are cultured, then a transport medium such as Cary-Blair should be used. The laboratory should be notified that V. cholerae is suspected so that the cultures may be planted onto appropriate media. If contacts or history suggest it, it should be noted that V. cholerae O139 might be the infectious agent. An isolate of V. cholerae that does not agglutinate with Ol antiserum should be sent to the state public health laboratory if the clinical syndrome is compatible with severe cholera, if the individual has travelled to an area of the world where O139 is found, or if the case has been associated with an outbreak (14). Several slide agglutination assays have been developed for V. cholerae O1, some for direct use on stool and/or in the field, and similar assays are being developed for O139 (28). At
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least one stool coagglutination assay is already commercially available (New Horizons Diagnostics Corporation, Columbia, MD).
Molecular Biology of O139 Vibrio cholerae possesses several essential virulence factors, of which the most important is cholera toxin. Cholera toxin comprises an A-subunit, which is the enzymatic,ally active portion of the toxin, and a pentamer of Bsubunits, which serve to bind the holotoxin to the intestinal epithelial cell. The A-subunit activates adenylate cyclase and increases intracellular cyclic AMP, resulting in secretion of chloride, bicarbonate, and water into the gut lumen. This toxin is felt to be the primary cause of the clinical manifestations of massive diarrhea and severe electrolyte abnormalities. In O 1 organisms, the cholera toxin (CTX) genes exist in a virulence cassette that is now recognized as a transposable element. The core region contains the genes for the A- and B-subunits of the toxin and for several other virulence factors later discovered. These include zot, or zonula occludens toxin; ace, accessory cholera enterotoxin; and cep, whose gene product is a pilin-like intestinal colonization factor (29). The core region is flanked by two or more copies of a repetitive sequence RS1, which is thought to be a site-specific recombinase with an 18 base pair chromosomal target sequence termed att RS1. An additional important virulence factor (encoded elsewhere on the chromosome) is the toxin coregulated pilus, or TCP. Both TCP and CTX are regulated by a gene called toxR (30). Multiple investigators set out to look for these genes previously characterized in O1 organisms to gain insight into the virulence of O 139, Most of the 137 nonO1 serotypes previously known carry the cholera toxin virulence cassette less than 25% of the time (with variation in the incidence of this gene with the geographic origin of the isolate) and do not carry TCP (31,32). Non-O1 isolates that do produce cholera toxin are unusual and do not cause epidemic spread of disease. When examined by Southeru blot analysis, not only did O139 isolates possess the virulence cassette, but they tended to have multiple copies of
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the core region, leading to speculation that possession of two or more copies of the toxin genetic element may enhance virulence of this organism (32). The regulatory gene toxR was uniformly present in O139 isolates, as were genes in the tcp operon (33). In the laboratory, conditions required to induce ToxR and thus TCP and toxin production differ between classical and El Tor biotypes. In this respect, O139 behaves like an El Tor in that optimal conditions required to induce production of cholera toxin in vivo are the same as those for El Tor O 1 isolates and not classical O1 isolates (33). Other virulence factors of V. cholerae have been found in the O139 serotype. These include iron-regulated genes important in virulence such as fur, h'gA, and viuA, which by Southern blot hybridization are indistinguishable between O1 El Tor and O139 isolates (34). Data reveal that O139 has an abbreviated O-antigen and is encapsulated. The polysaccharide makeup of the capsule includes colitose, an unusual saccharide in V. cholerae (35). Encapsulation ofO139, as in non-O1 V. cholerae, may play a role in allowing the organism to resist serum killing and in its invasiveness (because, like some non-O1 isolates but not the O1 serotype, O 139 is lethal when intradermally injected into mice) (15). When the genes for the O-antigen synthetic apparatus, the r.tb gene cluster, were examined, it was found that a large amount of genetic material was missing (36). This was not in the form of a simple deletion, however, because some genes within the center of the rfb gene complex were still present. Recent data suggest that both the lipopolysaccharide (LPS) and the capsule together may comprise the O 139 antigen, and not just the LPS (37,38). Synthesis of these two moieties may be linked. Given the many similarities between V. cholerae O 1 El Tor biotype and V. cholerae O139, it is not surprising that many investigators surmise that O 139 arose from an O1 El Tor strain, as opposed to an alternative hypothesis that its ancestor may have been a non-O1 organism that acquired the toxin and separately acquired the genes for Tcp and
© 1996 Elsevier Science Inc.
lost those for the non-O1 enterotoxin (15). Some complex recombinational event(s) may have taken place to give rise to this organism. T h e r a p y o f O139 I n f e c t i o n s The mainstay of therapy for cholera first and foremost is rehydration. This imperative should be followed for O139- as well as Ol-induced cholera, given that the mechanisms of disease and the clinical syndromes are essentially the same. Like O1 V. cholerae, V. cholerae O139 appears to be a transient inhabitant of the human host, with infection and carriage lasting a matter of days (39). Vigorous oral rehydration should be pursued; for those unable to take sufficient fluids PO, IV rehydration is required. Antibiotic use should be viewed as an important adjunct to rehydration therapy. It is worth reviewing guidelines for rehydration; a recent study (40) revealed health-care providers and pharmacies in the U.S. may be inadequately hydrating patients, may look to antibiotic therapy rather than volume replacement as the mainstay of therapy with potentially deleterious results, and may be using inappropriate solutions for rehydration. Rehydration therapy is one of the simplest treatments available. It is replacement of volume already lost and then continuing replacement of ongoing losses that save lives in treatment of cholera. Both oral and intravenous rehydration solutions are formulated to provide appropriately balanced electrolyte solutions given the composition of fluid losses in cholera. This is crucial because giving water alone or inappropriately balanced electrolyte solutions can result in further severe metabolic derangements (e.g., hyponatremia, hypokalemia). All patients who can take PO fluids should receive oral rehydration solution except (i) those with severe (>10% of body weight) dehydration, (ii) those with stool volume rates >10 ml/kg/h, and (iii) those with continued vomiting (22). Vigilant measurement and recording of fluid losses as well as intake are essential to provide adequate replacement of ongoing losses. The optimal IV rehydration solution available in the U.S. is lactated
Clinical Microbiology Newsletter 18:3,1996
Ringer's solution (I.R) (41). LR conrains the correct amount of sodium, bicarbonate, and chloride given the electrolyte losses in cholera stool, but its concenlration of potassium is lower than that of both cholera stool and IV rehydration solutions used elsewhere in the world (e.g., Dhaka solution) (22). For this reason, serum potassium should be monitored and supplemented as needed. If patients suffer hypoglycemia, LR with 5% dexlrose can be used (22). PO fluids should be started when a patient is capable of taking them. There are a number of ready-made oral rehydration salts (ORS) solutions available in countries where diarrheal diseases are endemic. In the U.S., WHO Oral Rehydration Salts Solution (available through Jianas Brothers) and Rehydralyte (Ross Laboratories, Columbus, OH) are used. It is important to note that the sodium contents of these solutions are lower than some of the internationally used solutions, but otherwise these two formulations contain the optimal concentration of electrolytes and glucose to replace cholera losses (41). Patients can be successfully rehydrated within the fast few hours of presentation. Those whose stool volume is documented to be decreasing and who can demonstrate the ability to drink enough fluid to keep up with stool losses can be sent home. For severely dehydrated individuals, this usually takes 1 to 3 d (22). Patients usually do not relapse but should be advised to return for medical attention if they do. Antibiotic therapy in addition to hydration is useful as it shortens both the duration of diarrhea and length of excretion of the organism (22). V. cholerae O139, as previously noted, is resistant to trimethoprim-sulfamethoxazole and furazolidone. Antibiotic options therefore include (dosages for adults): (i) tetracycline, 500 mg p.o. QID for 3 d; (ii) doxycycline, 300 mg p.o. as a one-time dose; (iii) erythromycin, 250 mg p.o. QID for 3 d; or (iv) norfloxacin, 400 mg p.o. BID for 3 d.
those travelling to areas of the world endemic for cholera (including O1 and/or O139 serotypes) more information is available through the CDC's traveller's hotline: (404) 332-4559 (English) or (404) 330-3132 (Spanish).
Reporting of Cases Cases of confirmed or suspected cholera, whether O1 or O139, should be reported to the local board of health and state division of epidemiology. For
6.
Clinical Microbiology Newsletter 18:3,1996
erae O1 strains isolated between 1961
8.
Conclusion V. cholerae O139 is an example of a novel organism quickly establishing itself as a pathogen of major epidemic impact. It is a serologically unique organism capable of causing epidemic cholera, which was previously the realm of the O1 serotype alone. O139 has established itself in areas endemic for cholera and caused considerable morbidity and mortality. This organism has a propensity to atlack those immunologically naive to its serotype, which has important implications in epidemiology and vaccine development of cholera. Clinical presentation and Ireatment of disease of the O 1 and O 139 serotypes of V. cholerae are essentially identical. Investigating the genetic armamentarium of O139 is giving us valuable insight into the molecular pathogenesis of both serotypes and of V. cholerae in general. Ideally, this will help us in devising further strategies to protect ourselves from cholera and related diseases. References
1.
Albert, M.J., et al. 1993. Large outbreak of clinical cholera due to Vibrio cholerae non-O1 Bangladesh. Lancet. 341:704 (letter).
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Sarkar, B.L., et al. 1993. Polymyxin B sensitive strains of Vibrio cholerae nonO1 from recent epidemic in India. Lancet. 341:1090 (letter). Bhattacharya, M.K., et al. 1993. Outbreak of Vibrio cholerae non-O1 in India and Bangladesh. Lancet. 341:1346-1347 (letter). Morris, J.G. Jr., and R.E. Black. 1985. Cholera and other vibrioses in the United States. N. Engl. J. Med. 312:343-350. Levine, M.M. 1980. Cholera in Louisiana: old problem, new light. N. Engl. J. Med. 302:345-347. Barua, D. 1992. History of cholera. In D. Barua and W.B. Greenough Ill (eds), Cholera. Plenum, New York. Faruque, S.M., et al. 1993. Clonal relationships among classical Vibrio chol-
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22, Bennish, M.L. 1994. Cholera: pathophysiology, clinical features, and treatment, p. 229-255. In I.K. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 23. Jesudason, M.V., A.M. Cherian, and T.J. John. 1993. Bloodstream invasion by Vibrio cholerae O139. Lancet 342:431. 24. Saroso, J.S., et al. 1978. A controlled field trial of plain and aluminum hydroxide-adsorbed cholera vaccines in Surabaya, Indonesia, during 19731975. Bull. World Health Organ. 56:619--627. 25. Morris, J.G., et al. 1993, Challenge and rechallenge studies with Vibrio cholerae O139 in North American volunteers. Abstracts of the 33rd Annual Meeting of the Infectious Disease Society of America, Abstract no. 231. 26. Levine, M.M., and C.O. Tackett. 1994. Recombinant live cholera vaccines, p. 395--413. In I.K. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 27. Johnson, J.A., et al, 1994. Vibrio cholerae O139 synonym Bengal is closely related to Vibrio cholerae E1 Tor but has important differences. Infect. hnmun. 62:2108-2110. 28. Hasan, J.A.K., et al. 1993. Development of rapid immunodiagnostics kits to detect Vibrio cholerae O 139 syno-
nym Bengal, p. 222. Abstracts of the 29th Joint Conference on Cholera and Related Diarrheal Diseases, The United States-Japan Cooperative Medical Science Program. 29. Kaper, J.B., A. Fasano, and M. Trucksis. 1994. Toxins of Vibrio cholerae, p. 145-176. In LK. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 30. DiRita, V.J., et al. 1991. Regulatory cascade controls virulence in Vibrio cholerae. Proc. Natl. Acad. Sci. USA. 88:5403--5407. 31. Morris, J.G. 1990, Non-O group 1 Vibrio cholerae: a look at the epidemiology of an occasional pathogen. Epidemiol. Rev. 12:179-191. 32. Waidor, M.K., and J.J. Mekalanos. 1994. Emergence of a new cholera pandemic: molecular analysis of virulence determinants in Vibrio cholerae O139 and development of a live vaccine prototype. J. Infect. Dis. 170:278-283. 33. Waidor, M.K., and J.J. Mekalanos. 1994. ToxR regulates virulence gene expression in non-O1 strains of Vibrio cholerae that cause epidemic cholera. Infect. Immun. 62:72-78. 34. Calia, K.E., et al. 1994. Comparison of Vibrio cholerae O 139 with Vibrio cholerae O1 classical and El Tor biotypes. Infect. hmnun. 62:1504-1506. 35. Weintraub, A., et al. 1994. Vibrio cholerae O139 Bengal possesses a capsular
polysaccharide which may confer increased virulence. Microb. Pathog. 16:235-241. 36. Manning, P.A., U.H. Stroeher, and R. Morona. 1994. Molecular basis for O-antigen biosynthesis in Vibrio cholerae O1: Ogawa-Inaba switching, p. 77-94. In I.K. Wachsmuth et al. (eds), Vibrio cholerae and cholera: molecular to global perspectives. ASM, Washington, D.C. 37. Waidor, M.K., R.R. Colwell, and J.J. Mekalanos. 1994. The Vibrio cholerae O139 serogroup antigen includes an Oantigen capsule and lipopolysaccharide virulence determinants. Proc. Natl. Acad. Sci. USA. 91:11388-11392. 38, Comstock, L.E., et al. 1995. The capsule and the O-antigen of Vibrio cholerae O139 Bengal are associated with a genetic region not present in Vibrio cholerae O1. Infect. Immun. 63:317323. 39. Faruque, A.S.G., et al. 1994. Studies of infection with Vibrio cholerae O 139 synonym Bengal in family contacts of index cases. Trans. R. Soc. Trop. Med. Hyg. 88:439. 40. Besser, R.E., et al. 1994. Diagnosis and treatment of cholera in the United States: are we prepared? JAMA. 272:1203-1209. 41. Swerdlow, D.S., and A.A. Ries. 1992. Cholera in the Americas: guidelines for the clinician. JAMA. 267:1495-1499.
Case Report
A Case of Bloody Diarrhea Due to Shiga-like Toxin II-Producing Escherichia coli Serotype O48:H21 Sharon L. Abbott, B.A. Microbial Diseases Laboratory Division of Communicable Disease Control California Department of Health Services Berkeley, California 94704-1011 Evangeline G. Sowers, B.S. Centers for Disease Control and Prevention Atlanta, Georgia 30333 Stojanka Aleksic, Ph.D. National Reference Center for Enteric Pathogens Institute of Hygiene Hamburg, Germany
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J. Michael Janda, Ph.D. Microbial Diseases Laboratory Division of Communicable Disease Control Berkeley, California 94704-1 O11 Enteroinvasive (EIEC) and enterohemorrhagic (EHEC) Escherichia coil are the two major groups of diarrheagenic E. coli associated with bloody diarrhea (1). Although E1EC infections are normally limited to persons returning from foreign travel, particularly from Mexico, EHEC is an emerging infectious agent in the U.S, (2). The © 1996 Elsevier Science Inc.
single most c o m m o n EHEC serotype associated with bloody diarrhea is E. coli O157:H7, responsible for >37 to 39% o f all recognized cases o f hemorrhagic colitis (3). Although the disease is benign in its early phases (secretory illness), it rapidly progresses to a more fuhninant form (colitis), which in pediatric patients may be life-threatening as a result o f the possible development o f secondary sequelae such as hemolytic uremic syndrome. Although O157:H7 is the only seroClinical Microbiology Newstetter [8:3,19q(~