- Email: [email protected]
Successful Treatment of Naegleria fowleri Meningoencephalitis by Using Intravenous Amphotericin B, Fluconazole and Rifampicin
Archives of Medical Research 36 (2005) 83–86
CASE REPORT
Successful Treatment of Naegleria fowleri Meningoencephalitis by Using Intravenous Amphotericin B, Fluconazole and Rifampicin Jesu´s Vargas-Zepeda,a Alejandro V. Go´mez-Alcala´,b Jose´ Alfonso Va´zquez-Morales,a Leonardo Licea-Amaya,c Johan F. De Jonckheered and Fernando Lares-Villae a
Department of Pediatrics, Hospital de Especialidades 1, Centro Me´dico Nacional Noroeste, Instituto Mexicano del Seguro Social, Ciudad Obrego´n, Sonora, Me´xico b Board of Medical Research, Delegacio´n Sonora, Instituto Mexicano del Seguro Social, Ciudad Obrego´n, Sonora, Me´xico c Clinical Laboratory, Hospital de Especialidades 1, Centro Me´dico Nacional Noroeste, Instituto Mexicano del Seguro Social, Ciudad Obrego´n, Sonora, Me´xico d Research Institute for Tropical Diseases, Christian de Duve Institute of Cellular Pathology, Brussels, Belgium e Department of Biotechnology and Alimentary Sciences, Instituto Tecnolo´gico de Sonora, Ciudad Obrego´n, Sonora, Me´xico Received for publication June 22, 2004; accepted October 22, 2004 (04/013).
Background. Primary amebic meningoencephalitis (PAM) is an emerging disease with a rapidly fatal outcome. Only eight reports of cured cases have appeared in the medical literature to date. Methods. A 10-year-old boy developed PAM caused by Naegleria fowleri 1 week after swimming in an irrigation canal. He was admitted to our hospital after 9 h of severe headache and vomiting, fever, ataxic gait, mild confusion, and seizures were evident. Trophozoites were identified in the cerebrospinal fluid (CSF). Treatment with intravenous (i.v.) dexamethasone, amphotericin B, fluconaloze, and oral rifampicin was started. After several hours of conflicting clinical signs, recovery began, and on the third day he was conscious again. Hospital discharge occurred on day 23, after a normal brain CT scan. There was no sequel to the disease during the following 12 months. Results. The amebas present in the CSF were identified and confirmed as N. fowleri after observation of wet mounts and of cultures seeded on 1.5% non-nutrient agar plates covered with Escherichia coli, vegetative and cystic forms, enflagellation experiments in distilled water at 98⬚F, temperature tolerance testing and by indirect immunofluorescence using N. fowleri LEE antibody. The genotype was determined by PCR amplification and sequencing of the internal transcribed spacers (ITS) including the 5.8S rDNA. Conclusions. Early treatment of PAM by i.v. administration of amphotericin B and fluconazole, and oral administration of rifampicin can offer some hope of cure for this devastating disease. 쑖 2005 IMSS. Published by Elsevier Inc. Key Words: Naegleria fowleri, Free-living ameba, Primary amebic meningoencephalitis, Meningoencephalitis, Water-borne infections.
Introduction Primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri is a generally fatal disease which develops in individuals who in the previous few days swam in bodies of water containing this free-living ameba (FLA) (1). Address reprint requests to: Dr. Alejandro V. Go´mez-Alcala´, Coordinacio´n Delegacional de Investigacio´n en Salud, Delegacio´n Estatal del IMSS, Sonora, 5 de Febrero 205, Centro, Ciudad Obrego´n, Sonora, Me´xico CP 85000. E-mail: [email protected]
0188-4409/05 $–see front matter. Copyright d o i : 1 0 .1 0 16 / j . a rc m e d .2 00 4 .1 1 .0 03
Even though PAM is still considered a rare disorder, the number of reports increases each year, with a fatal outcome in almost all cases. We have compiled only eight reports in which a cure was achieved (2–9), but for several of these it is debatable whether they were really caused by N. fowleri (10). In Mexico, there have been over 25 confirmed cases, most in the northwestern region of the country (11) with only one successfully treated case recorded (12). Amphotericin B remains the cornerstone of treatment, alone or in combination with other drugs (13), but no drugs
쑖 2005 IMSS. Published by Elsevier Inc.
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Vargas-Zepeda et al. / Archives of Medical Research 36 (2005) 83–86
have been scientifically validated yet because of the low incidence and rapidly fatal course of this disease. Here we report a recent case of PAM that we had the opportunity to treat at a very early stage, leading to complete recovery of our patient. Patients and Methods A 10-year-old previously healthy boy was admitted to the emergency room in April 2003 with persistent severe headache, vomiting, and fever. One week before, he had been swimming in a nearby irrigation canal. He was well until 6:00 a.m. on the day of his admission, when headache, vomiting, and high fever started sequentially. Penicillin and aspirin were administered but a few hours later, as his symptoms worsened, the boy was taken to our hospital. At 3:00 p.m. he was examined in the emergency room and exhibited unequivocal signs of meningitis: fever of 102⬚F, ataxic gait, uncoordinated movements, mild confusion, and generalized seizures. His blood tests showed 29,000 leukocytes/mm3 with 91% granulocytes and 3% bands. A lumbar puncture revealed a cloudy cerebrospinal fluid (CSF), analysis (at about 8:00 p.m.) showed glucose 73 mg/dl, protein 40 mg/dl, and marked pleocytosis with 90% granulocytes and “ameba-like structures” in the centrifuged wet mount. The latter finding raised the suspicion of PAM, and treatment was begun with dexamethasone 0.6 mg/k/day, every 6 h intravenously (i.v.), ceftriaxone 100 mg/k/day, every 8 h i.v., rifampicin 10 mg/ k/day, every 24 h p.o., and amphotericin B 0.25 mg/k/day, every 24 h i.v. (daily 0.25 mg/k increasing dosage up to 1 mg/k/day). The next day at 8:00 a.m., fluconazole administration was started at a dose of 10 mg/k/day, every 24 h i.v. The next doses were given p.o. because our stock of the i.v. vial was exhausted. At about 2:00 p.m., almost 24 h after admission, the boy’s condition worsened, and he required ventilatory support. A new spinal tap was performed, and the fluid generated almost the same data as previously. The presence of living amebas was confirmed. No changes were made to the therapeutic regime. The next day, at 8:00 a.m., 40 h after admission, the boy was observed to be in a markedly better condition, afebrile, with eyes wide open and performing voluntary movements to decannulate himself, which later proved successful. No reintubation was required and, at about 10:00 a.m., he even asked for food. He improved rapidly, and on day 6 he was able to sit and eat by himself, and nuchal rigidity vanished. At day 10 he was able to walk without help and neuropathological signs were no longer observed. Amphotericin B treatment was maintained for 14 days, and administration of rifampicin and fluconazole p.o. was continued for 1 month. At day 22 a brain CAT scan showed no abnormality. He was discharged from the hospital the next day, and during the next 12 months he was followed as an outpatient, with no apparent recurrence of disease.
Results Amebas were observed by light microscopy in wet mounts of CSF and cultures were obtained when CSF was seeded onto 1.5% non-nutrient agar plates covered with Escherichia coli (Figure 1). Identification to the level of genus was achieved by observation of the vegetative and cystic forms of the ameba as well as by enflagellation experiments in distilled water at 98⬚F. To assess high temperature tolerance of the ameba, cultures were incubated at 113⬚F in a humidified atmosphere and examined (14). Confirmation that the ameba was N. fowleri was achieved by indirect immunofluorescence using an N. fowleri LEE antibody. The genotype was determined by PCR amplification and sequencing of the internal transcribed spacers (ITS), including the 5.8S rDNA (16). The strain belongs to one of the two common genotypes present in the U.S.
Discussion PAM is a central nervous system (CNS) infection caused by FLA. It is characterized by a purulent, necrotizing hemorrhagic inflammation involving mainly the base of the brain and meninges and has an exceedingly high mortality rate. With over 350 cases of CNS infection due to FLA reported to date (15), increased awareness has slowly developed among clinicians; nevertheless, over 95% of diagnosed patients die, most deaths due to late diagnosis and treatment. Extensive research on FLA biology has been conducted over the last few years (16). FLA are ubiquitous but, for unknown reasons, infections are extremely rare. In the U.S. during 1991–2000, 21 cases of PAM were reported (17–21), all caused by N. fowleri and most from the southern states. N. fowleri lives in warm fresh water, gaining access to the CNS through the nasal mucosa, the cribiform plate, and the olfactory nerves (22). Northwestern Mexico is also a
Figure 1. Cluster of axenic culture of N. fowleri isolated from CSF of our patient showing a karyosome that is surrounded by a clear nuclear halo (thin arrow) and a prominent ectoplasmic pseudopod (thick arrow).
A Survival Case of Naegleria fowleri Meningoencephalitis
region in which FLA find favorable environmental conditions for survival leading to the wide distribution of thermophilic ameba within natural and artificial ponds, irrigation canals, and even swimming pools (23⫺25). Lares-Villa has compiled details of more than 25 cases of PAM in this region (11). Our patient came from a small town in the Yaqui River valley in Sonora, Mexico. Irrigation canals run through this town and, in a previous study, N. fowleri was cultivated from water collected from these canals and even from water from pipelines supplied by the municipality (26). The boy developed typical PAM 1 week after swimming in a canal, which is also a typical incubation period for this disease. The observation of ameba-like structures in the CSF was the key point in this boy’s outcome, allowing us to make the proper adjustments to his treatment, with an early start of the triple drug regime and of the necessary procedures to isolate, preserve, and classify the ameba. We believe that the addition of i.v. fluconazole to the widely accepted therapeutic regime of i.v. amphotericin B with or without oral rifampicin (3,4,6,13) was the crucial clinical decision. Imidazoles have shown significant activity against FLA (27), and fluconazole (in particular) has been proven to penetrate the blood-brain barrier remarkably well (28,29). Fluconazole has also shown an unexpected effectiveness for reducing organ dysfunction and mortality in septic shock, probably by increasing bactericidal activity and the recruitment of neutrophils (30). Obviously the other agents used to treat this boy were also beneficial, and a synergistic effect between amphotericin B and fluconazole can even be alleged, as previously demonstrated against other infective agents (31). Intrathecal amphotericin B, which has also been recommended, was deferred in case our patient’s condition did not improve during the first 48 h. The pathogenic species N. fowleri consists of different genotypes that are characterized by different lengths of the ITS1 sequence (16). However, no difference in virulence is detected between the different genotypes. The isolate from our patient belongs to a genotype that is commonly found in American PAM patients who have died. Therefore, the recovery of this patient was not due to the low pathogenicity of the infecting N. fowleri strain. However, prior to the case presented here, the only N. fowleri strain that has been isolated from a surviving patient (7) was found to represent a novel genotype (32). An increased state of awareness of PAM is needed among lab technicians and emergency room doctors if the rapidity of diagnosis of future cases is to be increased and the effectiveness of treatment improved. Early diagnosis and treatment with a triple drug regime of i.v. amphotericin B, i.v. fluconazole, and oral rifampicin resulted in a successful outcome for this patient, although more evidence is required before we can make a definitive recommendation for this treatment regime.
85
Acknowledgments We thank our medical lab technician, Lourdes Lara-Alcaraz, for accurate microscopic observations, Rau´l Holguı´n-Soto, MSc. for high quality of care of the cultures of these amebae, Dr. Fernando Lara for his help in the follow-up of this case, and Dr. Anthony Newsome from Middle Tennessee State University for providing us with the LEE Naegleria fowleri antibody. We also thank Dr. Susan Brown for correcting the grammar and spelling.
References 1. Parija SC, Jayakeerthee SR. Naegleria fowleri: a free living amoeba of emerging medical importance. J Commun Dis 1999;31:153–159. 2. Jain R, Prabhakar S, Modi M, Bhatia R, Sehgal R. Naegleria meningitis: a rare survival. Neurol India 2002;50:470–472. 3. Wang A, Kay R, Poon WS, Ng HK. Successful treatment of amoebic meningoencephalitis in Chinese living in Hong Kong. Clin Neurol Neurosurg 1993;95:249–252. 4. Loschiavo F, Ventura-Spagnolo T, Sessa E, Bramanti P. Acute primary meningoencephalitis from entamoeba Naegleria fowleri. Report of a clinical case with a favourable outcome. Acta Neurol (Napoli) 1993; 15:333–340. 5. Poungvarin N, Jariya P. The fifth non-lethal case of primary amoebic meningoencephalitis. J Med Assoc Thai 1991;74:112–115. 6. Brown RL. Successful treatment of primary amebic meningoencephalitis. Arch Intern Med 1991;151:1201–1202. 7. Seidel JS, Harmatz P, Visvesvara GS, Cohen A, Edwards J, Turner J. Successful treatment of primary amebic meningoencephalitis. N Engl J Med 1982;306(6):346–348. 8. Anderson K, Jamieson A, Jadin JB, Willaert E. Primary amoebic meningoencephalitis. Lancet 1973;1(7804):672. 9. Apley J, Clarke SK, Roome AP, Sandry SA, Saygi G, Silk B, Warhurst DC. Primary amoebic meningoencephalitis in Britain. Br Med J 1970; 1(696):596–599. 10. Martinez AJ. Amebic encephalitis unlikely. Arch Intern Med 1992; 152:1330–1331. 11. Lares-Villa F. Free-living amoebae infections in Mexico. Proc. IX International Meeting on the Biology and Pathogenicity on Free-Living Amoebae. Billot-Bonef S, Cabanes PA, Marciano-Cabral F, Pernin P, Pringuez E, eds. Paris: Editions John Libbey Eurotext;2001. pp. 13–18. 12. Rodrı´guez Pe´rez EG. Meningoencefalitis por Naegleria fowleri, informe de un caso. Infectologı´a (Me´x) 1984;4:263–266. 13. Goswick SM, Brenner GM. Activities of therapeutic agents against Naegleria fowleri in vitro and in a mouse model of primary amebic meningoencephalitis. J Parasitol 2003;89:837–842. 14. Schuster FL. Cultivation of pathogenic and opportunistic free-living amebas. Clin Microbiol Rev 2002;15:342–354. 15. Martı´nez AJ. Free-living amebas and the immune deficient host. Proc. IX International Meeting on the Biology and Pathogenicity on FreeLiving Amoeba. Billot-Bonef S, Cabanes PA, Marciano-Cabral F, Pernin P, Pringuez E, eds. Paris: Editions John Libbey Eurotext;2001. pp. 1–12. 16. De Jonckheere JF. A century of research on the amoeboflagellate genus Naegleria. Acta Protozool 2002;41:309–342. 17. Lee SH, Levy DA, Craun GF, Beach MJ, Calderon RL. Surveillance for waterborne-disease outbreaks—United States, 1999-2000. MMWR 2002;51(SS-08):1–28. 18. Barwick RS, Levy DA, Craun GF, Beach MJ, Calderon RL. Surveillance for waterborne disease outbreaks—United States, 1997-1998. MMWR 2000;49(SS-04):1–35. 19. Levy DA, Bens MS, Craun GF, Calderon RL, Herwaldt BL. Surveillance for waterborne disease outbreaks—United States, 1995-1996. MMWR 1998;47(SS-5):1–34.
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20. Kramer MH, Herwaldt BL, Craun GF, Calderon RL, Juranek DD. Surveillance for waterborne disease outbreaks—United States, 19931994. MMWR 1996;45(SS-1):1–33. 21. Anon. Surveillance for waterborne disease outbreaks—United States, 1991-1992. MMWR 1993;42(SS-05):1–22. 22. Jarolim KL, McCosh JK, Howard MJ, John DT. A light microscopy study of the migration of Naegleria fowleri from the nasal submucosa to the central nervous system during the early stage of primary amebic meningoencephalitis in mice. J Parasitol 2000;86:50–55. 23. Lares-Villa F, Guerrero-Dumas AM, Lo´pez-Osorio A. Estudio protozoolo´gico (Subphylum SARCODINA, Clase LOBOSEA) en ambientes acua´ticos de la regio´n del Valle del Yaqui, Sonora, Me´xico. ITSONDIEP (Mex) 1997;2:47–55. 24. Visvesvara GS, Stehr-Green JK. Epidemiology of free-living ameba infections. J Protozool 1990;37(suppl):25S–33S. 25. John DT, Howard MJ. Seasonal distribution of pathogenic free-living amebae in Oklahoma waters. Parasitol Res 1995;81:193–201. 26. Herrera-Andrade MH, Morales-Campoy EC, Lares-Villa F, Holguı´nSoto R. Estudio de la presencia de amibas de vida libre en agua entubada de la localidad de San Ignacio Rı´o Muerto, Sonora. En: Memorias
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de la VIII Reunio´n de Investigacio´n en Salud en el Estado de Sonora. Acta Me´d Sonora (Mex) 2002;2:33–34. Thong YH, Rowan-Kelly B, Shepherd C, Ferrante A. Growth inhibition of Naegleria fowleri by tetracycline, rifamycin, and miconazole. Lancet 1977;2(8043):876. Mian UK, Mayers M, Garg Y, Liu QF, Newcomer G, Madu C, Liu W, Louie A, Miller MH. Comparison of fluconazole pharmacokinetics in serum, aqueous humor, vitreous humor, and cerebrospinal fluid following a single dose and at steady state. J Ocul Pharmacol Ther 1998;14:459–471. Yang H, Wang Q, Elmquist WF. Fluconazole distribution to the brain: a crossover study in freely-moving rats using in vivo microdialysis. Pharm Res 1996;13:1570–1575. Jacobs S, Price Evans DA, Tariq M, Al Omar NF. Fluconazole improves survival in septic shock: a randomized double-blind prospective study. Crit Care Med 2003;31:1938–1946. Clark AB, Lobo BL, Gelfand MS. Fluconazole and amphotericin B for cryptococcal meningitis. Ann Pharmacother 1996;30:1408–1410. Zhou L, Sriram R, Visvesvara GS, Xiao L. Genetic variations in the internal transcribed spacer and mitochondrial small subunit rRNA gene of Naegleria spp. J Eukaryot Microbiol 2003;50(suppl):522–526.
CASE REPORT
Successful Treatment of Naegleria fowleri Meningoencephalitis by Using Intravenous Amphotericin B, Fluconazole and Rifampicin Jesu´s Vargas-Zepeda,a Alejandro V. Go´mez-Alcala´,b Jose´ Alfonso Va´zquez-Morales,a Leonardo Licea-Amaya,c Johan F. De Jonckheered and Fernando Lares-Villae a
Department of Pediatrics, Hospital de Especialidades 1, Centro Me´dico Nacional Noroeste, Instituto Mexicano del Seguro Social, Ciudad Obrego´n, Sonora, Me´xico b Board of Medical Research, Delegacio´n Sonora, Instituto Mexicano del Seguro Social, Ciudad Obrego´n, Sonora, Me´xico c Clinical Laboratory, Hospital de Especialidades 1, Centro Me´dico Nacional Noroeste, Instituto Mexicano del Seguro Social, Ciudad Obrego´n, Sonora, Me´xico d Research Institute for Tropical Diseases, Christian de Duve Institute of Cellular Pathology, Brussels, Belgium e Department of Biotechnology and Alimentary Sciences, Instituto Tecnolo´gico de Sonora, Ciudad Obrego´n, Sonora, Me´xico Received for publication June 22, 2004; accepted October 22, 2004 (04/013).
Background. Primary amebic meningoencephalitis (PAM) is an emerging disease with a rapidly fatal outcome. Only eight reports of cured cases have appeared in the medical literature to date. Methods. A 10-year-old boy developed PAM caused by Naegleria fowleri 1 week after swimming in an irrigation canal. He was admitted to our hospital after 9 h of severe headache and vomiting, fever, ataxic gait, mild confusion, and seizures were evident. Trophozoites were identified in the cerebrospinal fluid (CSF). Treatment with intravenous (i.v.) dexamethasone, amphotericin B, fluconaloze, and oral rifampicin was started. After several hours of conflicting clinical signs, recovery began, and on the third day he was conscious again. Hospital discharge occurred on day 23, after a normal brain CT scan. There was no sequel to the disease during the following 12 months. Results. The amebas present in the CSF were identified and confirmed as N. fowleri after observation of wet mounts and of cultures seeded on 1.5% non-nutrient agar plates covered with Escherichia coli, vegetative and cystic forms, enflagellation experiments in distilled water at 98⬚F, temperature tolerance testing and by indirect immunofluorescence using N. fowleri LEE antibody. The genotype was determined by PCR amplification and sequencing of the internal transcribed spacers (ITS) including the 5.8S rDNA. Conclusions. Early treatment of PAM by i.v. administration of amphotericin B and fluconazole, and oral administration of rifampicin can offer some hope of cure for this devastating disease. 쑖 2005 IMSS. Published by Elsevier Inc. Key Words: Naegleria fowleri, Free-living ameba, Primary amebic meningoencephalitis, Meningoencephalitis, Water-borne infections.
Introduction Primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri is a generally fatal disease which develops in individuals who in the previous few days swam in bodies of water containing this free-living ameba (FLA) (1). Address reprint requests to: Dr. Alejandro V. Go´mez-Alcala´, Coordinacio´n Delegacional de Investigacio´n en Salud, Delegacio´n Estatal del IMSS, Sonora, 5 de Febrero 205, Centro, Ciudad Obrego´n, Sonora, Me´xico CP 85000. E-mail: [email protected]
0188-4409/05 $–see front matter. Copyright d o i : 1 0 .1 0 16 / j . a rc m e d .2 00 4 .1 1 .0 03
Even though PAM is still considered a rare disorder, the number of reports increases each year, with a fatal outcome in almost all cases. We have compiled only eight reports in which a cure was achieved (2–9), but for several of these it is debatable whether they were really caused by N. fowleri (10). In Mexico, there have been over 25 confirmed cases, most in the northwestern region of the country (11) with only one successfully treated case recorded (12). Amphotericin B remains the cornerstone of treatment, alone or in combination with other drugs (13), but no drugs
쑖 2005 IMSS. Published by Elsevier Inc.
84
Vargas-Zepeda et al. / Archives of Medical Research 36 (2005) 83–86
have been scientifically validated yet because of the low incidence and rapidly fatal course of this disease. Here we report a recent case of PAM that we had the opportunity to treat at a very early stage, leading to complete recovery of our patient. Patients and Methods A 10-year-old previously healthy boy was admitted to the emergency room in April 2003 with persistent severe headache, vomiting, and fever. One week before, he had been swimming in a nearby irrigation canal. He was well until 6:00 a.m. on the day of his admission, when headache, vomiting, and high fever started sequentially. Penicillin and aspirin were administered but a few hours later, as his symptoms worsened, the boy was taken to our hospital. At 3:00 p.m. he was examined in the emergency room and exhibited unequivocal signs of meningitis: fever of 102⬚F, ataxic gait, uncoordinated movements, mild confusion, and generalized seizures. His blood tests showed 29,000 leukocytes/mm3 with 91% granulocytes and 3% bands. A lumbar puncture revealed a cloudy cerebrospinal fluid (CSF), analysis (at about 8:00 p.m.) showed glucose 73 mg/dl, protein 40 mg/dl, and marked pleocytosis with 90% granulocytes and “ameba-like structures” in the centrifuged wet mount. The latter finding raised the suspicion of PAM, and treatment was begun with dexamethasone 0.6 mg/k/day, every 6 h intravenously (i.v.), ceftriaxone 100 mg/k/day, every 8 h i.v., rifampicin 10 mg/ k/day, every 24 h p.o., and amphotericin B 0.25 mg/k/day, every 24 h i.v. (daily 0.25 mg/k increasing dosage up to 1 mg/k/day). The next day at 8:00 a.m., fluconazole administration was started at a dose of 10 mg/k/day, every 24 h i.v. The next doses were given p.o. because our stock of the i.v. vial was exhausted. At about 2:00 p.m., almost 24 h after admission, the boy’s condition worsened, and he required ventilatory support. A new spinal tap was performed, and the fluid generated almost the same data as previously. The presence of living amebas was confirmed. No changes were made to the therapeutic regime. The next day, at 8:00 a.m., 40 h after admission, the boy was observed to be in a markedly better condition, afebrile, with eyes wide open and performing voluntary movements to decannulate himself, which later proved successful. No reintubation was required and, at about 10:00 a.m., he even asked for food. He improved rapidly, and on day 6 he was able to sit and eat by himself, and nuchal rigidity vanished. At day 10 he was able to walk without help and neuropathological signs were no longer observed. Amphotericin B treatment was maintained for 14 days, and administration of rifampicin and fluconazole p.o. was continued for 1 month. At day 22 a brain CAT scan showed no abnormality. He was discharged from the hospital the next day, and during the next 12 months he was followed as an outpatient, with no apparent recurrence of disease.
Results Amebas were observed by light microscopy in wet mounts of CSF and cultures were obtained when CSF was seeded onto 1.5% non-nutrient agar plates covered with Escherichia coli (Figure 1). Identification to the level of genus was achieved by observation of the vegetative and cystic forms of the ameba as well as by enflagellation experiments in distilled water at 98⬚F. To assess high temperature tolerance of the ameba, cultures were incubated at 113⬚F in a humidified atmosphere and examined (14). Confirmation that the ameba was N. fowleri was achieved by indirect immunofluorescence using an N. fowleri LEE antibody. The genotype was determined by PCR amplification and sequencing of the internal transcribed spacers (ITS), including the 5.8S rDNA (16). The strain belongs to one of the two common genotypes present in the U.S.
Discussion PAM is a central nervous system (CNS) infection caused by FLA. It is characterized by a purulent, necrotizing hemorrhagic inflammation involving mainly the base of the brain and meninges and has an exceedingly high mortality rate. With over 350 cases of CNS infection due to FLA reported to date (15), increased awareness has slowly developed among clinicians; nevertheless, over 95% of diagnosed patients die, most deaths due to late diagnosis and treatment. Extensive research on FLA biology has been conducted over the last few years (16). FLA are ubiquitous but, for unknown reasons, infections are extremely rare. In the U.S. during 1991–2000, 21 cases of PAM were reported (17–21), all caused by N. fowleri and most from the southern states. N. fowleri lives in warm fresh water, gaining access to the CNS through the nasal mucosa, the cribiform plate, and the olfactory nerves (22). Northwestern Mexico is also a
Figure 1. Cluster of axenic culture of N. fowleri isolated from CSF of our patient showing a karyosome that is surrounded by a clear nuclear halo (thin arrow) and a prominent ectoplasmic pseudopod (thick arrow).
A Survival Case of Naegleria fowleri Meningoencephalitis
region in which FLA find favorable environmental conditions for survival leading to the wide distribution of thermophilic ameba within natural and artificial ponds, irrigation canals, and even swimming pools (23⫺25). Lares-Villa has compiled details of more than 25 cases of PAM in this region (11). Our patient came from a small town in the Yaqui River valley in Sonora, Mexico. Irrigation canals run through this town and, in a previous study, N. fowleri was cultivated from water collected from these canals and even from water from pipelines supplied by the municipality (26). The boy developed typical PAM 1 week after swimming in a canal, which is also a typical incubation period for this disease. The observation of ameba-like structures in the CSF was the key point in this boy’s outcome, allowing us to make the proper adjustments to his treatment, with an early start of the triple drug regime and of the necessary procedures to isolate, preserve, and classify the ameba. We believe that the addition of i.v. fluconazole to the widely accepted therapeutic regime of i.v. amphotericin B with or without oral rifampicin (3,4,6,13) was the crucial clinical decision. Imidazoles have shown significant activity against FLA (27), and fluconazole (in particular) has been proven to penetrate the blood-brain barrier remarkably well (28,29). Fluconazole has also shown an unexpected effectiveness for reducing organ dysfunction and mortality in septic shock, probably by increasing bactericidal activity and the recruitment of neutrophils (30). Obviously the other agents used to treat this boy were also beneficial, and a synergistic effect between amphotericin B and fluconazole can even be alleged, as previously demonstrated against other infective agents (31). Intrathecal amphotericin B, which has also been recommended, was deferred in case our patient’s condition did not improve during the first 48 h. The pathogenic species N. fowleri consists of different genotypes that are characterized by different lengths of the ITS1 sequence (16). However, no difference in virulence is detected between the different genotypes. The isolate from our patient belongs to a genotype that is commonly found in American PAM patients who have died. Therefore, the recovery of this patient was not due to the low pathogenicity of the infecting N. fowleri strain. However, prior to the case presented here, the only N. fowleri strain that has been isolated from a surviving patient (7) was found to represent a novel genotype (32). An increased state of awareness of PAM is needed among lab technicians and emergency room doctors if the rapidity of diagnosis of future cases is to be increased and the effectiveness of treatment improved. Early diagnosis and treatment with a triple drug regime of i.v. amphotericin B, i.v. fluconazole, and oral rifampicin resulted in a successful outcome for this patient, although more evidence is required before we can make a definitive recommendation for this treatment regime.
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Acknowledgments We thank our medical lab technician, Lourdes Lara-Alcaraz, for accurate microscopic observations, Rau´l Holguı´n-Soto, MSc. for high quality of care of the cultures of these amebae, Dr. Fernando Lara for his help in the follow-up of this case, and Dr. Anthony Newsome from Middle Tennessee State University for providing us with the LEE Naegleria fowleri antibody. We also thank Dr. Susan Brown for correcting the grammar and spelling.
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