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A report of a further hospital outbreak caused by a multi-resistant Acinetobacter anitratus
Journal of Hospital Infection (1982) 3, 305-309
SHORT REPORT
A report of a further hospital outbreak!caused by a multi-resistant Acinetobacter anitratus J. Holton The Middlesex Hospital Medical School, London Wl Introduction
Acinetobacter anitratus has been shown to be the cause of a number of serious infections. There have been reports of it causing endocarditis (Pal, Sujatha and Kale, 1981), meningitis (Ghoneim and Halaka, 1980), pneumonia (Rudin, Michael and Huxley, 1979), and abscesses(Robinson, Garrison and Brown, 1964). It is widely spread in nature being isolated from water, soil and sewage (Henriksen, 1973), and has also been isolated from skin (Taplin, Rebel1 and Zaiaz, 1963). It is a particular risk to debilitated patients and is a recognized hospital-associated pathogen. The epidemiology of hospital outbreaks is not fully understood, although respirometers (Cunha et al., 1980) and humidifiers have been implicated as reservoirs for the organism. Cross-contamination via the hands has been regarded as a possible route of transmission (French et al., 1980). The organism usually shows resistance to ampicillin, cephalothin and chloramphenicol, but is sensitive to the aminoglycosides, sulphonamides, tetracyclines, ureidopenicillins and the third generation cephalosporins (Retailliau et al., 1979; Daschner and Nopper, 1980; Appelbaum et al., 1981). There has been one report of a multi-resistant Acinetobutter spp. causing an outbreak in a urology ward (French et al., 1980). The organism was resistant to 18 antibiotics, being sensitive only to nalidixic acid, colistin, tobramycin and amikacin. A similar outbreak occurred in a surgical intensive care unit (Castle et al., 1978). I report here a further outbreak. Methods and materials
Routine bacteriology specimens were collected over a two-year period (1980-81) and a search made for the typical mucoid, butyrous, domed shaped colonies of A. utitrut2Ls. Suspect colonies were Gram stained and oxidase and motility tests were performed. Full identification was made using API20E. Initial sensitivities were performed by disc diffusion using Stoke’s method. MICs were determined by both the agar dilution method (Oxoid DST agar CM26) using a Steers replicator on all 58 isolates, and on 10 of the isolates by the broth dilution method (Oxoid nutrient broth CMI); an inoculum of 10” cells/ml was used in each case. 0 1982The Hospital Infection Society 0195-6701/82/030305 + 0.5$oz.oo/o 305
J. Holton
306
Soap tolerance was determined using the method of Billings (1965), gelatinase production by the method of Fraser (Cowan and Steel, 1975) and any plasmids were searched for using the technique of Birnboim and Doly (1979) and caesium chloride ultra-centrifugation. The DNA for this latter method was extracted from 100 ml of an overnight culture of acinetobacter by the method of Marmur (1961). Results Over a period of two years there were 58 separate isolates of Acinetobacter spp. Repeat isolates from the same patient were ignored. Most isolates (20) were from sputum, 18 from wound swabs, 14 from urine, five from bile and one from blood culture. Their distribution over the period of study is shown in Figure 1, which reveals a seasonal periodicity, most isolates being found in autumn and winter. Six of the isolates were A. lwoj?I, the remainder were A. anitratus. Of the 52 A. anitratus strains, eight (15 per cent) produced a gelatinase, 35 (67 per cent) grew at 43 “C, all were intolerant of 10 per cent soap and only three isolates grew on 5 per cent soap. A plasmid could not be detected in any of the isolates.
IO 9 P z 0 .2 : =; 5 2
s 7 6 5 4 3 2 1 0 Jan.
Feb. Mm. Apr May
Jam Jul.
Aug.
Sq. Oct. Nov. Dec. Jon. Fab. MO. Apr. May Month
Figure
1. Monthly
distribution
of
Jun. Jul.
Aug
Se,,. Cm.
Nov.
De,
isolation
of isolation
of Acinetobacter strains.
The distribution of MICs demonstrated as ubpopulation that was multiresistant showing resistance to > 256 mg/l of ampicillin, carbenicillin, ticarcillin, mezlocillin, cefoxitin, cefotaxime and gentamicin. These isolates, 34 in number, were also resistant to cefuroxime (> 128 mg/l) and chloramphenicol(64 mg/l) but did not show a bimodal distribution. They were also resistant to trimethoprim, sulphonamide, tetracycline and nitrofurantoin. All isolates were sensitive to nalidixic acid, tobramycin and amikacin. All were soap intolerant, grew at 43 “C and did not produce a gelatinase.
Outbreak
of multi-resistant
A. anitratus
307
The antibiotic resistant organism was isolated from 13 different wards, of which 24/34 (70 per cent) were isolated from five surgical wards and 11/24 of these (46 per cent) on two urological wards. Of the 11 isolates from urological wards, seven were from urine. All of these seven patients had at some time been catheterized. Thirteen isolates occurred on other surgical wards, nine of which were isolated from swabs. Ten were isolated from medical wards, seven of which were from sputa. On the urological wards there were two periods in which the isolates were consecutive. In one instance the same bed was used by two patients, both of whom acquired the multi-resistant organism. Environmental sampling on this ward revealed acinetobacter in the plastic urinals in the sluice, but the bacterium was not found in the ward, bed linen or bed frames. Three of 20 staff carried the acinetobatter on their hands. Sampling of staff on wards not affected demonstrated that two out of 40 carried acinetobacter on their hands, but it was not multiresistant. None of the seven patients had acinetobacter in their faeces and the sampling of 30 faeces from patients on unaffected wards yielded a similar negative result. The patients were isolated, but this did not prevent the appearance of more cases throughout the hospital. The nurses were advised to pay strict attention to handwashing and when changing catheter bags to wear disposable gloves. The plastic urinals were disinfected. After disinfection acinetobacter was not isolated from them. In three cases transfer of patients from infected wards to non-infected wards was associated with further cases in the previously non-infected wards. In two cases patients who were transferred from non-infected wards to infected wards acquired the resistant acinetobacter. A retrospective analysis of nurse and domestic movement could not account for the occurrence throughout the hospital. It was not possible to trace other staff movement in the hospital. After the introduction of strict hygiene measures when touching infected patients or infected materials the epidemic organism was gradually lost from the hospital and has not been re-isolated in the past six months. In this period there have been only three acinetobacter isolates, none of them multi-resistant. Discussion Acinetobacter is an organism normally, although not exclusively, thought of as a nosocomial pathogen affecting debilitated patients. It is usually susceptible to a number of antibiotics. Recently, however, several reports have highlighted multiresistant acinetobacter as an important cause of hospital infection. An organism isolated during the present study seems to be similar to one isolated from another London hospital. It is multi-resistant, grows at 43 “C, is tolerant of soap and does not seem to carry any plasmids to account for the drug resistance. Plasmids have been detected in Acz?zetobacte~spp. and one self-transmissible plasmid has been shown to determine sulphonamide resistance (Hinchliffe and Vivian, 1980). The inability to isolate a plasmid in these particular organisms does not imply the resistance genes are necessarily chromosomally located.
308
J. Holton
With the lack of any effective typing system for Acinetobacter spp. there is no proof that this organism constitutes an epidemic strain even though all the isolates had several factors in common. Further progress in understanding the epidemiology of acinetobacter outbreaks requires the development of a typing system. The outbreak followed a seasonalpattern, an effect which has been noted previously and to which there is no ready explanation. Of the 58 people from which acinetobacter was isolated, 10 people died, and of these the cause of death could be directly attributed to an infection with the organism in three. All these patients were compromised in some way and all died of pneumonia. The source of the organism was not established. It would seem that faeces was not an important reservoir, as it is for other hospital associatedbacteria and that the likely source was the skin of both patients and staff. It is very likely that the plastic urinals were secondarily contaminated. It would seem that movement of patients from ward to ward did spread the strain, but isolation of infected patients did not prevent further casesoccurring in the short term. It is possible that transmission of the organism did occur with movement of staff and the finding of the resistant acinetobacter on the hands of staff would support this. A combination of source isolation and the wearing of gloves when handling infected material prevented further casesfrom occurring. Its role as an opportunist is exemplified by its site of localization. The majority of infections occurred on urology wards and in patients that had been catheterized, although several infections also occurred in wounds on surgical wards and in the lungs of immunocompromised patients. References Appelbaum, P. C., Tamim, J., Stavitz, J. & Aber, R. C. (1981). Sensitivity of Acinetobacter calcoaceticus strains to seven cephalosporins. Lancet ii, 472. Billings, E. (1955). Studies on a soap tolerant organism: a new variety of Bacterium anitratum. Journal of General Microbiology 13, 252-260. Birnboim, H. & Doly, J. (1979). A rapid alkaline extraction procedure for screening recombinant plasmid DNA. Nucleic Acid Research 7, 1513-1523. Castle, M., Tenney, J. H., Weinstein, M. D. & Eickhoff, H. C. (1978). Outbreak of multiply resistant Acinetobacter in a surgical intensive care unit: epidemiology and control. Heart and Lung 7, 641-644. Cowan, S. T. & Steel, K. J. (1975). Manual for the Identification of Medical Bacteria, 2nd edn. Cambridge University Press. Cunha, B. A., Klimek, J. J., Gracewski, J., McLaughlin, J. C. & Quintiliani, R. (1980). A common source outbreak of Acinetobacter pulmonary infections traced to Wright respirometers. Postgraduate Medical Journal 56, 169-173. Daschner, F. & Nopper, S. (1980). Susceptibility of nosocomial Acinetobacter anitratus strains to 14 antibiotics. Journal of Antimicrobial Chemotherapy 6, 415-416. French, G. L., Casewell, M. W., Roncoroni, A. J., Knight, S. & Phillips, I. (1980). A hospital outbreak of antibiotic-resistant Acinetobacter anitratus : epidemiology and control. Journal of Hospital Infection 1, 125-131. Ghoneim, A. T. M. & Halaka, A. (1980). Meningitis due to Acinetobacter calcoaceticus variant anitratus. Journal of Hospital Infection 1, 359-361. Henriksen, S. D. (1973). Moraxella, Acinetobacter and the Mimeae. Bacteriology Reviews 37, 522-545. Hinchliffe, E. & Vivian, A. (1980). Naturally occurring plasmids in Acinetobacter culcoaceticus : a P class factor of restricted host range. Journal of General Microbiology 116, 75-80.
Outbreak
of multi-resistant
A. anitratus
309
Marmur, J. (1961). A procedure for the isolation of DNA from micro-organisms. Journal of Molecular Biology 3, 208-218. Pal, R. B., Sujatha, V. & Kale, V. V. (1981). Acinetobacter calcoaceticus causing subacute bacterial endocarditis. Lancet 2, 393. Retailliau, H. F., Hightower, A. W., Dixon, R. E. & Allen, J. R. (1979). Aciteetobucter calcoaceticus: a nosocomial pathogen with an unusual seasonal pattern. Journal of Infectious Diseases 139, 371-375. Robinson, G. R., Garrison, R. G. & Brown, R. W. (1964). Evaluation of the clinical significance of the genus Herella. Annals of Internal Medicine 60, 19-26. Rudin, M. L., Michael, J. R. & Huxley, E. J. (1979). Community-acquired Acinetobucter pneumonia. American Journal of Medicine 67, 39-42. Taplin, D., Rebell, G. & Zaias, N. (1963). The human skin as a source of Mima-Here&a infections. Journal of the American Medical Association 186, 166-168.
SHORT REPORT
A report of a further hospital outbreak!caused by a multi-resistant Acinetobacter anitratus J. Holton The Middlesex Hospital Medical School, London Wl Introduction
Acinetobacter anitratus has been shown to be the cause of a number of serious infections. There have been reports of it causing endocarditis (Pal, Sujatha and Kale, 1981), meningitis (Ghoneim and Halaka, 1980), pneumonia (Rudin, Michael and Huxley, 1979), and abscesses(Robinson, Garrison and Brown, 1964). It is widely spread in nature being isolated from water, soil and sewage (Henriksen, 1973), and has also been isolated from skin (Taplin, Rebel1 and Zaiaz, 1963). It is a particular risk to debilitated patients and is a recognized hospital-associated pathogen. The epidemiology of hospital outbreaks is not fully understood, although respirometers (Cunha et al., 1980) and humidifiers have been implicated as reservoirs for the organism. Cross-contamination via the hands has been regarded as a possible route of transmission (French et al., 1980). The organism usually shows resistance to ampicillin, cephalothin and chloramphenicol, but is sensitive to the aminoglycosides, sulphonamides, tetracyclines, ureidopenicillins and the third generation cephalosporins (Retailliau et al., 1979; Daschner and Nopper, 1980; Appelbaum et al., 1981). There has been one report of a multi-resistant Acinetobutter spp. causing an outbreak in a urology ward (French et al., 1980). The organism was resistant to 18 antibiotics, being sensitive only to nalidixic acid, colistin, tobramycin and amikacin. A similar outbreak occurred in a surgical intensive care unit (Castle et al., 1978). I report here a further outbreak. Methods and materials
Routine bacteriology specimens were collected over a two-year period (1980-81) and a search made for the typical mucoid, butyrous, domed shaped colonies of A. utitrut2Ls. Suspect colonies were Gram stained and oxidase and motility tests were performed. Full identification was made using API20E. Initial sensitivities were performed by disc diffusion using Stoke’s method. MICs were determined by both the agar dilution method (Oxoid DST agar CM26) using a Steers replicator on all 58 isolates, and on 10 of the isolates by the broth dilution method (Oxoid nutrient broth CMI); an inoculum of 10” cells/ml was used in each case. 0 1982The Hospital Infection Society 0195-6701/82/030305 + 0.5$oz.oo/o 305
J. Holton
306
Soap tolerance was determined using the method of Billings (1965), gelatinase production by the method of Fraser (Cowan and Steel, 1975) and any plasmids were searched for using the technique of Birnboim and Doly (1979) and caesium chloride ultra-centrifugation. The DNA for this latter method was extracted from 100 ml of an overnight culture of acinetobacter by the method of Marmur (1961). Results Over a period of two years there were 58 separate isolates of Acinetobacter spp. Repeat isolates from the same patient were ignored. Most isolates (20) were from sputum, 18 from wound swabs, 14 from urine, five from bile and one from blood culture. Their distribution over the period of study is shown in Figure 1, which reveals a seasonal periodicity, most isolates being found in autumn and winter. Six of the isolates were A. lwoj?I, the remainder were A. anitratus. Of the 52 A. anitratus strains, eight (15 per cent) produced a gelatinase, 35 (67 per cent) grew at 43 “C, all were intolerant of 10 per cent soap and only three isolates grew on 5 per cent soap. A plasmid could not be detected in any of the isolates.
IO 9 P z 0 .2 : =; 5 2
s 7 6 5 4 3 2 1 0 Jan.
Feb. Mm. Apr May
Jam Jul.
Aug.
Sq. Oct. Nov. Dec. Jon. Fab. MO. Apr. May Month
Figure
1. Monthly
distribution
of
Jun. Jul.
Aug
Se,,. Cm.
Nov.
De,
isolation
of isolation
of Acinetobacter strains.
The distribution of MICs demonstrated as ubpopulation that was multiresistant showing resistance to > 256 mg/l of ampicillin, carbenicillin, ticarcillin, mezlocillin, cefoxitin, cefotaxime and gentamicin. These isolates, 34 in number, were also resistant to cefuroxime (> 128 mg/l) and chloramphenicol(64 mg/l) but did not show a bimodal distribution. They were also resistant to trimethoprim, sulphonamide, tetracycline and nitrofurantoin. All isolates were sensitive to nalidixic acid, tobramycin and amikacin. All were soap intolerant, grew at 43 “C and did not produce a gelatinase.
Outbreak
of multi-resistant
A. anitratus
307
The antibiotic resistant organism was isolated from 13 different wards, of which 24/34 (70 per cent) were isolated from five surgical wards and 11/24 of these (46 per cent) on two urological wards. Of the 11 isolates from urological wards, seven were from urine. All of these seven patients had at some time been catheterized. Thirteen isolates occurred on other surgical wards, nine of which were isolated from swabs. Ten were isolated from medical wards, seven of which were from sputa. On the urological wards there were two periods in which the isolates were consecutive. In one instance the same bed was used by two patients, both of whom acquired the multi-resistant organism. Environmental sampling on this ward revealed acinetobacter in the plastic urinals in the sluice, but the bacterium was not found in the ward, bed linen or bed frames. Three of 20 staff carried the acinetobatter on their hands. Sampling of staff on wards not affected demonstrated that two out of 40 carried acinetobacter on their hands, but it was not multiresistant. None of the seven patients had acinetobacter in their faeces and the sampling of 30 faeces from patients on unaffected wards yielded a similar negative result. The patients were isolated, but this did not prevent the appearance of more cases throughout the hospital. The nurses were advised to pay strict attention to handwashing and when changing catheter bags to wear disposable gloves. The plastic urinals were disinfected. After disinfection acinetobacter was not isolated from them. In three cases transfer of patients from infected wards to non-infected wards was associated with further cases in the previously non-infected wards. In two cases patients who were transferred from non-infected wards to infected wards acquired the resistant acinetobacter. A retrospective analysis of nurse and domestic movement could not account for the occurrence throughout the hospital. It was not possible to trace other staff movement in the hospital. After the introduction of strict hygiene measures when touching infected patients or infected materials the epidemic organism was gradually lost from the hospital and has not been re-isolated in the past six months. In this period there have been only three acinetobacter isolates, none of them multi-resistant. Discussion Acinetobacter is an organism normally, although not exclusively, thought of as a nosocomial pathogen affecting debilitated patients. It is usually susceptible to a number of antibiotics. Recently, however, several reports have highlighted multiresistant acinetobacter as an important cause of hospital infection. An organism isolated during the present study seems to be similar to one isolated from another London hospital. It is multi-resistant, grows at 43 “C, is tolerant of soap and does not seem to carry any plasmids to account for the drug resistance. Plasmids have been detected in Acz?zetobacte~spp. and one self-transmissible plasmid has been shown to determine sulphonamide resistance (Hinchliffe and Vivian, 1980). The inability to isolate a plasmid in these particular organisms does not imply the resistance genes are necessarily chromosomally located.
308
J. Holton
With the lack of any effective typing system for Acinetobacter spp. there is no proof that this organism constitutes an epidemic strain even though all the isolates had several factors in common. Further progress in understanding the epidemiology of acinetobacter outbreaks requires the development of a typing system. The outbreak followed a seasonalpattern, an effect which has been noted previously and to which there is no ready explanation. Of the 58 people from which acinetobacter was isolated, 10 people died, and of these the cause of death could be directly attributed to an infection with the organism in three. All these patients were compromised in some way and all died of pneumonia. The source of the organism was not established. It would seem that faeces was not an important reservoir, as it is for other hospital associatedbacteria and that the likely source was the skin of both patients and staff. It is very likely that the plastic urinals were secondarily contaminated. It would seem that movement of patients from ward to ward did spread the strain, but isolation of infected patients did not prevent further casesoccurring in the short term. It is possible that transmission of the organism did occur with movement of staff and the finding of the resistant acinetobacter on the hands of staff would support this. A combination of source isolation and the wearing of gloves when handling infected material prevented further casesfrom occurring. Its role as an opportunist is exemplified by its site of localization. The majority of infections occurred on urology wards and in patients that had been catheterized, although several infections also occurred in wounds on surgical wards and in the lungs of immunocompromised patients. References Appelbaum, P. C., Tamim, J., Stavitz, J. & Aber, R. C. (1981). Sensitivity of Acinetobacter calcoaceticus strains to seven cephalosporins. Lancet ii, 472. Billings, E. (1955). Studies on a soap tolerant organism: a new variety of Bacterium anitratum. Journal of General Microbiology 13, 252-260. Birnboim, H. & Doly, J. (1979). A rapid alkaline extraction procedure for screening recombinant plasmid DNA. Nucleic Acid Research 7, 1513-1523. Castle, M., Tenney, J. H., Weinstein, M. D. & Eickhoff, H. C. (1978). Outbreak of multiply resistant Acinetobacter in a surgical intensive care unit: epidemiology and control. Heart and Lung 7, 641-644. Cowan, S. T. & Steel, K. J. (1975). Manual for the Identification of Medical Bacteria, 2nd edn. Cambridge University Press. Cunha, B. A., Klimek, J. J., Gracewski, J., McLaughlin, J. C. & Quintiliani, R. (1980). A common source outbreak of Acinetobacter pulmonary infections traced to Wright respirometers. Postgraduate Medical Journal 56, 169-173. Daschner, F. & Nopper, S. (1980). Susceptibility of nosocomial Acinetobacter anitratus strains to 14 antibiotics. Journal of Antimicrobial Chemotherapy 6, 415-416. French, G. L., Casewell, M. W., Roncoroni, A. J., Knight, S. & Phillips, I. (1980). A hospital outbreak of antibiotic-resistant Acinetobacter anitratus : epidemiology and control. Journal of Hospital Infection 1, 125-131. Ghoneim, A. T. M. & Halaka, A. (1980). Meningitis due to Acinetobacter calcoaceticus variant anitratus. Journal of Hospital Infection 1, 359-361. Henriksen, S. D. (1973). Moraxella, Acinetobacter and the Mimeae. Bacteriology Reviews 37, 522-545. Hinchliffe, E. & Vivian, A. (1980). Naturally occurring plasmids in Acinetobacter culcoaceticus : a P class factor of restricted host range. Journal of General Microbiology 116, 75-80.
Outbreak
of multi-resistant
A. anitratus
309
Marmur, J. (1961). A procedure for the isolation of DNA from micro-organisms. Journal of Molecular Biology 3, 208-218. Pal, R. B., Sujatha, V. & Kale, V. V. (1981). Acinetobacter calcoaceticus causing subacute bacterial endocarditis. Lancet 2, 393. Retailliau, H. F., Hightower, A. W., Dixon, R. E. & Allen, J. R. (1979). Aciteetobucter calcoaceticus: a nosocomial pathogen with an unusual seasonal pattern. Journal of Infectious Diseases 139, 371-375. Robinson, G. R., Garrison, R. G. & Brown, R. W. (1964). Evaluation of the clinical significance of the genus Herella. Annals of Internal Medicine 60, 19-26. Rudin, M. L., Michael, J. R. & Huxley, E. J. (1979). Community-acquired Acinetobucter pneumonia. American Journal of Medicine 67, 39-42. Taplin, D., Rebell, G. & Zaias, N. (1963). The human skin as a source of Mima-Here&a infections. Journal of the American Medical Association 186, 166-168.