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Incidence of Aeromonas species in diarrhoeic stool in University College Hospital Ibadan, Nigeria
Comp. Immun. MicrobioL infect. Dis. Vol. 16, No. 1, pp. 51-54, 1993 Printed in Great Britain. All rights reserved
0147-9571/93 $6.00+0.00 Copyright © 1993 Pergamon Press Ltd
INCIDENCE OF AEROMONAS SPECIES IN DIARRHOEIC STOOL IN UNIVERSITY COLLEGE HOSPITAL IBADAN, NIGERIA J. O. ASHIRU,T. SALAU and I. O. ROTILU Department of Pathology/Microbiology, Faculty of Medical Sciences, The University of West Indies, St Augustine Campus, Trinidad and Tobago, West Indies
(Received for publication 11 August 1992) Abstract--Between February and July 1989, stool samples from 100 diarrhoeic patients were screened for Aeromonas species. For isolation, alkaline peptone water was used for enrichment and xylose desoxycholate citrate agar as differential and selective medium. Only one sample (1%) yielded Aeromonas hydrophila having come from a 2-month old baby. No other enteric pathogens were isolated from the positive stool sample, a strong indication that A. hydrophila was responsible for the diarrhoea in the baby. Of nine antimicrobial agents used the lone A. hydrophila isolate was resistant only to ampicillin. Rbsumr---100 6chantillons des selles des malades diarrheiques ont 6t6 examinrs entre les mois de frvrier et juillet 1989 pour la recherche de microorganismes du genre Aeromonas. Ce microorganisme a 6t6 isol6 en utilisant r eau peptonre alcalinise6 pour l'enrichissement du milieu, et la grlose au xylose desoxycholate cytrate comme milieu differentiel et selectif. Seul l'rchantillon d'un brb6 de deux mois, soit 1%, a 6t6 positif pour Aeromonas hydrophile. Aucun autre microorganisme n'a 6t6, isolr, ce qui plaide en favour du rrle pathogrne d'aeromonase hydrophile. L'antibiogramme utilisant neuf antibiotiques a' 6t6 effectu6 surce microorganism. Celui-ci s'est montr6 rrsistant/t l'ampicilline seule.
INTRODUCTION
Bacterial causes of acute gastroenteritis have long been recognized as a serious problem that occurs in babies between the ages of 6 and 24 months and also in adults [1, 2]. Aeromonas was first isolated from red leg disease in the animals in 1905 by Emerson and Norris [3] and recently the organism was recognized as an enteric pathogen [4]. The incidence of Aeromonas as the causative agents of gastroenteritis in different age groups has been reported by many workers [2, 5-9]. To date, there is only one published report on the isolation of Aeromonas from human gastroenteritis in Nigeria, specifically from Lagos [10]. This study was therefore conducted to assess the incidence of Aeromonas species in human gastroenteritis cases in Ibadan and to evaluate the possible need to routinely screen for this organism while examining stools from diarrhoeic patients. MATERIALS AND METHODS
The stool specimens used in the study were routine specimens sent to the stool bench of the Medical Microbiology Department, of the University College Hospital, Ibadan from patients having been clinically diagnosed as having acute diarrhoea and/or gastroenteritis during a 6 month period between February and July 1989. 51
Aeromonas species in diarrhoeic stool
53
isolated. Salmonella spp was isolated from some patients and this gave an isolation rate of 4%. Three of the Salmonella spp were isolated from babies below 3 yr old while the forth was isolated from an adult. Table 2 gives the result of antibiotic sensitivity test. The isolate of A. hydrophila was found to be sensitive to all the antimicrobial agents used except ampicillin (25 # g) to which it was resistant. DISCUSSION This prospective 6-month study has shown that the incidence of Aeromonas species was comparatively low in relation to the number of stool specimens screened. This low isolation rate detected in this study could be due to geographical factors in different parts of the world earlier documented by Ljungh et al. [13]. The geographical variations in the frequency of isolation of A. hydrophila have been confirmed by Burke et al. [2] with an isolation rate of 10.8% in a population of 975 children in Western Australia only 4% of a study group of 799 children in Britain were positive for the organism [ 14]. The isolation rate of 1% found in this study is in agreement with the report of Agbonlahor[10] on a study also carried out in Nigeria where six strains (0.5%) of A. hydrophila were isolated from 1082 acute gastroenteritis patients in Lagos. Infections by Aeromonas species, are generally believed to be common in immunocompromised host especially infants and geriatric patients. The single isolate in this work was from a baby of 2 months old. The lone strain of A. hydrophila isolated in this study was from a 2-month old baby with no other enteric pathogen detected in the stool sample. This strongly indicates that the isolate was responsible for the diarrhoea in the baby. Agbonlahor [10] also in Lagos, Nigeria isolated A. hydrophila from two infants < 2 yr old. Similarly, Millership et al. [9] reported an isolation rate of 8.1% for A. hydrophila from infants < 1 yr old. Burke et al. [2] also reported the 13 isolates of A. hydrophila from patients below 6 months of age amongst 975 children < 5 yr old sampled. The isolation ofA. hydrophilafrom this baby is in keeping with the decreased immune response typical of infants of this age group. The finding that of nine antimicrobial agents tested the isolate of A. hydrophila was resistant to only ampicillin is in agreement with published work by others [9,10,15]. In fact, it was this characteristic of A. hydrophila that led to the incorporation of ampicillin into blood agar for use as selective and differential media for the isolation of fl-hemolytic Aeromonas species [16]. The fact that Salmonella species were isolated from four (4%) of the stool samples from diarrhoeic patients also suggests that salmonellae may be important as aetiologic agents in human beings in the environment where the patients came. Burke et al. [2] earlier reported an isolation rate of 5.7% for Salmonella from 975 children with diarrhoea in Australia. In conclusion, although the isolation rate of A. hydrophila from faeces of diarrhoeic patients is rather low, the fact that no other pathogen was detected in the baby from whom the isolation was made emphasizes its aetiological significance. There is a need therefore, for a more comprehensive study particularly amongst infants < 6 months old to fully determine the extent of involvement of this agent in diarrhoea. It is only when that is done in the environment that the need to routinely screen stools from diarrhoeic patients in diagnostic laboratories, can be assessed.
54
J.O. ASHIRU et al. REFERENCES
1. Jeukes J., Larson H. E., Price A. B., Saunderson P. G. and Davies H. A. Aetiology of acute diarrhoea in adult gut. 22, 388-392 (1981). 2. Burke V., Gracey M., Robbinson J., Peck D., Beaman J. and Bundell C. The microbiology of childhood gastroenteritis: Aeromonas species and other infective agents J. infect. Dis. 148, 68-74 (1983). 3. Emerson H. and Norris C. Red leg, an infectious disease of frog. J. exp. Med. 7, 32-58 (1905). 4. Lautrop H. Aeromonas hydrophila isolated from human faces and its possible pathological significances. Acta Pathol. Micro. Scand. 144, 299-301 (1961). 5. Altwegg M. and Johl M. Isolation frequencies of Aeromonas species in relation of patient age. Eur. J. clin. Microbiol. 6, 55-56 0987). 6. Champsaur H., Andremont A., Mathieu D., Rottman E. and Auzepy P. Cholera-like illness due to Aeromonas sobria J. infect. Dis. 145, 248-254 (1982). 7. Chatterjee B. D. and Neogy K. N. Studies of Aeromonas and Plesiomonas species isolated from cases of choleraic diarrhoea. Ind. J. reed. Res. 60, 520-524 (1972). 8. Janda J. M., Reitano M. and Bottone E. J. Biotyping of Aeromonas isolates as a correlate to delineating a species associated disease spectrum J. clin. Microbiol. 19, 44-47 (1984). 9. Millership S. E., Curnow S. R. and Chathophy A. Faecal carriage of Aeromonas hydrophila. J. clin. Pathol. 36, 920-923 (1983). 10. Agbonlahor D. E. The role of Aeromonas in acute diarrhoeal disease in Nigeria Central Aft. J. Med. 29, 142 (1983). 1 I. Cowan S. T. and Steel K. J. Identification o f Medical Bacteria, 2nd Edn. Cambridge University Press, Cambridge (1974). 12. Von Graevenitz A. Aeromonas and Plesiomonas in Manual of Clinical Microbiology (Edited by Lennette E. H., Balows A., Howsler W. J. and Shadoney H. J.), 4th Edn, pp. 278-282. American Society of Microbiology, Washington D.C. (1985). 13. Ljungh A., Michael P. and Wadstron T. Aeromonas hydrophila in acute diarrhoea disease, detection of enterotoxin and biotyping of strain. J. din. Microbiol. 6, 90-100 (1977). 14. Price E. H., Hunt G. H., Patel U. and Walker-Smith J. A. Aeromonas spp in diarrhoea. Br. Med. (Clin. Res.) 289, 1380 (1984), 15. Washington J. A. Aeromonas hydrophila in clinical bacteriological specimens. Ann. Int. Med. 76, 611 (1972). 16. Robbinson J., Burke V., Worthy P. J , Beaman J. and Wagener L. Medic for isolation of Aeromonas spp from faeces. J. Med. Microbiol. 18, 405-411 (1984).
0147-9571/93 $6.00+0.00 Copyright © 1993 Pergamon Press Ltd
INCIDENCE OF AEROMONAS SPECIES IN DIARRHOEIC STOOL IN UNIVERSITY COLLEGE HOSPITAL IBADAN, NIGERIA J. O. ASHIRU,T. SALAU and I. O. ROTILU Department of Pathology/Microbiology, Faculty of Medical Sciences, The University of West Indies, St Augustine Campus, Trinidad and Tobago, West Indies
(Received for publication 11 August 1992) Abstract--Between February and July 1989, stool samples from 100 diarrhoeic patients were screened for Aeromonas species. For isolation, alkaline peptone water was used for enrichment and xylose desoxycholate citrate agar as differential and selective medium. Only one sample (1%) yielded Aeromonas hydrophila having come from a 2-month old baby. No other enteric pathogens were isolated from the positive stool sample, a strong indication that A. hydrophila was responsible for the diarrhoea in the baby. Of nine antimicrobial agents used the lone A. hydrophila isolate was resistant only to ampicillin. Rbsumr---100 6chantillons des selles des malades diarrheiques ont 6t6 examinrs entre les mois de frvrier et juillet 1989 pour la recherche de microorganismes du genre Aeromonas. Ce microorganisme a 6t6 isol6 en utilisant r eau peptonre alcalinise6 pour l'enrichissement du milieu, et la grlose au xylose desoxycholate cytrate comme milieu differentiel et selectif. Seul l'rchantillon d'un brb6 de deux mois, soit 1%, a 6t6 positif pour Aeromonas hydrophile. Aucun autre microorganisme n'a 6t6, isolr, ce qui plaide en favour du rrle pathogrne d'aeromonase hydrophile. L'antibiogramme utilisant neuf antibiotiques a' 6t6 effectu6 surce microorganism. Celui-ci s'est montr6 rrsistant/t l'ampicilline seule.
INTRODUCTION
Bacterial causes of acute gastroenteritis have long been recognized as a serious problem that occurs in babies between the ages of 6 and 24 months and also in adults [1, 2]. Aeromonas was first isolated from red leg disease in the animals in 1905 by Emerson and Norris [3] and recently the organism was recognized as an enteric pathogen [4]. The incidence of Aeromonas as the causative agents of gastroenteritis in different age groups has been reported by many workers [2, 5-9]. To date, there is only one published report on the isolation of Aeromonas from human gastroenteritis in Nigeria, specifically from Lagos [10]. This study was therefore conducted to assess the incidence of Aeromonas species in human gastroenteritis cases in Ibadan and to evaluate the possible need to routinely screen for this organism while examining stools from diarrhoeic patients. MATERIALS AND METHODS
The stool specimens used in the study were routine specimens sent to the stool bench of the Medical Microbiology Department, of the University College Hospital, Ibadan from patients having been clinically diagnosed as having acute diarrhoea and/or gastroenteritis during a 6 month period between February and July 1989. 51
Aeromonas species in diarrhoeic stool
53
isolated. Salmonella spp was isolated from some patients and this gave an isolation rate of 4%. Three of the Salmonella spp were isolated from babies below 3 yr old while the forth was isolated from an adult. Table 2 gives the result of antibiotic sensitivity test. The isolate of A. hydrophila was found to be sensitive to all the antimicrobial agents used except ampicillin (25 # g) to which it was resistant. DISCUSSION This prospective 6-month study has shown that the incidence of Aeromonas species was comparatively low in relation to the number of stool specimens screened. This low isolation rate detected in this study could be due to geographical factors in different parts of the world earlier documented by Ljungh et al. [13]. The geographical variations in the frequency of isolation of A. hydrophila have been confirmed by Burke et al. [2] with an isolation rate of 10.8% in a population of 975 children in Western Australia only 4% of a study group of 799 children in Britain were positive for the organism [ 14]. The isolation rate of 1% found in this study is in agreement with the report of Agbonlahor[10] on a study also carried out in Nigeria where six strains (0.5%) of A. hydrophila were isolated from 1082 acute gastroenteritis patients in Lagos. Infections by Aeromonas species, are generally believed to be common in immunocompromised host especially infants and geriatric patients. The single isolate in this work was from a baby of 2 months old. The lone strain of A. hydrophila isolated in this study was from a 2-month old baby with no other enteric pathogen detected in the stool sample. This strongly indicates that the isolate was responsible for the diarrhoea in the baby. Agbonlahor [10] also in Lagos, Nigeria isolated A. hydrophila from two infants < 2 yr old. Similarly, Millership et al. [9] reported an isolation rate of 8.1% for A. hydrophila from infants < 1 yr old. Burke et al. [2] also reported the 13 isolates of A. hydrophila from patients below 6 months of age amongst 975 children < 5 yr old sampled. The isolation ofA. hydrophilafrom this baby is in keeping with the decreased immune response typical of infants of this age group. The finding that of nine antimicrobial agents tested the isolate of A. hydrophila was resistant to only ampicillin is in agreement with published work by others [9,10,15]. In fact, it was this characteristic of A. hydrophila that led to the incorporation of ampicillin into blood agar for use as selective and differential media for the isolation of fl-hemolytic Aeromonas species [16]. The fact that Salmonella species were isolated from four (4%) of the stool samples from diarrhoeic patients also suggests that salmonellae may be important as aetiologic agents in human beings in the environment where the patients came. Burke et al. [2] earlier reported an isolation rate of 5.7% for Salmonella from 975 children with diarrhoea in Australia. In conclusion, although the isolation rate of A. hydrophila from faeces of diarrhoeic patients is rather low, the fact that no other pathogen was detected in the baby from whom the isolation was made emphasizes its aetiological significance. There is a need therefore, for a more comprehensive study particularly amongst infants < 6 months old to fully determine the extent of involvement of this agent in diarrhoea. It is only when that is done in the environment that the need to routinely screen stools from diarrhoeic patients in diagnostic laboratories, can be assessed.
54
J.O. ASHIRU et al. REFERENCES
1. Jeukes J., Larson H. E., Price A. B., Saunderson P. G. and Davies H. A. Aetiology of acute diarrhoea in adult gut. 22, 388-392 (1981). 2. Burke V., Gracey M., Robbinson J., Peck D., Beaman J. and Bundell C. The microbiology of childhood gastroenteritis: Aeromonas species and other infective agents J. infect. Dis. 148, 68-74 (1983). 3. Emerson H. and Norris C. Red leg, an infectious disease of frog. J. exp. Med. 7, 32-58 (1905). 4. Lautrop H. Aeromonas hydrophila isolated from human faces and its possible pathological significances. Acta Pathol. Micro. Scand. 144, 299-301 (1961). 5. Altwegg M. and Johl M. Isolation frequencies of Aeromonas species in relation of patient age. Eur. J. clin. Microbiol. 6, 55-56 0987). 6. Champsaur H., Andremont A., Mathieu D., Rottman E. and Auzepy P. Cholera-like illness due to Aeromonas sobria J. infect. Dis. 145, 248-254 (1982). 7. Chatterjee B. D. and Neogy K. N. Studies of Aeromonas and Plesiomonas species isolated from cases of choleraic diarrhoea. Ind. J. reed. Res. 60, 520-524 (1972). 8. Janda J. M., Reitano M. and Bottone E. J. Biotyping of Aeromonas isolates as a correlate to delineating a species associated disease spectrum J. clin. Microbiol. 19, 44-47 (1984). 9. Millership S. E., Curnow S. R. and Chathophy A. Faecal carriage of Aeromonas hydrophila. J. clin. Pathol. 36, 920-923 (1983). 10. Agbonlahor D. E. The role of Aeromonas in acute diarrhoeal disease in Nigeria Central Aft. J. Med. 29, 142 (1983). 1 I. Cowan S. T. and Steel K. J. Identification o f Medical Bacteria, 2nd Edn. Cambridge University Press, Cambridge (1974). 12. Von Graevenitz A. Aeromonas and Plesiomonas in Manual of Clinical Microbiology (Edited by Lennette E. H., Balows A., Howsler W. J. and Shadoney H. J.), 4th Edn, pp. 278-282. American Society of Microbiology, Washington D.C. (1985). 13. Ljungh A., Michael P. and Wadstron T. Aeromonas hydrophila in acute diarrhoea disease, detection of enterotoxin and biotyping of strain. J. din. Microbiol. 6, 90-100 (1977). 14. Price E. H., Hunt G. H., Patel U. and Walker-Smith J. A. Aeromonas spp in diarrhoea. Br. Med. (Clin. Res.) 289, 1380 (1984), 15. Washington J. A. Aeromonas hydrophila in clinical bacteriological specimens. Ann. Int. Med. 76, 611 (1972). 16. Robbinson J., Burke V., Worthy P. J , Beaman J. and Wagener L. Medic for isolation of Aeromonas spp from faeces. J. Med. Microbiol. 18, 405-411 (1984).