The prevalence and antimicrobial responses of Shigella isolates in HIV-1 infected and uninfected adult diarrhoea patients in north west Ethiopia

Background: Shigella is one of the diarrhoea causing organisms found in HIV positive patients. But so far, the pattern of diarrhoeal agents caused by Shigella in AIDS patients has not been determined. Objective: This study is thus aimed at determining the prevalence, antimicrobial susceptibility and resistance of Shigella isolates in HIV positive subjects. Methods: All stool samples taken from the subjects of this study were plated on the MacConkey agar and incubated at 35-37oC for 24 or 48 hrs. Biochemical and antimicrobial sensitivity testing were carried out by using the standard methods. Results: Out of the 391 subjects included in the study, 199(63.8%) HIV seropositive and 113 seronegative patients had acute and chronic diarrhoea while 79 were HIV seropositive without diarrhoea. Of the 27 (8.7) Shigella isolates taken from the diarrhea patients, 11 (3.5%) were from HIV positive subjects. All Shigella isolates were found to be sensitive against norfloxacin (100%), gentamicin (97%), polymyxin B (97%) and kanamycin (93%). The most frequent resistance observed was to chloramphenicol (62%), tetracycline (86%) and ampicillin (100%). The frequency of resistance of Amp, Sex, Ch, TTc was found to be very high when compared with other patterns of resistance. Conclusion: The high proportion of HIV seropositive patients who had diarrhea in the absence of identified Shigella strains strongly indicates the existence of other diarrhoeagenic agents or mechanisms. Detailed investigation is important to get comprehensive information for better treatment of diarrhoea in HIV /AIDS patients. According to this finding, norfloxacin, gentamicin, polymyxin B, kanamycin and nalidixic acid might be used as drugs of choice for empirical treatment. On the other hand, amplicilin, tetracycline and chloramphenicol may not be used as the drugs of choice for the treatment of Shigella infection unless culture and sensitivity tests are done prior to treatment. The Ethiopian Journal of Health Development Vol. 20 (2) 2006: 99-10