Antibiotic resistance of prevalent Salmonella and Shigella strains in northwest Ethiopia.

Salmonella and Shigella strains were isolated prospectively from in- and outpatient specimens of the Gondar College teaching hospital over a two year period, from June 1994 to May 1996. Of 7993 miscellaneous specimens cultured, 80 yielded Salmonella and 147 Shigella. Serogroup B dominated among the salmonella, accounting for 61% of isolates, followed by S. typhi (21%). S. flexneri (58.5%) and S. dysenteriae (36.7%) were the most frequently isolated species among the Shigella. Results of sensitivity testing to five commonly used antibiotics in the area: ampicillin, chloramphenicol, gentamicin, tetracycline and cotrimoxazole, showed multiple drug resistance among the isolates of both salmonella and shigella. Only 4% of shigella were sensitive to all five antibiotics screened for in the study. Overall sensitive of shigella isolates to individual antibiotics was 8.8% to tetracycline, 10% to ampicillin, 28% to co-trimoxazole and 98% to gentamicin. No resistance was observed to nalidixic acid among 108 shigella strains tested for this antibiotic. The continued sensitivity of S. typhi to chloramphenicol, cotrimoxazole, ampicillin and the other commonly used antibiotics is noted. It is recommended that nalidixic acid be introduced into the area under strict regulation for treatment of severe cases of shigella dysentery, an illness which is highly endemic in the region and the cause of occasional epidemics with high mortality.