Shigella species from Addis Ababa: frequency of isolation and in vitro drug sensitivity.

One hundred and five shigella isolates from Addis Ababa were studied to determine serogroup frequency and in vitro antibacterial drug sensitivity. About 70% of the isolates were Shigella flexneri followed by Sh. dysenteriae (15%), Sh. boydii (10%) and Sh. sonnei (5%). All or most of the strains were susceptible to cephalothin, gentamicin, kanamycin, polymyxin B and trimethoprim-sulphamethoxazole. Frequencies of susceptibility to ampicillin, carbenicillin and chloramphenicol were, respectively, 79, 80 and 75%. Only 37, 23 and 58% were susceptible to streptomycin, sulphadiazine and tetracycline, respectively. Resistance to one or more drugs was detected in 85% while 72% were multiply resistant. There were 24 different resistance patterns, varying from resistance to one drug to resistance to seven drugs. The findings have been compared with reports from other countries. This study and several others cited support the view that trimethoprim-sulphamethoxazole is the best alternative drug for treatment of shigellosis particularly in regions with multiple drug-resistant strains.