Antibiotic resistance pattern of Vibrio cholerae and Shigella causing diarrhoea outbreaks in the eastern Africa region: 1994-1996.

Between March 1994 and December 1996, 1797 rectal swabs were transported to the AMREF laboratory from sites in six countries in the eastern Africa region: 1749 were cultured for Vibrio cholerae and 48 for Shigella/Salmonella. Culture, isolation, identification and antibiotic susceptibility testing were performed using standardized techniques. The isolates were categorized as sensitive or resistant based on standardized zones of inhibition. The rate of isolation of V. cholerae from rectal swabs increased progressively from less than 20% to more than 45% between 1994 and 1996, 80-100% of isolates of V. cholerae from Kenya and south Sudan, and 65-90% from Somalia were sensitive to tetracycline, although in 1995 isolates from Mogadishu showed only 44% sensitivity. All isolates from Tanzania and Rwanda were 100% resistant to tetracycline. In Kenya and Somalia, the percentage of isolates sensitive to chloramphenicol and cotrimoxazole reduced markedly from 85% in 1994 to < 10% in 1996. 100% of isolates from Rwanda and Tanzania were resistant to chloramphenicol and cotrimoxazole while in south Sudan > 70% of isolates were sensitive. Nalidixic acid and erythromycin retained > 75% sensitivity in all areas. Shigella dysenteriae and Shigella flexneri were recovered from dysentery specimens in northern Kenya. Both species showed similar antibiotic sensitivity patterns and were sensitive only to nalidixic acid and furazolidone. Due to variations of resistance patterns within countries in the region, antibiotic sensitivity testing should be performed at the start of an outbreak, and antibiotic use should be restricted to severe cases of V. cholerae and Shigella infection.