Antimicrobial resistance trends of shigellae isolates from Calabar, Nigeria

During a 3-year study (January 1986-December 1988), stools of 2200 diarrhoeal or dysenteric patients were examined by culturing and 108 (4.9%) were found positive for shigellae. Shigella flexneri was the commonest species isolated (54.6%), followed by Sh. dysenteriae (24.1%). Patients aged less than or equal to 15 years accounted for 51.4% of cases. Shigellae over the 3 years showed high and sometimes rising resistance to ampicillin, chloramphenicol, streptomycin and cotrimoxazole and complete resistance to tetracyclines and sulphonamides. Sh. sonnei strains isolated in 1986 and 1987 were almost invariably sensitive to all antimicrobial agents except ampicillin, while in 1988 strains were resistant to all. The isolation rate was higher (74.1%) during the dry season than in the rainy season (25.9%) (P less than 0.01). Low standards of community and personal hygiene and improper sewage disposal are the prevailing epidemiological factors identified.