Incidence of shigellosis and multi-drug resistant Shigellae: a 10 year study

Between 1976 and 1985 a total of 12,709 faecal samples were cultured. From these samples 760 strains (6.0%) of Shigellae were isolated. Shigella flexneri was the commonest isolate (55%), followed by S. dysenteriae (29.7%). A total of 15.7% of children under 5 years of age were positive for Shigellae. The rate of isolation was lower during the winter months than in the summer months. Only 25 strains (3.3%) were sensitive to all five antibiotics tested. A total of 617 (81.2%) were resistant to three or more antibiotics (multi-drug resistant). The minimum inhibitory concentrations (MICs) of five drugs were calculated in 100 strains. Streptomycin showed an MIC of 25 micrograms ml-1 or less for only seven strains. MICs of chloramphenicol tetracycline and ampicillin were found to be as high as 100-1000 micrograms ml-1 for the majority of strains. Sulphonamide showed an MIC of 1000 micrograms ml-1 for 93 strains.