Antimicrobial susceptibilities of Shigella dysenteriae type 1 isolated in Zimbabwe--implications for the management of dysentery.

Shigella dysenteriae type 1 was cultured from 56/170 (33 pc) rectal swab specimens collected from patients presenting to hospitals in Harare, Zimbabwe with dysentery. All of the isolates were resistant in vitro to trimethoprim-sulfamethoxazole, with MICs > 32 mg/l, and all except one were resistant to ampicillin, most with an MIC > 256 mg/l. One isolate was resistant to nalidixic acid (MIC > 256 mg/l), but all of the others were sensitive, most with an MIC of 2 mg/l or less. Using antibiotic disks, 96 pc isolates were resistant to chloromphenicol and 94 pc to tetracycline. All isolates were sensitive in vitro to gentamicin. On the basis of these findings, we suggest that commonly available antibiotics including ampicillin, cotrimoxazole, chloramphenicol or tetracycline should not be used for the treatment of dysentery. The most appropriate antimicrobial agent at the present time would be nalidixic acid. Resistance to this is, however, likely to emerge and data on susceptibilities to fluoroquinolones as well as to cephalosporins should be obtained so that further recommendations can be given timeously.