Laboratory surveillance of Shigella dysenteriae type 1 in KwaZulu-Natal.

OBJECTIVE

To collect data on the antimicrobial susceptibility of Shigella dysenteriae type 1 in KwaZulu-Natal, including the testing of newer therapeutic agents, and to evaluate the ability of laboratories to participate in a provincial surveillance programme.

DESIGN

Prospective descriptive study.

SETTING

Hospital laboratories in KwaZulu-Natal, including peripheral laboratories and the medical microbiology laboratory of the University of Natal.

MAIN OUTCOME MEASURES: Antimicrobial susceptibility pattern of surveillance strains and evaluation of the ability of provincial laboratories to isolate Shigella.

RESULTS

All 354 strains tested were resistant to ampicillin, chloramphenicol and tetracycline. Co-trimoxazole resistance was found in 92.2% of strains, and 0.8% of strains were resistant to nalidixic acid. All strains were susceptible to ceftriaxone, ciprofloxacin, ofloxacin, pivmecillinam, azithromycin, loracarbef and fosfomycin. Of the 29 laboratories surveyed, 18 (62.1%) were able to isolate and identify S. dysenteriae correctly, and 9 (32%) were able to serotype it further to S. dysenteriae type 1. Twenty-seven (93.1%) had appropriate culture media and 26 (89.7%) had antisera for Shigella identification.

CONCLUSIONS

There is little variation among strains of S. dysenteriae type 1 in KwaZulu-Natal with regard to their antimicrobial susceptibility pattern. Nalidixic acid should remain the antimicrobial of choice for treatment of dysentery in our region as resistance to it is low. The majority of KwaZulu-Natal laboratories have the expertise and equipment to perform the isolation and identification of Shigella species.