Antimicrobial resistance trends in Shigella serogroups isolated in Israel, 1990-1995.

From a total of 31319 Shigella strains isolated in Israel between 1990 and 1996, 17574 were sent to the National Shigella Reference Center for typing. Of these, 15287 were identified as Shigella sonnei, 1833 as Shigella flexneri, 327 as Shigella boydii and 127 as Shigella dysenteriae. In all, 4395 strains were tested for sensitivity to ampicillin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, nalidixic acid and ofloxacin. All strains tested were sensitive to ofloxacin, and only three strains were resistant to nalidixic acid. Only 113 of 3240 (3.5%) Shigella sonnei strains, 172 of 970 (17.7%) Shigella flexneri strains and 45 of 185 (24.3%) Shigella boydii strains tested were sensitive to four other antibiotic agents. The rates of resistance of Shigella sonnei, Shigella flexneri and Shigella boydii to trimethoprimsulfamethoxazole were 94.4%, 51.3% and 61.6%, respectively. Rates of resistance to ampicillin among these species were 73.4%, 63.5% and 21.4%, respectively. The proportion of strains exhibiting multiple drug resistance was higher for Shigella sonnei than for the other serotypes studied. These results emphasize the need to reassess the use of antibiotic agents in the treatment of shigellosis.