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 flexn eri, 327 as Shigella boydii and 127 as Shigella dysenteriae. In all, 4395 s trains were tested for sensitivity to ampicillin, trimethoprim-sulfamethoxa zole, tetracycline, chloramphenicol, nalidixic acid and ofloxacin. All stra ins tested were sensitive to ofloxacin, and only three strains were resista nt 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 boy dii strains tested were sensitive to four other antibiotic agents. The rate s of resistance of Shigella sonnei, Shigella flexneri and Shigella boydii t o trimethoprim-sulfamethoxazole 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 re sistance was higher for Shigella sonnei than for the other serotypes studie d. These results emphasize the need to reassess the use of antibiotic agent s in the treatment of shigellosis.