Changing patterns of the prevalence of different Shigella species and their antibiotic susceptibilities in Ankara, Turkey.

Shigella flexneri was the most common Shigella serogroup isolated in Turkey. Recently, an increase in the number of Shigella sonnei isolates was noticed. A retrospective analysis of 2,710 isolates, obtained from stools of Turkish children between January 1980 and September 1994, revealed that, between 1980 and 1987, S. flexneri was the most common subgroup. The isolation rate of S. sonneri increased steadily from 1987 to 1994 reaching to a peak of 78% of all isolates in 1991. The antibiotic susceptibility of 206 strains isolated in 1994 was also studied. A marked difference between the two species was observed for chloramphenicol (98% susceptibility in S. sonnei versus 20% in S. flexneri, ampicillin (90% vs. 18%), ampicillin-sulbactam (98% vs. 53%), and tetracycline (46% vs. 18%) (p < 0.001). Susceptibility to trimethoprim-sulphamethoxazole was similar between the two groups (42% vs. 38%). All isolates were susceptible to ciprofloxacin and ceftriaxone. Comparing our results with resistance rates in 1989, a marked increase in amplicillin (from 44.1% to 82%), chloramphenicol (from 36.7% to 56%) and trimethoprim-sulphamethoxazole (from 35.8% to 62%) resistance was observed.