Molecular characterisation of quinolone-resistant Shigella strains isolated in Tehran, Iran.

Over the past few years, the number of Shigella strains resistant to nalidixic acid has increased and has made the selection of effective antimicrobial therapy more difficult. The purpose of this study was to investigate the molecular mechanism of quinolone resistance in Shigella strains. Shigella strains isolated from 1100 diarrhoeal patients in Tehran, Iran, were assessed for their susceptibility to nalidixic acid prior to PCR-RFLP and sequence analysis of their quinolone resistance genes. Among 73 Shigella strains isolated, 23 (31.5%) were resistant to nalidixic acid. The most common Shigella spp. was Shigella sonnei (54; 74.0%). Of the 23 quinolone-resistant isolates, 4 (17.4%) (includi…