title: Molecular characterisation of quinolone-resistant Shigella strains isolated in Tehran, Iran.
abstract: 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%) (including 2 Shigella flexneri, 1 S. sonnei and 1 Shigella boydii) contained the qnrS gene. However, none of the isolates harboured qnrA or qnrB genes. PCR-RFLP analysis of gyrA showed a mutation profile in two nalidixic acid-resistant strains, including one S. sonnei and one S. flexneri. Sequencing of mutant gyrA genes revealed a point mutation at position 83, resulting in the replacement of serine by leucine. In conclusion, molecular mechanisms of resistance to quinolones were identified in 6 of 23 Shigella isolates. Other possible mechanisms of resistance should also be investigated for better characterisation of quinolone-resistant Shigella isolates.
authors.affiliation: Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. Electronic address: ranjbarre@gmail.com.
authors.forename: Reza
authors.initials: R
authors.lastname: Ranjbar
authors.affiliation: Department of Microbiology, Islamic Azad University, Damghan Branch, Damghan, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Behnood
authors.affiliation: Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Hamed
authors.initials: H
authors.lastname: Memariani
authors.affiliation: Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Najafi
authors.affiliation: Department of Microbiology, Islamic Azad University, Damghan Branch, Damghan, Iran.
authors.forename: Majid
authors.initials: M
authors.lastname: Moghbeli
authors.affiliation: Department of Sciences for Health Promotion and Mother-Child Care 'G. D'Alessandro', University of Palermo, Palermo, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Mammina
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004405:Dysentery, Bacillary; D005798:Genes, Bacterial; D006801:Humans; D007492:Iran; D008826:Microbial Sensitivity Tests; D015363:Quinolones / Q000494:pharmacology*; D012760:Shigella / Q000187:drug effects* / Q000235:genetics; D012764:Shigella sonnei
chemical_list: D000900:Anti-Bacterial Agents; D015363:Quinolones; D027081:DNA Gyrase
keywords: Mutation; Nalidixic acid; Quinolone resistance; Shigella; gyrA