title: Characterization of levofloxacin non-susceptible clinical Streptococcus pyogenes isolated in the central part of Italy.
abstract: We investigated the prevalence, genetics, and clonality of fluoroquinolone non-susceptible isolates of Streptococcus pyogenes in the central part of Italy. S. pyogenes strains (n = 197) were isolated during 2012 from patients with tonsillopharyngitis, skin, wound or invasive infections and screened for fluoroquinolone non-susceptibility (resistance to norfloxacin and levofloxacin minimum inhibitory concentration (MIC) = 2 mg/L) following EUCAST guidelines. First-step topoisomerase parC and gyrA substitutions were investigated using sequencing analysis. Clonality was determined by pulsed field gel electrophoresis (PFGE; SmaI digestion) and by emm typing. The fluoroquinolone non-susceptible phenotype was identified in 18 isolates (9.1 %) and correlated with mutations in parC, but not in gyrA, the most frequent leading to substitution of the serine at position 79 with an alanine. Most of the fluoroquinolone non-susceptible isolates belonged to the emm-type 6, even if other emm-types were also represented (emm75, emm89, and emm2). A significant level of association was measured between PFGE and both emm type and substitutions in parC. The prevalence of fluoroquinolone non-susceptible Streptococcus pyogenes isolates in Italy is of concern and, although the well-known emm type 6 is dominant, other types are appearing and spreading.
authors.affiliation: School of Biosciences and Biotechnology, University of Camerino, Camerino, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Petrelli
authors.forename: M C
authors.initials: MC
authors.lastname: Di Luca
authors.forename: M
authors.initials: M
authors.lastname: Prenna
authors.forename: P
authors.initials: P
authors.lastname: Bernaschi
authors.forename: A
authors.initials: A
authors.lastname: Repetto
authors.forename: L A
authors.initials: LA
authors.lastname: Vitali
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D007223:Infant; D007558:Italy / Q000453:epidemiology; D064704:Levofloxacin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D058889:Molecular Typing; D015995:Prevalence; D017422:Sequence Analysis, DNA; D013290:Streptococcal Infections / Q000453:epidemiology*; D013297:Streptococcus pyogenes / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D064704:Levofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase