Characterization of levofloxacin non-susceptible clinical Streptococcus pyogenes isolated in the central part of Italy

D. Petrelli, M. C. Di Luca, M. Prenna, P. Bernaschi, A. Repetto, L. A. Vitali

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)241-244
Number of pages4
JournalEuropean Journal of Clinical Microbiology and Infectious Diseases
Issue number2
Publication statusPublished - Feb 2014

ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases


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