title: Evolution of macrolide resistance in Streptococcus pyogenes over 14 years in an area of central Italy.
abstract: We evaluated temporal fluctuations in macrolide resistance rates, analysing genetic determinants of resistance and clonal evolution in a population of 2744 S. pyogenes isolates collected in the period 2000-2013. The total resistance rate to erythromycin of the isolates was 17.9 %. A maximum of erythromycin resistance emerged in 2000 (38.6 %), followed by a significant decrease to 5.2 % in 2012 (P < 0.0001). Molecular analysis revealed the presence and co-presence of known genetic resistance determinants mefA, mefE, ermTR and ermB, in line with phenotypes. PFGE analysis identified genetically related groups in 2000 and 2007-2008, mainly the MLS and M phenotypes, respectively. The most prevalent emm types among a representative subset of resistant isolates were emm2, emm75 and emm77. All emm2 and 88.2 % of the strains harbouring the emm75 gene were only recorded in M-phenotype strains, whilst all emm77-positive strains had the inducible MLS phenotype. The analysed susceptible isolates showed several emm types partially shared with resistant ones. Our results suggest that changes in bacterial population clonality, rather than horizontal transfer of resistance determinants, plays a major epidemiological role in S. pyogenes. Continuous monitoring of microbiological epidemiology seems to be crucial for correct and effective management of streptococcal infections.
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.|Bacteriology Unit, Siena University Hospital, Italy.
authors.forename: Raffaela
authors.initials: R
authors.lastname: Olivieri
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.|University Division of Infectious Diseases, Siena University Hospital, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Morandi
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Zanchi
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.
authors.forename: Giacinta
authors.initials: G
authors.lastname: Tordini
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.|Bacteriology Unit, Siena University Hospital, Italy.
authors.forename: Gianni
authors.initials: G
authors.lastname: Pozzi
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.|University Division of Infectious Diseases, Siena University Hospital, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: De Luca
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.|University Division of Infectious Diseases, Siena University Hospital, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Montagnani
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D005075:Biological Evolution; D002352:Carrier Proteins / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004917:Erythromycin / Q000494:pharmacology; D005798:Genes, Bacterial; D006801:Humans; D007558:Italy / Q000453:epidemiology; D018942:Macrolides / Q000494:pharmacology*; D017720:Molecular Epidemiology; D058889:Molecular Typing; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D015533:Transcriptional Activation; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D018942:Macrolides; C014689:streptococcal M protein; D004917:Erythromycin