title: Decline in macrolide resistance rates among Streptococcus pyogenes causing pharyngitis in children isolated in Italy.
abstract: Macrolides are often used to treat group A streptococcus (GAS) infections, but their resistance rates reached high proportions worldwide. The aim of the present study was to give an update on the characteristics and contemporary prevalence of macrolide-resistant pharyngeal GAS in Central Italy. A total of 592 isolates causing pharyngitis in children were collected in the period 2012-2013. Clonality was assessed by emm typing and pulsed-field gel electrophoresis (PFGE) for all macrolide-resistant strains and for selected susceptible isolates. Genetic determinants of resistance were screened by polymerase chain reaction (PCR). Forty-four GAS were erythromycin-resistant (7.4 %). Among them, 52.3 % and 50 % were clindamycin- and tetracycline-resistant, respectively. erm(B)-positive isolates (52.3 %) expressed the constitutive cMLSB phenotype. mef(A) and its associated M phenotype were recorded in 40.9 % of the cases. The remaining erm(A)-positive isolates expressed the iMLSB phenotype. Seventeen tetracycline-resistant isolates carried tet(M) and five isolates carried tet(O). Twenty-five emm types were found among all strains, with the predominance of emm types 12, 89, 1, and 4. Eleven emm types and 12 PFGE clusters characterized macrolide-resistant strains, with almost two-thirds belonging to emm12, emm4, and emm11. Macrolide-susceptible and -resistant emm types 12, 89, 11, and 4 shared related PFGE profiles. There was a dramatic decline in macrolide resistance in Central Italy among pharyngeal GAS isolates in 2012-2013 when compared to previous studies from the same region (p < 0.05), although macrolide consumption remained stable over the past 15 years. We observed a decrease in the proportion of macrolide-resistant strains within emm types commonly associated with macrolide resistance in the past, namely emm12, 1, and 89.
authors.affiliation: University Campus Bio-Medico, 00128, Roma, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Gherardi
authors.forename: D
authors.initials: D
authors.lastname: Petrelli
authors.forename: M C
authors.initials: MC
authors.lastname: Di Luca
authors.forename: F
authors.initials: F
authors.lastname: Pimentel de Araujo
authors.forename: P
authors.initials: P
authors.lastname: Bernaschi
authors.forename: A
authors.initials: A
authors.lastname: Repetto
authors.forename: J
authors.initials: J
authors.lastname: Bellesi
authors.forename: L A
authors.initials: LA
authors.lastname: Vitali
mesh_terms: D000293:Adolescent; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D002981:Clindamycin / Q000627:therapeutic use*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004917:Erythromycin / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008826:Microbial Sensitivity Tests; D010612:Pharyngitis / Q000188:drug therapy* / Q000382:microbiology; D013290:Streptococcal Infections / Q000188:drug therapy / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D013752:Tetracycline / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D002981:Clindamycin; D004917:Erythromycin; D013752:Tetracycline