Decline in macrolide resistance rates among Streptococcus pyogenes causing pharyngitis in children isolated in Italy
European J of Clinical Microb & Inf Diseases SEPT 2015 V.34 N.9 P.1797-1802
- Gherardi, D. Petrelli, M. C. Di Luca…
- University Campus Bio-Medico, 00128, Roma, Italy
- School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
- Department of Microbiology and Infection Control, University Hospital of North Norway, 9038, Tromsø, Norway
- Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
- Unit of Microbiology, Bambino Gesù Children’s Hospital, Roma, Italy
- Azienda Ospedaliera di Perugia, Struttura Complessa di Microbiologia, Santa Maria della Misericordia Hospital Perugia, Perugia, Italy
- Azienda Ospedaliera di Macerata, Macerata, Italy
- School of Pharmacy, Microbiology Unit, University of Camerino, via Gentile III da Varano, 62032, Camerino, MC, Italy
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.
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