Decline in macrolide resistance rates among Streptococcus pyogenes causing pharyngitis in children isolated in Italy

September 6, 2015 at 6:55 pm

European J of Clinical Microb & Inf Diseases SEPT 2015 V.34 N.9 P.1797-1802

  1. Gherardi, D. Petrelli, M. C. Di Luca…
  2. University Campus Bio-Medico, 00128, Roma, Italy
  3. School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
  4. Department of Microbiology and Infection Control, University Hospital of North Norway, 9038, Tromsø, Norway
  5. Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
  6. Unit of Microbiology, Bambino Gesù Children’s Hospital, Roma, Italy
  7. Azienda Ospedaliera di Perugia, Struttura Complessa di Microbiologia, Santa Maria della Misericordia Hospital Perugia, Perugia, Italy
  8. Azienda Ospedaliera di Macerata, Macerata, Italy
  9. 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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Entry filed under: Antimicrobianos, Bacterias, Biología Molecular, Epidemiología, Infecciones oro-faríngeas, Metodos diagnosticos, Resistencia bacteriana.

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