Molecular epidemiology, antimicrobial susceptibilities and resistance mechanisms of Streptococcus pyogenes isolates resistant to erythromycin and tetracycline in Spain (1994–2006)

Virginia Rubio-López,Celia Salcedo,Pilar Villalón,Sylvia Valdezate,María José Medina,Juan-Antonio Sáez-Nieto,David Álvarez

doi:10.1186/1471-2180-12-215

Virginia Rubio-López, Celia Salcedo + Show 5 more

Open Access

https://doi.org/10.1186/1471-2180-12-215

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Abstract

BackgroundGroup A Streptococcus (GAS) causes human diseases ranging in severity from uncomplicated pharyngitis to life-threatening necrotizing fasciitis and shows high rates of macrolide resistance in several countries. Our goal is to identify antimicrobial resistance in Spanish GAS isolates collected between 1994 and 2006 and to determine the molecular epidemiology (emm/T typing and PFGE) and resistance mechanisms of those resistant to erythromycin and tetracycline.ResultsTwo hundred ninety-five out of 898 isolates (32.8%) were erythromycin resistant, with the predominance of emm4T4, emm75T25, and emm28T28, accounting the 67.1% of the 21 emm/T types. Spread of emm4T4, emm75T25 and emm28T28 resistant clones caused high rates of macrolide resistance. The distribution of the phenotypes was M (76.9%), cMLSB (20.3%), iMLSB (2.7%) with the involvement of the erythromycin resistance genes mef(A) (89.5%), msr(D) (81.7%), erm(B) (37.3%) and erm(A) (35.9%).Sixty-one isolates were tetracycline resistant, with the main representation of the emm77T28 among 20 emm/T types. To note, the combination of tet(M) and tet(O) tetracycline resistance genes were similar to tet(M) alone reaching values close to 40%. Resistance to both antibiotics was detected in 19 isolates of 7 emm/T types, being emm11T11 and the cMLSB phenotype the most frequent ones. erm(B) and tet(M) were present in almost all the strains, while erm(A), mef(A), msr(D) and tet(O) appeared in less than half of them.ConclusionsSpanish GAS were highly resistant to macrolides meanwhile showed minor resistance rate to tetracycline. A remarkable correlation between antimicrobial resistance and emm/T type was noticed. Clonal spread of emm4T4, emm75T25 and emm28T28 was the main responsable for macrolide resistance where as that emm77T28 clones were it to tetraclycline resistance. A wide variety of macrolide resistance genes were responsible for three macrolide resistance phenotypes.

Highlights

Group A Streptococcus (GAS) causes human diseases ranging in severity from uncomplicated pharyngitis to life-threatening necrotizing fasciitis and shows high rates of macrolide resistance in several countries
Macrolides and tetracyclines are the most common alternative antibiotics used with penicillin-allergic patients or when first line therapy fails
Increases in macrolide resistance have been reported from many countries, being in Europe, very common in the Mediterranean countries [2,3]

Summary

Introduction

Group A Streptococcus (GAS) causes human diseases ranging in severity from uncomplicated pharyngitis to life-threatening necrotizing fasciitis and shows high rates of macrolide resistance in several countries. A resurgence in serious GAS infections, such as rheumatic fever, and invasive diseases, such as bacteraemia, necrotising fasciitis, septic arthritis, sepsis, pneumonia and streptococcal toxic shock syndrome, has been observed since the mid 1980s. These have become an important cause of morbidity and mortality all over the world [1]. Macrolides and tetracyclines are the most common alternative antibiotics used with penicillin-allergic patients or when first line therapy fails. Increases in macrolide resistance have been reported from many countries, being in Europe, very common in the Mediterranean countries [2,3]

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