JAC Advance Access published online on January 23, 2006
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dki490
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1 Department of Medical Microbiology, University of Aberdeen School of Medicine, Polwarth Buildings, Foresterhill, Aberdeen AB25 2ZD, UK
* To whom correspondence should be addressed. Objectives: To study the molecular mechanisms of erythromycin resistance in Methods: Erythromycin-resistant clinical isolates from North East Scotland were collected over 2 years. Resistance phenotypes were determined by disc diffusion and MICs by Etest. Resistance genes mef, msr(D), erm(B) and erm(TR) were identified by PCR and mef and msr(D) were sequenced. Results: Erythromycin resistance prevalence was 1.9% in group A streptococci (31 of 1625), 4.3% in group B (53 of 1233), 3.8% in group C (18 of 479) and 6.2% in group G (64 of 1034). The numbers of resistant isolates available were 26, 42, 9 and 52 in each group respectively. The majority of resistant isolates in groups A (57.7%, 15 of 26), B (88.1%, 37 of 42) and G (90.4%, 47 of 52) were MLSB. The contribution of M phenotype was significant in groups C (77.8%, 7 of 9) and A (42.3%, 11 of 26). Group A isolates carried mef(A) and group B carried mef(E) exclusively. A mef sequence distinct from mef(A) and mef(E) was identified in group G and was associated with a new msr(D) sequence. These sequence variants appear to be part of a new genetic element that is inserted in the comEC gene. A bimodal distribution of erythromycin MICs was noted in erm(TR) isolates. Conclusions: The results demonstrate significant differences in the mechanisms of macrolide resistance amongst different Lancefield groups in the same geographical area. New sequences show that resistance mechanisms are still evolving.
Received September 1, 2005
Revised December 16, 2005
Accepted December 20, 2005
Original article
Molecular epidemiology of macrolide resistance in
Maria Rosario Amezaga 1
and
Hamish McKenzie 1 *
-haemolytic streptococci of Lancefield groups A, B, C and G and evidence for a new mef element in group G streptococci that carries allelic variants of mef and msr(D)
Hamish McKenzie, E-mail: h.mckenzie{at}abdn.ac.uk
Abstract 
-haemolytic streptococci of Lancefield groups A, B, C and G.
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