Presence of family phage-like elements conferring efflux-mediated macrolide resistance in group G streptococci
Abstract number: 1732_133
Figueiredo T.A., Pinho M.D., Melo-Cristino J., Ramirez M.
Objectives: Recently, we demonstrated that the prophage-like elements belonging to the Tn1207.3/Phi10394.4 family in Streptococcus pyogenes encode a DNA-modifying methyltransferase. In this study, the presence of the Tn1207.3/Phi10394.4 family was evaluated in group G streptococci (GGS) presenting the M phenotype.
Methods: Five GGS clinical isolates identified as Streptococcus dysgalactiae ssp. equisimilis and expressing the M phenotype of macrolide resistance were collected from 2002 to 2005 in Portugal. The presence of the mef gene as well as it linkage with the msr(D) gene, both involved in macrolide resistance, were investigated by PCR. The isolates were also characterised by PFGE. To identify the general structure of the mef genetic elements, the presence of phage-related ORFs belonging to the Tn1207.3/Phi10394.4 family was investigated by PCR, including the one encoding M.Spy10394I. Moreover, to discriminate between these two genetic elements, the structure of the left insertion site in the bacterial chromosome and a Phi10394.4-specific ORF, annotated as encoding an R28-like protein were investigated.
Results: The analysis of SmaI PFGE patterns showed that three of the isolates were clonally related while one was not typable by PFGE, since its DNA was resistant to SmaI digestion. All isolates showed the presence and linkage of mef and msr(D) genes and four carried the mef(E) variant while only one carried the mef(A) variant. Only the isolate, refractory to SmaI digestion and positive for the mef(A) variant, was also positive for all PCR reactions performed. The structure of the left insertion site of the Tn1207.3/Phi10394.4 family in the chromosome of this isolate revealed that in this streptococcal species the elements are inserted at the same locus as in S. pyogenes. Moreover, the absence of a PCR product for the ORF encoding the R28-like protein established Tn1207.3 as the element present in this strain.
Conclusion: The data demonstrated the presence of an element of the Tn1207.3/Phi10394.4 family in a GGS isolate. Resistance to SmaI digestion in this M phenotype isolate is probably due to the expression of the M.Spy10394I methylase, previously described in S. pyogenes. The dissemination of the Tn1207.3/Phi10394.4 family among S. pyogenes and GGS emphasize the important role of these related chimeric elements and their associated prophage in the worldwide emergence of macrolide resistant streptococci expressing the M phenotype.
|Session name:||European Society of Clinical Microbiology and Infectious Diseases|
|Location:||ICC, Munich, Germany|
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