Genetic Resistance Elements Carrying mef Subclasses Other than mef (A) in Streptococcus pyogenes

Abstract

In Streptococcus pyogenes, efflux-mediated erythromycin resistance is associated with the mef gene, represented mostly by mef(A), although a small portion of strains carry different mef subclasses. We characterized the composite genetic elements, including mef subclasses other than mef(A), associated with other resistance genes in S. pyogenes isolates. Determination of the genetic elements was performed by PCR mapping. The strains carrying mosaic mef(A/E), in which the 5 region was identical to mef(A) and the 3 region was identical to mef(E), also carried tet(O). The two genes were found enclosed in an element similar to S. pyogenes prophage ⌽m46.1, designated the ⌽m46.1-like element. In S. pyogenes strains carrying mef(E) and tet(M), mef(E) was included in a typical mega element, and in some strains, it was physically associated with tet(M) in the composite element Tn2009. S. pyogenes strains carrying mef(I) also carried catQ; the two genes were linked in a fragment representing a portion of the 5216IQ complex of Streptococcus pneumoniae, designated the defective IQ element. In the only isolate carrying a novel mef gene, this was associated with catQ and tet(M) in a genetic element similar to the 5216IQ complex of S. pneumoniae (5216IQ-like complex), suggesting that the novel mef is in fact a variant of mef(I). This study demonstrates that the composite elements containing mef are shared between S. pyogenes and S. pneumoniae and suggests that it is important to distinguish the mef subclass on the basis of the genetic element containing it.Efflux-mediated macrolide resistance in Streptococcus pyogenes and Streptococcus pneumoniae is conferred by mef and the adjacent msr(D) gene, which code for a two-component transport system (1). The resistance phenotype acquired by the microorganisms is defined as M, since the efflux mechanism confers resistance to macrolides only, as opposed to the MLS B phenotype (resistance to macrolides, lincosamides, and streptogramin B) conferred by the Erm methylase (16).Several allelic variants or subclasses of the mef gene have been described for S. pyogenes and S. pneumoniae, including the more common mef(A) and mef(E) and the rarely encountered mef(I) and mef(O) (3,15,17,20).Although the mef subclasses show a high level of identity at the nucleotide level (from 88% to 94%), each is found embedded in a different genetic element, suggesting a different evolutionary and transmission route (23). In S. pyogenes the most common mef subclass is mef(A) (5, 14), which is carried by two similar genetic elements: Tn1207.3, of approximately 52 kb, and ⌽10394.4, a prophage of approximately 59 kb (2, 21). In S. pneumoniae, mef(A) is carried by Tn1207.1, a defective element of 7.2 kb corresponding to the leftmost mef-containing region of Tn1207.3 (21). In S. pyogenes, a sequence similar to that of Tn1207.1 including mef(A) was found associated with tet(O) in ⌽m46.1, a prophage element of 55.1 kb, also present as a free circular form in the bacterial culture (4).The mef(E) subclass is common in S. ...

Resistance Genes and Genetic Elements Associated with Antibiotic Resistance in Clinical and Commensal Isolates of Streptococcus salivarius

“…Sequencing of the genome of one of these strains revealed that erythromycin [mef(E) gene] and chloramphenicol (catQ gene) resistance determinants colocalized on a genetic element related to the IQ element described for S. pneumoniae (47) and S. pyogenes (42). The IQ F4-20 element is similar to those reported very recently for other viridans group streptococcal species (15) except for the deletion of the 2 ORFs downstream of the left tnp1 gene.…”

“…The macrolide resistance genes erm(A), erm(B), and mef(A/E) and the tetracycline resistance genes tet(M) and tet(O) were detected by PCR amplification using the primers listed in Table S2 in the supplemental material and the con-ditions previously described by Malhotra-Kumar et al (41) for multiplex PCR [except for erm(B) primers, used at 0.8 M instead of 0.5 M]. The chloramphenicol resistance gene catQ was detected as described by Del Grosso et al (42).…”

Tn 5253 Family Integrative and Conjugative Elements Carrying mef (I) and catQ Determinants in Streptococcus pneumoniae and Streptococcus pyogenes

“…By conjugation, while the former defective IQ element proved nontransferable, the latter could be transferred to an S. pyogenes recipient. Apart from its transferability, the latter defective IQ element was quite different from that of the S. pneumoniae 5216IQ complex, since it appeared to be enclosed in a putative genetic element of~50 kb, was located on the opposite side of the Tn5252 fragment, and lacked the Tn916 fragment (6).…”

“…Subsequently, two defective IQ elements were described in Streptococcus pyogenes, one characterized by a considerably shorter region upstream of mef(I) comprising tnp1 and a truncated recombinase gene, rec2, and one reduced to the sole mef(I)-catQ fragment (6). By conjugation, while the former defective IQ element proved nontransferable, the latter could be transferred to an S. pyogenes recipient.…”

ICE Sp1116 , the Genetic Element Responsible for erm (B)-Mediated, Inducible Resistance to Erythromycin in Streptococcus pyogenes

“…The scaffolds are also of various origins and natures. In the case of ICESp1116, the scaffold is related to a streptococcal transposon (TnGallo1); in other cases, it may consist of a Tn916 family transposon (10,22,30), a clostridial ICE (9), or a bacteriophage (1,8,10,20,30).…”