Multiple Antibiotic Resistance Gene Transfer from Animal to Human Enterococci in the Digestive Tract of Gnotobiotic Mice

It has been proposed that food animals represent the source of glycopeptide resistance genes present in enterococci from humans. We demonstrated the transfer of vanA and of other resistance genes from porcine to human Enterococcus faecium at high frequency in the digestive tract of gnotobiotic mice. Tylosin in the drinking water favored colonization by transconjugants

Update on linezolid resistance in staphylococci

National audienceLinezolid is the only oxazolidinone antibiotic approved for clinical use. It inhibits bacterial protein synthesis by an original mechanism blocking the initiation phase, at a very early stage. It binds to the ribosome at the domain V of 23S rRNA and prevents transfer of amino acid on tRNA from A-site to P-site. Linezolid resistance was reported quickly after its marketing 10 years ago in clinical isolates of staphylococci and though it has progressed with the use of linezolid it remains rare (less than 1%). The three mechanisms of linezolid resistance described in staphylococci so far involve the 50S ribosomal subunit. This resistance is mainly associated with a variety of mutations in the genes encoding either 23S rRNA or exceptionally ribosomal proteins. The most common target site mutation observed clinically is the G2576 T. Recently, a new mechanism has been described by acquisition of the cfr gene. This gene, that methyls the adenine in position 2503 of domain V, is carried by plasmids that can promote the dissemination of linezolid resistance. Linezolid resistance could be detected by phenotypic methods according to usual standard procedures and confirmed by in-house genotypic methods. (C) 2012 Elsevier Masson SAS. All rights reserved

Inhibitory impact of bifidobacteria on the transfer of beta-lactam resistance among Enterobacteriaceae in the gnotobiotic mouse digestive tract

While looking for new means to limit the dissemination of antibiotic resistance, we evaluated the role of potentially probiotic bifidobacteria on the transfer of resistance genes between enterobacteria. Transfers of bla genes encoding extended-spectrum β-lactamases (SHV-5 and CTX-M-15) were studied in the absence or presence of bifidobacteria. In vitro, transfer frequencies of these bla genes decreased significantly in the presence of three of five tested strains, i.e., Bifidobacterium longum CUETM-89-215, Bifidobacterium bifidum CIP-56.7T, and Bifidobacterium pseudocatenulatum CIP-104168T. Four transfer experiments were conducted in the digestive tract of gnotobiotic mice, the first three observing the effect of B. longum CUETM-89-215, B. bifidum CIP-56.7T, and B. pseudocatenulatum CIP-104168T on bla(SHV-5) transfer and the fourth experiment studying the effect of B. bifidum CIP-56.7T on bla(CTX-M-15) transfer. These experiments revealed significant decreases in the transconjugant levels (up to 3 logs) in mice having received B. bifidum CIP-56.7T or B. pseudocatenulatum CIP-104168T compared to control mice. Bifidobacteria appear to have an inhibitory impact on the transfer of antibiotic resistance genes. The inhibitory effect is associated to specific bifidobacterial strains and may be related to the production of thermostable metabolites by these strains