Compared with S. aureus RN4220, the transformant carrying pHNLKJC2 had elevated MICs against chloramphenicol (8-fold), florfenicol (16-fold), clindamycin (64-fold), tiamulin (32-fold), valnemulin (32-fold),
and linezolid (4-fold) (Table 1), supporting the presence and the functional activity of cfr. In addition, the transformant carrying pUC18-cfr exhibited 2-fold-elevated MICs for chloramphenicol and florfenicol as compared to E. coli DH5α. Analysis of the genetic environment of cfr in the plasmid pHNTLD18 and pHNLKJC2 JSH-23 molecular weight Southern blotting confirmed that, in Staphylococcus equorum TLD18, cfr was located on a plasmid designed as pHNTLD18. An approximately 5.7-kb EcoRI fragment containing cfr was cloned and sequenced. A Tn558 variant was identified on the plasmid pHNTLD18, in which parts of the Tn558-associated transposase genes tnpA and tnpB were replaced by a cfr-carrying segment and the insertion Selleck ARS-1620 sequence IS21-558 (Figure 1A). Another resistance gene, fexA, encoding an exporter that mediates the active efflux of phenicols, was found to be located downstream of Tn558. Figure 1 Genetic environment of cfr in plasmids pHNTLD18 and pHNLKJC2 and comparison with other similar plasmids. The arrows indicate the positions and directions
of the transcription of the genes. Regions of >98% homology are shaded in grey. Δ indicates a truncated gene. A. genetic environment of cfr in pHNTLD18; B. genetic environment of cfr in pHNLKJC2. The sequences 1,926-bp find more upstream and 2,659-bp downstream of cfr on the plasmid pHNLKJC2 were obtained by primer walking. Basic local alignment search tool (BLAST) analysis of these sequences revealed a 3′-truncated segment of the gene pre/mob upstream of cfr. Further upstream, an incomplete rep gene was detected. Analysis of the region downstream of cfr revealed the presence of a complete pre/mob gene. Immediately downstream of eltoprazine the pre/mob gene, an incomplete macrolide-lincosamide-streptogramin B (MLSB) resistance gene ermC was detected (Figure 1B). Discussion Lack of previous studies on the distribution of the multiresistance gene cfr among staphylococci in retail meat led us to screen 118 meat samples for the same. In our analysis,
cfr was detected in 22 samples. The detection rate was 18.6%, which is higher than the detection rates of food animal samples in China [10, 11]. The low fitness cost of cfr acquisition observed in staphylococcal isolates may account for the persistence of this multiresistance gene in retail meat even in the absence of an antimicrobial selection pressure . The high detection rate found in this study suggested that cfr may be widely disseminated among staphylococci in the meats sold in China, increasing the possibility of this gene entering the food chain. In this study, S. equorum (n = 8) was the predominant species among the 22 cfr-carrying isolates obtained from animal food sources. To the best of our knowledge, this is the first report of cfr in S. equorum. S.