First report of multiresistance gene cfr in Enterococcus species casseliflavus and gallinarum of swine origin

Abstract

The aim of this study was to investigate the presence and genetic environment of the multiresistance gene cfr in Enterococcus species of swine origin. Twenty-five cfr-carrying Enterococcus isolates were collected from swine in Beijing, Guangzhou, and Shandong, China. The isolates consist of 24 Enterococcus casseliflavus and one Enterococcus gallinarum isolate, and exhibited six SmaI PFGE patterns. The cfr gene was located on plasmids in all isolates except E. casseliflavus En83, in which cfr was located on the chromosomal DNA. The cfr gene environments in most of these isolates contain DNA sequences similar to pEF-01, which was first found in Enterococcus. However, inverse PCR analysis suggested that the cfr-carrying circular forms might be different from pEF-01. The circular forms in Eg51 and its transconjugant, and En23, En10, and En94 are similar to the circular form in pEF-01, except for the truncated IS1216, which is replaced by a transposase of the IS256 family in En24. The cfr circular form could not be detected in either En77 or En83, and the same cfr-carrying segments of ∼10 kb had only 3500 bp of sequence similar to pEF-01. This is the first report of cfr gene in E. casseliflavus and E. gallinarum. The potential dissemination of the multidrug resistance gene amongst different bacterial species, especially in enterococci of human and animal origins, is concerning and should be closely monitored.

Introduction

The multiresistance gene cfr encodes a methyltransferase that modifies the C-8 position (Giessing et al., 2009) of A2503 in bacterial 23S rRNA (Kehrenberg et al., 2005) and confers resistance to five chemically unrelated antimicrobial classes, including phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A (Long et al., 2006). It also decreases susceptibility to the 16-membered macrolides spiramycin and josamycin (Smith and Mankin, 2008). Since its initial identification on the multiresistance plasmid pSCFS1 from Staphylococcus sciuri in 2000 (Schwarz et al., 2000), the majority of cfr studies have been conducted in staphylococcal isolates (Shen et al., 2013). It has been found in Staphylococcus lentus, Staphylococcus simulans, Staphylococcus aureus (Kehrenberg and Schwarz, 2006), Staphylococcus hyicus, Staphylococcus warneri (Kehrenberg et al., 2007), Staphylococcus epidermidis (Mendes et al., 2008), Staphylococcus cohnii, Staphylococcus arlettae, Staphylococcus saprophyticus (Wang et al., 2012), Staphylococcus capitis, and Staphylococcus haemolyticus (Cai et al., 2012) from China, Europe, and the United States. However, despite being the second most prevalent leading nosocomial pathogen after Staphylococcus, Enterococcus spp. has rarely been found to carry cfr. The cfr gene has only been reported in two Enterococcus faecalis and two Enterococcus thailandicus isolates from swine or sewage in China, one E. faecalis and one Enterococcus faecium human clinical isolates from Thailand and Canada, respectively (Diaz et al., 2012, Liu et al., 2012b, Liu et al., 2013b, Patel et al., 2013). Under this circumstance, the presence and genetic environment of cfr in Enterococcus isolated from domestic animals in China were investigated in this study.