Abstract
The multi-resistance gene cfr is widely distributed among various gram-positive and gram-negative species in livestock in China. To better understand the epidemiology of cfr among Staphylococcus spp. and E. coli isolates, 254 Staphylococcus spp. and 398 E. coli strains collected from six swine farms in China were subjected to prevalence and genetic analysis. Forty (15.7%) Staphylococcus spp. isolates, including 38 Staphylococcus sciuri strains, one Staphylococcus chromogenes strain, and one Staphylococcus lentus strain, and two (0.5%) E. coli isolates were found to contain the cfr gene. Most of the 38 S. sciuri strains were clonally unrelated; however, clonal dissemination of cfr-positive S. sciuri was detected at the same farm. In eight randomly selected cfr-positive staphylococci, a cfr-harboring module (IS21-558-cfr-ΔtnpB) was detected in six S. sciuri isolates; cfr was bracketed by two copies of ISEnfa4 or IS256 in the remaining two S. sciuri isolates. In the two E. coli isolates, EP25 and EP28, cfr was flanked by two IS26 elements in the same or opposite orientation, respectively. Complete sequence analysis of the novel F43:A-:B- plasmid pHNEP28 revealed that it contains two multi-resistance regions: cfr together with floR, qnrS1 interspersed with IS26, ΔISCR2 and ISKpn19, and blaTEM-1 together with tet(M) interspersed with IS26, ISApl1, ΔTn2, and ΔIS1B. The coexistence of cfr with other resistance genes on a conjugative plasmid may contribute to the dissemination of these genes by co-selection. Thus, rational drug use and continued surveillance of cfr in swine farms are warranted.
Highlights
The multi-resistance gene cfr encodes a methyltransferase that modifies position A2503 at 23S rRNA and confers resistance to six different classes of antibiotics that bind to the peptidyl transferase center (Kehrenberg et al, 2005; Giessing et al, 2009)
Cfr was detected in 40 (15.7%) Staphylococcus spp. and two (0.5%) E. coli isolates
Farm GDEP in the Guangdong province showed the highest prevalence of cfr-positive (37.5%) Staphylococcus spp. strains and it was the only farm with cfr-positive E. coli strains (Table 1)
Summary
The multi-resistance gene cfr encodes a methyltransferase that modifies position A2503 at 23S rRNA and confers resistance to six different classes of antibiotics that bind to the peptidyl transferase center (Kehrenberg et al, 2005; Giessing et al, 2009). Cfr confers resistance to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A antibiotics (the PhLOPSA phenotype) and reduces susceptibility to the 16-membered macrolides josamysin cfr in Staphylococci and Escherichia coli from Pigs and spiramycin (Long et al, 2006), which are used extensively in the treatment of infections in both humans and animals. The cfr gene was first identified in a bovine Staphylococcus sciuri isolate (Stefan et al, 2000) and subsequently in staphylococcal isolates of human and animal origin from around the world (Shen et al, 2013). Various Enterococcus, Bacillus, Macrococcus, Jeotgalicoccus, Streptococcus suis, Proteus vulgaris, and Escherichia coli strains have been reported to be cfr-positive (Shen et al, 2013; Wang et al, 2013b). The cfr gene is widely disseminated in staphylococci from pigs in China (Shen et al, 2013), and increasingly reported in porcine E. coli isolates in China. We identified cfrpositive Staphylococcus spp. and E. coli isolates from the same farm and determined the complete nucleotide sequence of a novel conjugative F43:A-:B- plasmid bearing cfr in an E. coli isolate
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