The detection of fosfomycin resistance genes in Enterobacteriaceae from pets and their owners

The aim of this study was to investigate the prevalence of fosfomycin resistance and molecular characteristic of fosfomycin-resistant strains isolated from companion animals and their owners. A total of 171 samples collected from pets and pet owners in a Chinese veterinary teaching hospital were screened for the presence of phenotype and genotype of fosfomycin-resistance by selective media containing fosfomycin and PCR & sequencing. Among 171 samples tested, nineteen isolates were resistant to fosfomycin. Sixteen and three of these fosfomycin-resistant isolates were positive for fosA3 and fosA genes, respectively. The fosA3 gene was detected both in chromosomes and plasmids in bacteria. All of the fosA3 gene-positive isolates except one were CTX-M producers and nearly half (7/16) of them also harbored the rmtB gene. The fosA3 gene-carrying plasmids, which were readily transferrable to recipient E. coli J53 by conjugation, conferred resistance to multiple antimicrobial agents. Genetic structures were IS26-385bp-fosA3-1810bp-IS26 (n = 11) and IS26-385bp-fosA3-588bp-IS26 (n = 5). Molecular typing indicated that two fosA3-positive isolates from dogs were genetically identical to the isolates from the pet owners. Our results indicated that active transmission of fosA3-mediated fosfomycin resistance has occurred among Enterobacteriaceae isolated from pets and their owners by both horizontal transfer and clonal expansion.