Identification of a novel fosfomycin resistance gene (fosA2) in Enterobacter cloacae from the Salmon River, Canada

Aims: To investigate the occurrence of fosfomycin‐resistant (fos^R) bacteria in aquatic environments. Methods and Results: A fos^R strain of Enterobacter cloacae was isolated from a water sample collected at a site (50°41′33·44″N, 119°19′49·50″W) near the mouth of the Salmon River at Salmon Arm, in south‐central British Columbia, Canada. The strain was identified by PCR screening for plasmid‐borne, fosA‐family amplicons, followed by selective plating. Sequencing of the resistance gene cloned using PCR primers to conserved flanking DNA revealed a new allele (95% amino acid identity to fosA), and I‐Ceu I PFGE showed that it was chromosomally located. In Escherichia coli, the cloned DNA conferred a greater resistance to fosfomycin than its fosA counterpart. Conclusions: Gene fosA2 conferred fosfomycin resistance in an environmental isolate of Ent. cloacae. Significance and Impact of the Study: The repurposing of older antibiotics should be considered in the light of existing reservoirs of resistance genes in the environment.