Identification and characterisation of fosfomycin resistance in Escherichia coli urinary tract infection isolates from Australia

Of 1033 Escherichia coli urinary tract infection isolates collected from females >12 years of age in Australia in 2019, only 2 isolates were resistant to fosfomycin with a minimum inhibitory concentration (MIC) of >256 mg/L. Despite having different multilocus sequence types, the two isolates harboured an identical plasmid-encoded fosA4 gene. The fosA4 gene has previously been identified in a single clinical E. coli isolate cultured in Japan in 2014. Each fosfomycin-resistant isolate harboured two conjugative plasmids that possessed an array of genes conferring resistance to aminoglycosides, β-lactams, macrolides, quinolones, sulfonamides and/or trimethoprim.