Escherichia coli Isolated from Bovine Sources Encoding the Fosfomycin Resistance Gene fosA7.5

Dairy animals are reservoirs of antimicrobial-resistant Escherichia coli that are frequently resistant to tetracycline, aminoglycoside, β-lactam, sulfonamide, and macrolide-lincosamide-streptogramin B antibiotics. However, resistance to other classes of antimicrobials is less frequently observed, and resistance to fosfomycin is rarely observed in E. coli. In this study, we describe the genomic characteristics of E. coli encoding fosA7.5 that have been recovered from bovine sources in the United States. Most isolates only encoded the fosA7.5 gene, whereas 37% encoded at least one other resistance gene, and 25% were genotypically multidrug-resistant. Most (112 isolates, 93%) belonged to phylogenetic group B1 and were assigned to 19 sequence types (STs), the most frequently identified being ST1727, ST2307, and ST3234. Results of this study indicate that fosA-encoding E. coli from bovine sources is very rare in the United States with isolates demonstrating a high level of similarity across a broad geographic region.