Escherichia coli isolated from dairy animal feces encoding fosA7.5, conferring resistance to the reserve group antibiotic Fosfomycin

Authors: Haley, Bradd; Kim, Seonwoo; Van Kessel, Jo Ann

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2023
Publication Date: 3/27/2024
Citation: Haley, B.J., Kim, S., Van Kessel, J.S. 2024. Escherichia coli isolated from dairy animal feces encoding fosA7.5, conferring resistance to the reserve group antibiotic Fosfomycin. Foodborne Pathogens and Disease. 10: e0132. https://doi.org/10.1089/fpd.2023.0132.
DOI: https://doi.org/10.1089/fpd.2023.0132

Interpretive Summary: Reserve group antibiotics are “last-resort” antibiotics that should only be used to treat severe or multidrug-resistant infections. Resistance to Fosfomycin, a reserve group antibiotic, is rarely observed in E. coli, but previous analyses of E. coli collected from dairy cows occasionally identified strains encoding fosA7.5, a gene that confers resistance to this antibiotic. To further evaluate the presence of this gene in E. coli collected from cows in the United States, an analysis of fosA7.5-encoding E. coli genomes was conducted. In total, 115 E. coli genomes were identified. Most isolates only encoded the fosA7.5 gene, while 33% encoded at least one other resistance gene, and 25% were multidrug-resistant (MDR). Most strains (93%) were identified as a single lineage known as Phylogenetic Group B1 but there was diversity in this lineage and 19 sequence types (or strain types) were identified. Results of this study show a high level of similarity of fosA-encoding E. coli isolated from cows across a broad geographic area of the United States. These data further our understanding of Fosfomycin resistance in bacteria from dairy production systems and will help scientists further identify and evaluate the potential risk for human exposure to Fosfomycin-resistant bacteria.

Technical Abstract: Dairy animals in the United States are reservoirs of antimicrobial-resistant Escherichia coli that frequently are resistance to tetracyclines, aminoglycosides, B-lactams, sulfonamides, and macrolide-lincosamide-streptogramin B (MLS). However, resistance to other classes of antimicrobials is less frequently observed. Resistance to Fosfomycin, a reserve group antibiotic, is rarely observed in E. coli. Here we describe the genomic characteristics of E. coli encoding the fosA7.5 gene that have been recovered from bovine sources in the United States. Most isolates only encoded the fosA7.5 gene, while 33% encoded at least one other resistance gene, and 25% were genotypically multidrug-resistant. Most strains belonged to phylogenetic group B1 (93%) and were assigned to 19 Sequence Types (STs), the most frequently identified being ST1727, ST2307, and ST3234. Results of this study show a high level of similarity of fosA-encoding E. coli isolated from bovine sources across a wide geographic region of the United States.