Proteus mirabilis is an opportunistic pathogen associated with a variety of human infections, including urinary tract infections. The prevalence of P. mirabilis in foods of animal origin and in the manure by-products created in animal production is not well documented. Further, the prevalence and persistence of extended-spectrum cephalosporin (ESC) resistant P. mirabilis is largely unknown. In this study, we characterized ESC-resistant P. mirabilis recovered from various stages of dairy manure anaerobic digestion. Isolates were screened by PCR for blaCTX-M, blaCMY and blaSHV, and antimicrobial susceptibility testing was performed. Fifty-six P. mirabilis carrying CTX-M were sequenced with short and long read sequencing technologies, and the assembled chromosomes and plasmids were compared. ESC-resistant Proteus was found in four of the six manure digesters, an indication that not all digesters were colonized with resistant strains. Both CTX-M-1 and CTX-M-15 plasmids were found in P. mirabilis isolates. Transfer of plasmid DNA by conjugation was also explored, with ESC-resistance plasmids able to transfer to Escherichia coli at high frequency. We concluded that P. mirabilis can harbour and transfer ESC-resistance genes and plasmids, and may be an overlooked reservoir of antimicrobial resistance.
Copyright: © 2023 Chalmers et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.