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Does an Antibiotic Stewardship Applied in a Pig Farm Lead to Low ESBL Prevalence?

ABSTRACT: Background. The aim of the present study was to prospectively evaluate the prevalence of intestinal carriage of colistin-resistant and extended-spectrum β-lactamase (ESBL)-producing Enterobacterales among pigs from a Swiss farm attending an animal health and antibiotic stewardship program and to determine the associated mechanisms of resistance. Materials/Methods. Eighty-one fecal samples were recovered and screened for either β-lactam-resistant, colistin-resistant, or aminoglycoside-resistant Enterobacterales, using respective screening media. All recovered isolates were tested for antimicrobial susceptibility and their clonal relationship (PFGE and MLST). Plasmid typing was performed by plasmid-based replicon typing (PBRT). Resistance genes were searched by PCR and sequencing. Results. A total of 38 ESBL-producing Escherichia coli and a single ESBL-producing Enterobacter cloacae were recovered from 81 pigs, corresponding to a prevalence of 50%, no other β-lactamase producer being identified. Among the 38 ESBL-producing E. coli, all belonged to sequence type (ST) ST10, except two ST34 and ST744 isolates. Among the ST10-bla_CTX-M-1 isolates, three subclones (n = 22, n = 13, and n = 1, respectively) were identified according to the PFGE analysis. The most commonly identified IncI1 plasmid harboring the bla_CTX-M-1 gene was 143 kb in size and coharbored other resistance genes. Only three colistin-resistant Enterobacterales isolates were recovered, namely two Klebsiella pneumoniae isolates and a single E. cloacae isolate. Screening for the plasmid-borne mcr-1 to mcr-9 genes in these three isolates gave negative results. The two K. pneumoniae isolates were clonally related, belonged to ST76, and harbored a truncated mgrB chromosomal gene being the source of colistin resistance. Conclusion. A high prevalence of fecal carriage of ESBL-producing E. coli was found, being mainly caused by the spread of a clonal lineage within the farm. By contrast, a low prevalence of colistin-resistant Enterobacterales was found.

SUBMITTER: Fournier C

PROVIDER: S-EPMC8152456 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Animals are considered important sources of ESBL/AmpC-producing bacteria in humans. We analyzed indications of transfer of ESBL/AmpC genes between pigs and pig farmers in Vietnam by analyzing whole genome sequences of 114 ESBL/AmpC-producing E. coli isolated from the two hosts, and performed conjugation experiments and plasmid profiling to confirm that such transfer could have happened. ESBL-encoding genes detected in pigs and pig farmers included bla CTX-M-55, bla CTX-M-27, bla CTX-M-65, bla CTX-M-15, bla CTX-M-14, bla CTX-M-3, bla CTX-M-24, and bla CARB-2, and AmpC β-lactamases included bla CMY-2, bla DHA-1, and bla CMY-42. The most frequent ESBL gene, bla CTX-M-55, was carried on plasmid with replicons types IncF, IncX, IncH, IncN, IncR, and IncP. The insertion transposases downstream of the bla CTX-M-55 gene were different in plasmids carried by different strains. The second most detected gene, bla CTX-M-27, is found in a stable genetic arrangement with the same flanking transposons seen across strains, and the gene was located on similar conjugal IncF plasmid types, suggesting a horizontal spread of these plasmids. In three strains, we observed a novel bla CTX-M-27 harboring IncF type of plasmid which had not been reported before. Its closest reference in NCBI was the non-ESBL Salmonella Typhimurium plasmid pB71 that might have experienced an insertion of bla CTX-M-27. Our data also point to an emergence of plasmids co-carrying ESBL genes, mcr genes, quinolones and other antimicrobials resistance determinants, and such plasmids require special attention. Plasmids phylogeny confirmed that the bla CTX-M-55 encoding plasmids varied considerably, while those encoding bla CTX-M-27 were closely related. Plasmids harboring both ESBL genes were confirmed to be conjugative and not to differ in transfer efficacy. The isolates carrying the plasmids, even those with plasmids of similar types, showed wide genetic variation with high number of SNPs, suggesting horizontal spread of plasmids into different clonal lines. Their virulence profiles did not confirm to known pathotypes, suggesting that unrelated commensals are a main reservoir for ESBL and AmpC β-lactamases in both humans and pigs. Overall, despite evidence of transferability of plasmids in the analyzed strains, our findings do not support that ESBL-producing E. coli from pigs or their ESBL/AmpC encoding plasmids are commonly spread to workers in close contact with the animals.

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Does an Antibiotic Stewardship Applied in a Pig Farm Lead to Low ESBL Prevalence?

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