{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T19:24:55Z","timestamp":1779218695973,"version":"3.51.4"},"reference-count":55,"publisher":"Public Library of Science (PLoS)","issue":"6","license":[{"start":{"date-parts":[[2025,6,24]],"date-time":"2025-06-24T00:00:00Z","timestamp":1750723200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100015226","name":"Royal Veterinary College","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100015226","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:p>Antimicrobial resistance is a global threat to both human and animal health, and transfer of resistance between these spheres is recognised as a key concern for all species. Selection for resistance at sub-inhibitory antimicrobial concentrations has been characterised for some bacteria-antimicrobial combinations but there is little data from non-laboratory strains, and veterinary antimicrobials and bacterial species. Here, we demonstrate a minimum selective concentration of 0.06\u2009mg\/L (1\/6 xMIC) for florfenicol in wild-type <jats:italic>Pasteurella multocida<\/jats:italic>, through competition experiments between a susceptible strain and a <jats:italic>floR<\/jats:italic>-resistant mutant. We also show that sub-inhibitory concentrations of florfenicol do not appear to significantly select for <jats:italic>de novo<\/jats:italic> resistance in <jats:italic>P. multocida<\/jats:italic> and present the challenges with adapting experimental protocols between bacterial species. These results have important implications for antimicrobial resistance selection at sub-inhibitory concentrations, method development for within-species differentiation in novel bacterial species, and application to policy regarding antimicrobial contamination in animal-feed.<\/jats:p>","DOI":"10.1371\/journal.pone.0327115","type":"journal-article","created":{"date-parts":[[2025,6,24]],"date-time":"2025-06-24T17:54:11Z","timestamp":1750787651000},"page":"e0327115","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":2,"title":["Selection for florfenicol resistance at sub-MIC concentrations in Pasteurella multocida"],"prefix":"10.1371","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-3641-7070","authenticated-orcid":true,"given":"Abigail","family":"Hughes","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ludovic","family":"Pelligand","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dan I.","family":"Andersson","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3550-3030","authenticated-orcid":true,"given":"Andrew","family":"Mead","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2025,6,24]]},"reference":[{"key":"pone.0327115.ref001","first-page":"1196","article-title":"Veterinary medicine needs new green antimicrobial drugs","volume":"7","author":"P-L Toutain","year":"2016","journal-title":"Front Microbiol"},{"key":"pone.0327115.ref002","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/j.mib.2021.09.009","article-title":"Antimicrobial resistance acquisition via natural transformation: context is everything","volume":"64","author":"M Winter","year":"2021","journal-title":"Curr Opin Microbiol"},{"key":"pone.0327115.ref003","unstructured":"Global Leaders Group on Antimicrobial Resistance. 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Little","year":"2021","journal-title":"Pathogens"},{"issue":"12","key":"pone.0327115.ref041","doi-asserted-by":"crossref","first-page":"2927","DOI":"10.1038\/s41396-019-0483-z","article-title":"Selection for antimicrobial resistance is reduced when embedded in a natural microbial community","volume":"13","author":"U Kl\u00fcmper","year":"2019","journal-title":"ISME J"},{"issue":"4","key":"pone.0327115.ref042","doi-asserted-by":"crossref","DOI":"10.1128\/MMBR.00014-19","article-title":"Pasteurella multocida: genotypes and genomics","volume":"83","author":"Z Peng","year":"2019","journal-title":"Microbiol Mol Biol Rev"},{"issue":"5","key":"pone.0327115.ref043","doi-asserted-by":"crossref","first-page":"519","DOI":"10.1016\/j.femsre.2004.04.001","article-title":"Molecular basis of bacterial resistance to chloramphenicol and florfenicol","volume":"28","author":"S Schwarz","year":"2004","journal-title":"FEMS Microbiol 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Edition","author":"CLSI","year":"2013"},{"issue":"1","key":"pone.0327115.ref047","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1016\/0882-4010(92)90066-W","article-title":"Conditions for transformation of Pasteurella multocida by electroporation","volume":"12","author":"L Jablonski","year":"1992","journal-title":"Microb Pathog"},{"key":"pone.0327115.ref048","doi-asserted-by":"crossref","first-page":"369","DOI":"10.3389\/fcimb.2020.00369","article-title":"Analysis of resistance to florfenicol and the related mechanism of dissemination in different animal-derived bacteria","volume":"10","author":"P Li","year":"2020","journal-title":"Front Cell Infect Microbiol"},{"key":"pone.0327115.ref049","doi-asserted-by":"crossref","first-page":"1787","DOI":"10.3389\/fmicb.2019.01787","article-title":"Diverse mobile genetic elements and conjugal transferability of sulfonamide resistance genes (sul1, sul2, and sul3) in Escherichia coli isolates from Penaeus vannamei and pork from large 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