{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,15]],"date-time":"2026-07-15T14:44:06Z","timestamp":1784126646157,"version":"3.55.0"},"reference-count":44,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,7,25]],"date-time":"2025-07-25T00:00:00Z","timestamp":1753401600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Vet. Sci."],"abstract":"<jats:sec><jats:title>Introduction<\/jats:title><jats:p>Antimicrobial resistance (AMR) poses significant challenges to health and treatment options in both human and veterinary medicine. Animal AMR monitoring in the US evaluates carcasses, retail meat, live animals, and diagnostic laboratory submissions; however, there is a lack of consistent on-farm monitoring of use and resistance.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>In 2020, 153 pig farms in the Midwestern United States enrolled in an antimicrobial purchase and resistance monitoring program. Intestinal samples or fecal swabs were collected biannually for 3\u202fyears from pigs and their dunging areas; antibiotic purchase data were tracked. <jats:italic>Salmonella enterica<\/jats:italic> and <jats:italic>Escherichia coli<\/jats:italic> were isolated and underwent antibiotic susceptibility testing using either a commercial bovine\/ porcine (BOPO 7F) panel (for pig samples) or the National Antimicrobial Resistance Monitoring System (NARMS) Gram-negative panel (for dunging area samples). Minimum inhibitory concentrations (MICs) of antibiotics were used to evaluate the susceptibility of pig sample isolates, while NARMS breakpoints were used to assess resistance in isolates from dunging areas.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Tetracyclines were the most purchased, and penicillins were the most used antibiotic class across farm types. For pig samples, more isolates exhibited MIC values at the high end of the tested range among <jats:italic>E. coli<\/jats:italic> and <jats:italic>Salmonella<\/jats:italic> isolates from wean-to-market (WTM) sites compared to breed-to-wean (BTW) sites for almost all antibiotic classes. In addition, <jats:italic>E. coli<\/jats:italic> isolates from sick pigs had higher MIC values compared to isolates from substandard but otherwise healthy pigs. Among the dunging area isolates, both bacteria had higher rates of resistance in the WTM sites compared to the BTW sites across multiple antibiotics.<\/jats:p><\/jats:sec><jats:sec><jats:title>Discussion<\/jats:title><jats:p>Individual ages of pigs were a likely confounder and were not controlled for, as these data were not reliably collected. A greater frequency of monitoring, along with controlling for age, recent treatments, and disease events at the individual level, would improve farm-level insights from on-farm AMR monitoring. Currently, the interpretation of phenotypic AMR data for resistance monitoring in swine medicine is limited by the lack of established veterinary breakpoints for enteric organisms. The available NARMS breakpoints are designed for humans, can be used for public health monitoring, and are likely to be applicable primarily to gastrointestinal infections involving the same bacteria in farm animals.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fvets.2025.1586008","type":"journal-article","created":{"date-parts":[[2025,7,25]],"date-time":"2025-07-25T11:32:52Z","timestamp":1753443172000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":3,"title":["Assessment of a program for monitoring antimicrobial purchase and resistance in Escherichia coli and Salmonella enterica on pig farms in the Midwestern United States from May 2020 through October 2023"],"prefix":"10.3389","volume":"12","author":[{"given":"Karyn A.","family":"Havas","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roy","family":"Edler","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laura","family":"Ruesch","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marlee","family":"Braun","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter","family":"Ferm","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Noelle R.","family":"Noyes","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laura B.","family":"Goodman","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"H. Morgan","family":"Scott","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joel","family":"Nerem","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taylor","family":"Spronk","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Scott A.","family":"Dee","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2025,7,25]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"100561","DOI":"10.1016\/j.lana.2023.100561","article-title":"The burden of antimicrobial resistance in the Americas in 2019: a cross-country systematic analysis","volume":"25","author":"Aguilar","year":"2023","journal-title":"Lancet Regional Health - Americas"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"629","DOI":"10.1016\/S0140-6736(21)02724-0","article-title":"Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis","volume":"399","author":"Murray","year":"2022","journal-title":"Lancet"},{"key":"ref3","year":"2020"},{"key":"ref4","doi-asserted-by":"publisher","first-page":"e02693","DOI":"10.1128\/mBio.02693-18","article-title":"One health genomic surveillance of Escherichia coli demonstrates distinct lineages and Mobile genetic elements in isolates from humans versus livestock","volume":"10","author":"Ludden","year":"2019","journal-title":"MBio"},{"key":"ref5","doi-asserted-by":"publisher","first-page":"20140085","DOI":"10.1098\/rstb.2014.0085","article-title":"The livestock reservoir for antimicrobial resistance: a personal view on changing patterns of risks, effects of interventions and the way forward","volume":"370","author":"Aarestrup","year":"2015","journal-title":"Philos Trans R Soc B"},{"key":"ref6","doi-asserted-by":"publisher","first-page":"1616","DOI":"10.3390\/antibiotics12111616","article-title":"Antimicrobial resistance in commensal Escherichia coli of the porcine gastrointestinal tract","volume":"12","author":"O\u2019Neill","year":"2023","journal-title":"Antibiotics"},{"key":"ref7","doi-asserted-by":"publisher","first-page":"428","DOI":"10.1046\/j.1365-2672.2003.01988.x","article-title":"Transfer of antibiotic resistance between commensal and pathogenic members of the Enterobacteriaceae under ileal conditions","volume":"95","author":"Blake","year":"2003","journal-title":"J Appl Microbiol"},{"key":"ref8","year":"2020"},{"key":"ref9","year":"2012"},{"key":"ref10","year":"2021"},{"key":"ref11","doi-asserted-by":"publisher","first-page":"545","DOI":"10.1089\/fpd.2017.2283","article-title":"National Antimicrobial Resistance Monitoring System: two decades of advancing public health through integrated surveillance of antimicrobial resistance","volume":"14","author":"Karp","year":"2017","journal-title":"Foodborne Pathog Dis"},{"key":"ref12","doi-asserted-by":"publisher","first-page":"109006","DOI":"10.1016\/j.vetmic.2021.109006","article-title":"Genomics accurately predicts antimicrobial resistance in Staphylococcus pseudintermedius collected as part of vet-LIRN resistance monitoring","volume":"254","author":"Tyson","year":"2021","journal-title":"Vet Microbiol"},{"key":"ref13","year":"2023"},{"key":"ref14","year":"2020"},{"key":"ref15","doi-asserted-by":"publisher","first-page":"106","DOI":"10.54846\/jshap\/1002","article-title":"Antimicrobial susceptibility of Actinobacillus pleuropneumoniae, Pasteurella multocida, Streptococcus suis, and Bordetella bronchiseptica isolated from pigs in the United States and Canada, 2011 to 2015","volume":"25","author":"Sweeney","year":"2017","journal-title":"JSHAP"},{"key":"ref16","doi-asserted-by":"publisher","first-page":"130","DOI":"10.54846\/jshap\/1282","article-title":"Antimicrobial susceptibility of Actinobacillus pleuropneumoniae, Bordetella bronchiseptica, Pasteurella multocida, and Streptococcus suis isolated from diseased pigs in the United States and Canada, 2016 to 2020","volume":"30","author":"Sweeney","year":"2022","journal-title":"JSHAP"},{"key":"ref17","year":"2024"},{"key":"ref18","year":"2024"},{"key":"ref19","volume-title":"AVMA guidelines for the euthanasia of animals: 2020 edition","author":"Leary","year":"2020"},{"key":"ref20","doi-asserted-by":"publisher","first-page":"758","DOI":"10.1126\/science.103.2687.758","article-title":"A useful selective bactericidal property of Tergitol-7","volume":"103","author":"Pollard","year":"1946","journal-title":"Science"},{"key":"ref21","first-page":"504","article-title":"A superior culture medium for the enumeration and differentiation of coliforms","volume":"53","author":"Chapman","year":"1947","journal-title":"J Bacteriol"},{"key":"ref22","volume-title":"Media fo isolation-cultivation-identification-maintenance of medical Bacteria","author":"MacFaddin","year":"1985"},{"key":"ref23","year":"2024"},{"key":"ref24","year":"2019"},{"key":"ref25","year":"2021"},{"key":"ref26","doi-asserted-by":"publisher","first-page":"e00190-20","DOI":"10.1128\/mSystems.00190-20","article-title":"Bactopia: a flexible pipeline for complete analysis of bacterial genomes","volume":"5","author":"Petit","year":"2020","journal-title":"mSystems"},{"key":"ref27","doi-asserted-by":"publisher","first-page":"e00483-19","DOI":"10.1128\/AAC.00483-19","article-title":"Validating the AMRFinder tool and resistance gene database by using antimicrobial resistance genotype-phenotype correlations in a collection of isolates","volume":"63","author":"Feldgarden","year":"2019","journal-title":"Antimicrob Agents Chemother"},{"key":"ref28","volume-title":"Performance standards for antimicrobial susceptibility testing. [CLSI M100]","year":"2024"},{"key":"ref29","first-page":"160","article-title":"Antimicrobial resistance of fecal Escherichia coli isolated from grow-finish pigs in 20 herds in Alberta and Saskatchewan","volume":"72","author":"Rosengren","year":"2008","journal-title":"Can J Vet Res"},{"key":"ref30","doi-asserted-by":"publisher","first-page":"6","DOI":"10.1111\/zph.12760","article-title":"Antimicrobial use in wean to market pigs in the United States assessed via voluntary sharing of proprietary data","volume":"67","author":"Davies","year":"2020","journal-title":"Zoonoses Public Health"},{"key":"ref31","volume-title":"Performance standards for antimicrobial disk and dilution susceptibility tests for bacteria isolated from animals. [CLSI supplement VET01S]","year":"2024"},{"key":"ref32","doi-asserted-by":"publisher","first-page":"179","DOI":"10.1016\/j.prevetmed.2015.02.008","article-title":"Effects of chlortetracycline and copper supplementation on the prevalence, distribution, and quantity of antimicrobial resistance genes in the fecal metagenome of weaned pigs","volume":"119","author":"Agga","year":"2015","journal-title":"Prev Vet Med"},{"key":"ref33","doi-asserted-by":"publisher","first-page":"622495","DOI":"10.3389\/fvets.2020.622495","article-title":"Age dependence of antimicrobial resistance among fecal Bacteria in animals: a scoping review","volume":"7","author":"Gaire","year":"2021","journal-title":"Front Vet Sci"},{"key":"ref34","doi-asserted-by":"publisher","first-page":"184","DOI":"10.1186\/s12866-015-0512-7","article-title":"Longitudinal study of the early-life fecal and nasal microbiotas of the domestic pig","volume":"15","author":"Slifierz","year":"2015","journal-title":"BMC Microbiol"},{"key":"ref35","year":"2022"},{"key":"ref36","doi-asserted-by":"publisher","first-page":"52","DOI":"10.20506\/rst.42.3348","article-title":"Antimicrobial use and antimicrobial resistance monitoring in pig production in the United States of America: -EN- antimicrobial use and antimicrobial resistance monitoring in pig production in the United States of America -FR- La surveillance de l\u2019utilisation des agents antimicrobiens et de l\u2019antibior\u00e9sistance dans la production porcine aux \u00c9tats-unis d\u2019Am\u00e9rique -ES- Vigilancia del uso de agentes antimicrobianos y de la Resistencia a ellos en la producci\u00f3n porcina de los Estados Unidos de Am\u00e9rica","volume":"42","author":"Spronk","year":"2023","journal-title":"Rev Sci Tech OIE"},{"key":"ref37","doi-asserted-by":"publisher","first-page":"501","DOI":"10.2460\/ajvr.68.5.501","article-title":"Changes in antimicrobial susceptibility in a population of Escherichia coli isolated from feedlot cattle administered ceftiofur crystalline-free acid","volume":"68","author":"Lowrance","year":"2007","journal-title":"Am J Vet Res"},{"key":"ref38","doi-asserted-by":"publisher","first-page":"540","DOI":"10.3389\/fvets.2020.00540","article-title":"Monitoring of farm-level antimicrobial use to guide stewardship: overview of existing systems and analysis of key components and processes","volume":"7","author":"Sanders","year":"2020","journal-title":"Front Vet Sci"},{"key":"ref39","doi-asserted-by":"publisher","first-page":"1","DOI":"10.2460\/ajvr.23.05.0086","article-title":"Benefits and challenges of creating veterinary antibiograms for empiric antimicrobial selection in support of antimicrobial stewardship and advancement of one-health goals","author":"Burbick","year":"2023","journal-title":"AJVR"},{"key":"ref40","doi-asserted-by":"publisher","first-page":"6.2.08","DOI":"10.1128\/microbiolspec.ARBA-0001-2017","article-title":"Antimicrobial susceptibility testing of Bacteria of veterinary origin","volume":"6","author":"Watts","year":"2018","journal-title":"Microbiol Spectr"},{"key":"ref41","doi-asserted-by":"publisher","first-page":"418","DOI":"10.1111\/j.1469-0691.2006.01377.x","article-title":"Statistical characterisation of bacterial wild-type MIC value distributions and the determination of epidemiological cut-off values","volume":"12","author":"Turnidge","year":"2006","journal-title":"Clin Microbiol Infect"},{"key":"ref42","year":"2021"},{"key":"ref43","doi-asserted-by":"publisher","first-page":"2344","DOI":"10.3389\/fmicb.2017.02344","article-title":"En route towards European clinical breakpoints for veterinary antimicrobial susceptibility testing: a position paper explaining the VetCAST approach","volume":"8","author":"Toutain","year":"2017","journal-title":"Front Microbiol"},{"key":"ref44","year":"2023"}],"container-title":["Frontiers in Veterinary Science"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fvets.2025.1586008\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,7,25]],"date-time":"2025-07-25T11:32:53Z","timestamp":1753443173000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fvets.2025.1586008\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,7,25]]},"references-count":44,"alternative-id":["10.3389\/fvets.2025.1586008"],"URL":"https:\/\/doi.org\/10.3389\/fvets.2025.1586008","relation":{},"ISSN":["2297-1769"],"issn-type":[{"value":"2297-1769","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,7,25]]},"article-number":"1586008"}}