{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T15:58:56Z","timestamp":1785427136252,"version":"3.56.0"},"reference-count":35,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T00:00:00Z","timestamp":1778198400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["31772795"],"award-info":[{"award-number":["31772795"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"award":["31772795"],"award-info":[{"award-number":["31772795"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>Antimicrobial resistance (AMR) in Escherichia coli (E. coli) from food-producing animals constitutes a substantial public health concern. This study characterized antimicrobial resistance profiles, phylogenetic diversity, virulence-gene distribution, and plasmid-borne extended-spectrum \u03b2-lactamase (ESBL) determinants of E. coli isolates recovered from water buffaloes with subclinical mastitis. Among the 54 ESBL-producing E. coli isolates, all were resistant to ampicillin and cefotaxime. High resistance rates were also observed for cephalothin (75.9%), trimethoprim\u2013sulfamethoxazole (74.0%), ceftiofur (70.4%), florfenicol (68.5%), and cefazolin (63.0%). Lower resistance was recorded for colistin sulfate (40.7%), enrofloxacin (33.3%), and gentamicin (25.9%). Phylogenetic analysis of ESBL producers identified phylogroup B1 (42.6%) as predominant, followed by groups A (29.6%) and D (25.9%). Multilocus sequence typing (MLST) revealed that ST50 (20.4%) was the most common sequence type, and serogroup O150 was dominant (70.4%). Virulence genes, such as iss (81.5%), astA (59.3%), and espP (38.9%), were frequently detected among ESBL isolates. ESBL genes were predominantly blaCTX-M-1 (27.8%) in all isolates, while the narrow-spectrum \u03b2-lactamase genes blaTEM-1 (55.6%) and blaOXA-10 (14.8%) were also commonly co-detected. Bioinformatic analysis predicted that all ESBL genes were associated with plasmid-derived contigs, with the predicted plasmid size ranging from approximately 32 to 187 kb and belonging to IncFIB, IncFIA, IncI1, IncFIA + I1, and IncFII replicon types. Conjugation frequencies ranged from 4.8 \u00d7 10\u22127 to 4.1 \u00d7 10\u22122, and plasmids were predicted to carry additional resistance genes mediating resistance to chloramphenicol (floR), sulfonamides (sul1, sul3), tetracyclines (tet(A) and tet(B)), and trimethoprim (dfrA1, dfrA12). The co-carriage of ESBL genes with additional antimicrobial resistance and virulence determinants suggests the potential role of water buffaloes as reservoirs of clinically relevant resistance traits that may disseminate through horizontal gene transfer.<\/jats:p>","DOI":"10.3390\/microorganisms14051055","type":"journal-article","created":{"date-parts":[[2026,5,11]],"date-time":"2026-05-11T20:14:16Z","timestamp":1778530456000},"page":"1055","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Antimicrobial Susceptibility and Characterization of Extended-Spectrum \u03b2-Lactamases in Escherichia coli Isolated from Buffalo Mastitis Milk in Guangdong Province, China"],"prefix":"10.3390","volume":"14","author":[{"given":"Yunchen","family":"Zhou","sequence":"first","affiliation":[{"name":"School of Animal Science and Technology, Foshan University, Foshan 528231, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rong","family":"Xi","sequence":"additional","affiliation":[{"name":"School of Animal Science and Technology, Foshan University, Foshan 528231, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Siran","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Animal Science and Technology, Foshan University, Foshan 528231, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ban","family":"Li","sequence":"additional","affiliation":[{"name":"School of Animal Science and Technology, Foshan University, Foshan 528231, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yue","family":"Wu","sequence":"additional","affiliation":[{"name":"School of Animal Science and Technology, Foshan University, Foshan 528231, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chengbo","family":"Wen","sequence":"additional","affiliation":[{"name":"School of Animal Science and Technology, Foshan University, Foshan 528231, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1758-3524","authenticated-orcid":false,"given":"Dexian","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Animal Science and Technology, Foshan University, Foshan 528231, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,8]]},"reference":[{"key":"ref_1","unstructured":"O\u2019Neill, J. (2025, November 24). Review on Antimicrobial Resistance: Tackling Drug-Resistant Infections Globally: Final Report and Recommendations, Available online: https:\/\/apo.org.au\/node\/63983."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1016\/j.vetmic.2018.03.013","article-title":"Antimicrobial usage and presence of extended-spectrum \u03b2-lactamase-producing Enterobacteriaceae in animal-rearing households of selected rural and Peri-Urban Communities","volume":"218","author":"Okpara","year":"2018","journal-title":"Vet. Microbiol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"161","DOI":"10.1016\/S1473-3099(15)00424-7","article-title":"Emergence of plasmid-mediated colistin resistance mechanism mcr-1 in animals and human Beings in China: A microbiological and molecular biological study","volume":"16","author":"Liu","year":"2016","journal-title":"Lancet Infect. Dis."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1450","DOI":"10.1038\/s41564-019-0445-2","article-title":"Emergence of plasmid-mediated high-level tigecycline resistance genes in animals and humans","volume":"4","author":"He","year":"2019","journal-title":"Nat. Microbiol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1457","DOI":"10.1038\/s41564-019-0496-4","article-title":"Plasmid-encoded tet (X) genes that confer high-level tigecycline resistance in Escherichia coli","volume":"4","author":"Sun","year":"2019","journal-title":"Nat. Microbiol."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Liu, Z.H., Wang, K., Zhang, Y.R., Xia, L., Zhao, L., Guo, C., Liu, X., Qin, L., and Hao, Z. (2022). High prevalence and diversity characteristics of blaNDM, mcr, and blaESBL harboring multidrug-resistant Escherichia coli from chicken, pig, and cattle in China. Front. Cell. Infect. Microbiol., 11.","DOI":"10.3389\/fcimb.2021.755545"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/bs.aambs.2020.03.001","article-title":"Antimicrobial resistance genes in bacteria from animal-based foods","volume":"112","author":"Ferrari","year":"2020","journal-title":"Adv. Appl. Microbiol."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Liu, H.H., Wang, Y.L., Wang, G., Xing, Q.T., Shao, L.H., Dong, X.M., Sai, L.T., Liu, Y.J., and Ma, L.X. (2015). The prevalence of Escherichia coli strains with extended spectrum beta-lactamases isolated in China. Front. Microbiol., 6.","DOI":"10.3389\/fmicb.2015.00335"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Cantas, L., Suer, K., Guler, E., and Imir, T. (2015). High emergence of ESBL-producing E. coli cystitis: Time to get smarter in Cyprus. Front. Microbiol., 6.","DOI":"10.3389\/fmicb.2015.01446"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1099\/jmm.0.036806-0","article-title":"Detection of clinically important beta-lactamases in commensal Escherichia coli of human and swine origin in western China","volume":"61","author":"Tian","year":"2012","journal-title":"J. Med. Microbiol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.vetmic.2012.03.009","article-title":"Prevalence of ESBL and PMQR genes in fecal Escherichia coli isolated from the non-human primates in six zoos in China","volume":"159","author":"Wang","year":"2012","journal-title":"Vet. Microbiol."},{"key":"ref_12","first-page":"86","article-title":"Virulence factors of Escherichia coli isolated from recurrent cases of clinical and subclinical mastitis in buffaloes","volume":"4","author":"Lamey","year":"2013","journal-title":"Int. J. Microbiol. Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"e443","DOI":"10.1016\/S2666-5247(22)00037-4","article-title":"Gut colonisation by extended-spectrum \u03b2-lactamase-producing Escherichia coli and its association with the gut microbiome and metabolome in Dutch adults: A matched case-control study","volume":"3","author":"Ducarmon","year":"2022","journal-title":"Lancet Microbe"},{"key":"ref_14","unstructured":"Adkins, P.R.F., and Middleton, J.R. (2017). Laboratory Handbook on Bovine Mastitis, National Mastitis Council."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Zhang, D., Lu, X., Feng, X., Shang, X., Liu, Q., Zhang, N., and Yang, H. (2023). Molecular characteristics of Staphylococcus aureus strains isolated from subclinical mastitis of water buffaloes in Guangdong Province, China. Front. Vet. Sci., 10.","DOI":"10.3389\/fvets.2023.1177302"},{"key":"ref_16","unstructured":"CLSI (2017). Performance Standards for Antimicrobial Susceptibility Testing, Clinical Laboratory Standards Institute (CLSI). CLSI Document M100-S27."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"524","DOI":"10.1186\/s13059-014-0524-x","article-title":"The Harvest suite for rapid core-genome alignment and visualization of thousands of intraspecific microbial genomes","volume":"15","author":"Treangen","year":"2014","journal-title":"Genome Biol."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Liu, H.X., Zhou, H.C., Li, Q.F., Peng, Q., Zhao, Q., Wang, J., and Liu, X. (2018). Molecular characteristics of extended-spectrum \u03b2-lactamase-producing Escherichia coli isolated from the rivers and lakes in Northeast China. BMC Microbiol., 18.","DOI":"10.1186\/s12866-018-1270-0"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"521","DOI":"10.1051\/vetres:2003023","article-title":"Severity of E. coli mastitis is mainly determined by cow factors","volume":"34","author":"Burvenich","year":"2003","journal-title":"Vet. Res."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"491","DOI":"10.1007\/s11250-015-0973-6","article-title":"Prevalence of contagious and environmental mastitis-causing bacteria in bulk tank milk and its relationships with milking practices of dairy cattle herds in Sao Miguel Island (Azores)","volume":"48","author":"Azevedo","year":"2016","journal-title":"Trop. Anim. Health Prod."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1186\/1751-0147-43-221","article-title":"Occurrence of clinical and sub-clinical mastitis in dairy herds in the West Littoral Region of Uruguay","volume":"43","author":"Gianneechini","year":"2002","journal-title":"Acta Vet. Scand."},{"key":"ref_22","first-page":"265","article-title":"Isolation and identification of bacterial flora from subclinical mastitic buffaloes in Hyderabad District, Sindh, Pakistan","volume":"33","author":"Memon","year":"2013","journal-title":"Pak. Vet. J."},{"key":"ref_23","first-page":"1202","article-title":"Prevalence and antimicrobial resistance of major pathogens isolated from bovine mastitis in northern China","volume":"14","author":"Wang","year":"2015","journal-title":"J. Dairy Sci."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"11704","DOI":"10.1038\/s41598-025-95914-x","article-title":"Emergence of highly virulent multidrug and extensively drug resistant Escherichia coli and Klebsiella pneumoniae in buffalo subclinical mastitis cases","volume":"15","author":"Chowdhury","year":"2025","journal-title":"Sci. Rep."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Penati, M., Musa, L., Pavesi, L.F., Guaraglia, A., Ulloa, F., Moroni, P., Piccinini, R., and Addis, M.F. (2024). Multidrug-resistant extended-spectrum beta-lactamase (ESBL)-Producing Escherichia coli in a dairy herd: Distribution and antimicrobial resistance profiles. Antibiotics, 13.","DOI":"10.20944\/preprints202402.0156.v1"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Ali, T., Rahman, S.U., Zhang, L., Shahid, M., Zhang, S., Liu, G., Gao, J., and Han, B. (2016). ESBL-producing Escherichia coli from cows suffering mastitis in China contain clinical class 1 integrons with CTX-M linked to ISCR1. Front. Microbiol., 7.","DOI":"10.3389\/fmicb.2016.01931"},{"key":"ref_27","first-page":"1248","article-title":"Prevalence of subclinical mastitis and antibiogram of Escherichia coli in cow milk of Western Chitwan","volume":"10","author":"Aavash","year":"2023","journal-title":"J. Vet. Med. Res."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2322541","DOI":"10.1080\/10495398.2024.2322541","article-title":"Prevalence and molecular characterization of multi-resistant Escherichia coli isolates from clinical bovine mastitis in China","volume":"35","author":"Zhao","year":"2024","journal-title":"Anim. Biotechnol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1303","DOI":"10.1007\/s42770-023-00955-x","article-title":"Occurrence of extended-spectrum beta-lactamase-producing Enteobacteriaceae in raw milk from cows with subclinical mastitis in northeast Brazil","volume":"54","author":"Sierra","year":"2023","journal-title":"Braz. J. Microbiol."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Anueyiagu, K.N., Agusi, E.R., Kabantiyok, D., Ayanbimpe, G.M., and Ikeh, E.I. (2025). Zoonotic potential of ESBL-producing coliforms in pastorally managed ruminants with subclinical mastitis in Plateau State, Nigeria. Front. Antibiot., 4.","DOI":"10.3389\/frabi.2025.1632264"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2631","DOI":"10.1002\/vms3.942","article-title":"Antibiogram and virulence profiling reveals multidrug resistant Staphylococcus aureus as the predominant aetiology of subclinical mastitis in riverine buffaloes","volume":"8","author":"Hoque","year":"2022","journal-title":"Vet. Med. Sci."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"852","DOI":"10.3168\/jds.2019-17320","article-title":"Short communication: Bovine mastitis caused by a multidrug-resistant, mcr-1-positive (colistin-resistant), extended-spectrum \u03b2-lactamase-producing Escherichia coli clone on a Greek dairy farm","volume":"103","author":"Filioussis","year":"2020","journal-title":"J. Dairy Sci."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Ribeiro, L.F., Nespolo, N.M., Rossi, G.A.M., and Fairbrother, J.M. (2024). Exploring extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in food-producing animals and animal-derived foods. Pathogens, 13.","DOI":"10.3390\/pathogens13040346"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"lxae058","DOI":"10.1093\/jambio\/lxae058","article-title":"Prevalence and characteristics of ESBL-producing Escherichia coli in clinically healthy pigs: Implications for antibiotic resistance spread in livestock","volume":"135","author":"Oliveira","year":"2024","journal-title":"J. Appl. Microbiol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1016\/j.vetmic.2016.08.010","article-title":"Detection of plasmid-borne extended-spectrum \u03b2-lactamase (ESBL) genes in Escherichia coli isolates from bovine mastitis","volume":"200","author":"Freitag","year":"2017","journal-title":"Vet. Microbiol."}],"container-title":["Microorganisms"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2607\/14\/5\/1055\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,11]],"date-time":"2026-05-11T20:28:27Z","timestamp":1778531307000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2607\/14\/5\/1055"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,8]]},"references-count":35,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2026,5]]}},"alternative-id":["microorganisms14051055"],"URL":"https:\/\/doi.org\/10.3390\/microorganisms14051055","relation":{},"ISSN":["2076-2607"],"issn-type":[{"value":"2076-2607","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,8]]}}}