Isolation,identification,and drug resistance characteristics analysis of Staphylococci from dairy cow mastitis in the Yunnan Region
Xie Xiaodong
Cao Rongchang
Cheng Zhentao
Liu Xiaoxing
Ma Fengli
Wang Tao
Abstract：This study aimed to elucidate the epidemiological characteristics and antibiotic resistance patterns of Staphylococcus species isolated from dairy cow mastitis in Yunnan Province.A total of 30 milk samples were collected from cows with clinical mastitis on local large-scale dairy farms.Bacterial isolation and identification were performed based on colony morphology,Gram staining,biochemical tests,and 16S rRNA gene sequencing.Antibiotic susceptibility of the isolates to 20 antimicrobial agents was determined using the Kirby-Bauer disk diffusion method,and the presence of 10 resistance genes was detected by PCR.The results showed that four Staphylococcus strains were isolated and identified as Staphylococcus chromogenes(PT-1 and PT-2),Staphylococcus aureus(PT-3),and Staphylococcus cohnii(PT-4)via 16S rRNA analysis.The genetic homology among the isolates ranged from 96.3%to 100.0%,indicating close phylogenetic relationships with local reference strains from Yunnan.Phylogenetic analysis revealed that the isolates clustered with some Yunnan strains in the same branch but were separated into distinct branches from most reference strains both domestically and internationally,suggesting regional evolutionary adaptation.The isolates exhibited notable antibiotic resistance,showing sensitivity to cephalosporins,polymyxin B,and ciprofloxacin but reduced susceptibility to commonly used clinical antibiotics such as penicillins and macrolides.All strains carried the β-lactam resistance gene blaTEM-1(carriage rate:100%).Notably,PT-1 also harbored the aadA1(aminoglycoside resistance)and tetA(tetracycline resistance)genes,demonstrating multidrug resistance.The study indicates that the blaTEM-1 gene serves as a core resistance marker in Staphylococcus isolates from dairy cow mastitis in Yunnan.To enhance prevention and control efficacy,clinical management of bovine mastitis should integrate antibiotic susceptibility testing with genetic detection results to develop precise treatment strategies.
Keywords：MastitisBacteriaStaphylococcusDrug resistance geneDairy cow
Publication Date：2026-01-15
Online Publishing Date：2026-03-05(First online date of this platform, not the publication date of the document)
Pages：7( 69-75 )