China Animal Husbandry and Veterinary Medicine ›› 2020, Vol. 47 ›› Issue (1): 229-239.doi: 10.16431/j.cnki.1671-7236.2020.01.027

• Basic Veterinary Medicine • Previous Articles     Next Articles

Main Pathogenic Bacteria Causing Subclinical Mastitis in Yak and the Distribution of Antibiotic Resistance and Virulence Genes

WANG Fei, WANG Cailian, SONG Shuzhen, LANG Xia   

  1. Animal Husbandry-Pasture and Green Agriculture Institute, Gansu Academy of Agricultural Sciences, Lanzhou 730070, China
  • Received:2019-07-19 Online:2020-01-20 Published:2020-01-17

Abstract: To investigate the main pathogenic bacteria causing subclinical mastitis (SCM) in yak and the distribution of antibiotic resistance genes and virulence genes,yak milk samples were collected from the summer pasture in Gannan Tibetan Autonomous Prefecture,Gansu.The Lanzhou mastitis test (CMT) was carried out to grade SCM.16S rDNA was used to identify the main pathogenic bacteria isolated from SCM samples,antibiotic resistance was determined by Kirby-Bauer method,and related antibiotic resistance and virulence genes were detected by PCR.The results showed that a total of 324 SCM samples were found,with the detection rate of 14.43%;The main pathogenic bacteria were Staphylococcus,Escherichia and Enterococcus;Staphylococcus were highly resistant to penicillin and tetracycline with the rate of 59.57% and 47.52% respectively,43.40% and 20.75% E.coli were resistant to tetracycline and ampicillin respectively,as well as 25.00% and 16.67% E.faecalis were resistant to tetracycline and erythromycin respectively;12 strains of methicillin-resistant S.aureus (MRSA) were detected in 59 strains of penicillin-resistant S.aureus,inclouding 7 strains of mecA MRSA and 5 strains of mecC MRSA;For tetracycline-resistant S.aureus,efflux pumps genes tetK and tetA had the highest carrying rate (85.45%,56.36%) and ribosomal protection gene tetM had the lowest frequency (34.55%);Among virulence genes,the detection rates of clfA,clfB,fib and coa genes were higher than others with the ratio of 87.64%,84.27%,83.15%,82.02%,respectively.In conclusion,the main pathogenic bacteria causing SCM in yaks were S.aureus and E.coli which were both highly resistant to penicillins and tetracyclines,and the main virulence factors of S.aureus isolates were clumping factors and coagulase.

Key words: yak; subclinical mastitis (SCM); pathogenic bacteria; antibiotic resistance; antibiotic resistance genes; virulence genes

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