Preliminary Study On Escherichia Coli From Bovine Subclinical Mastitis In Part Of Xingjiang

Occurrence of bovine subclinical mastitis in dairy farms in part of Xinjiang was investigated with methods of epidemiology, microbiology and molecularbiology. Preliminary researches on antibiotic susceptibility, immunogenicity, and protein structure of E.coli isolated from Bovine subclinical mastitis were made.Subclinical mastitis infection rate and infection of mammary quarters were 63.93% and 31.76%, respectively and isolation rate of E.coli from milk samples and mammary quarters were 29.64% and 11.86%, respectively in 8 dairy farms. Drug susceptibility testing shown that the drug susceptibility of E.coli's isolated from different farm was similar. All of E. coli isolated from different herds were susceptible to Cephalos-porovl, Amikacin, Enrofloxacin and 87.5% of E.coli tested were susceptible to Gentamicin, Kanamycin, Polymyxin, Tetracycline. Immunogenicity and related antigenicity of isolated strains from 8 farms were detected by serological method. The results shown that 3 strains had good immunogenicity and the antibody titer reached 1:5120. 89.29% test E.coli were reacted with the three antisera diluted to 80 times in agglutination test, sharing high antigenicity. Plasmids from isolated E.coli were analized by molecular biological method. Isolation rate of plasmid was 95.83%(23/24) and 6 plasmid patterns with molecular weight of 1.3×103~1.9×104 bp were seen. Bacterial protein structure analysis by sodium doedecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) shown that there were 18~23 protein bands with different size and the molecular weight(5~100 kDa). In western blotting, the antisera could combinate with 70kD or 32kDa proteins of E.coli. It will provide some reference for the therapy of bovine subclinical mastitis and halp to select candidate subunit vaccines against bovine subclinical mastitis.