Isolation,Identification And Pathogenic Assessment Of Lactococcus Garvieae In Cow Milk

Lactococcus garvieae was initially isolated from mastitis milk,some scholar believes that the bacteria can cause dairy breasts,but there is less research about cows mastitis of Lactococcus garvieae,its infection mechanism was not clear.In order to understand potential pathogenicity of Lactococcus garvieae,one strain of milk borne Lactococcus garvieae was identified by morphological,physiological and biochemical test and molecular biology experiment;3 main Hemolysin genes and 4 main Adhesin genes were detected from isolate strain and Lactococcus garvieae were detected from 109 clinical mastitis milk samples and 95 normal milk samples by PCR method to estimate the potential pathogenicity of milk borne Lactococcus garvieae;The drug resistance test analysis of Lactococcus garvieae on 15 antibiotics was carried out using a drug susceptibility test.The results showed that the isolated bacteria was Gram-stained positive and spherical bacteria;A DNA fragment was amplified by the 16 Sr RNA gene and dna A specific gene primers respectively,the size were 134 bp and 156 bp respectively,its size were consistent with the predicted results;The results of DNA sequence alignment of NCBI gene library showed that the homology of the 16 Sr RNA genes and dna A specific genes of the isolated strain and the same bacteria in Gen Bank have reached 100% and 97.42% respectively,isolated strain was identified as Lactococcus garvieae.7 potential virulence genes were detected in the isolation strain,which were Hemolysin1,Hemolysin2,Hemolysin3,Adhesin Pav,Adhesin Psa A,Adhesin Cluster1,Adhesin Cluster2,? hemolysis occurs on blood agar.The drug sensitivity test results showed that the isolated strain is resistant to Clindamycin,more sensitive to Vancomycin,Tobramycin,Oxacillin,Lincomycin,Norfloxacin and Polymyxin B,most sensitive to Cefazolin,Ciprofloxacin,Gentamicin,Ofloxacin,Kanamycin,Penicillin and Streptomycin.The results of Lactococcus garvieae of cow milk PCR detection test showed 17 positive samples in the clinical mastitis milk sample,positive rate is 16%,6 positive samples in normal milk samples,positive rate is6%,the detection rate of mastitis milk samples is higher than that of normal milk samples.The results of this study provide data support and theoretical basis for the further study of Lactococcus garvieae.