Isolation,Identification And Drug Resistance Analysis Of Bovine Mammary Pathogenic Streptococcus In Jilin Province

As a disease that plagues the livestock industry all over the world,Bovine mastitis has brought incalculable economic losses to the livestock industry around the world every year.Streptococcus agalactiae,Streptococcus dysgalactiae,and Streptococcus uberis are all of the genus Streptococcus,and their morphological and biological characteristics are similar,and their genetic composition is similar.They are all pathogenic microorganisms that can cause milk cow mammary gland infections.Epidemiological surveys in recent years have shown that the incidence of mastitis in dairy cows in Jilin Province is high and drug resistance is serious,and there is a lack of comprehensive and systematic scientific investigations.Conventional bacterial isolation and identification methods are time-consuming and labor-intensive,and the cycle is long,which is not conducive to the rapid diagnosis of the disease.In addition,the widespread use of veterinary antibiotics in my country,and the unreasonable and unstandardized clinical use of antibiotics has led to a serious problem of bacterial resistance.Therefore,it is of great significance to establish an efficient and rapid detection method to carry out the differential diagnosis of dairy cow mastitis cases in the whole province,and to carry out systematic and scientific drug resistance analysis for the prevention and treatment of dairy cow mastitis in Jilin Province.In this study,a bovine mammary gland pathogenic Streptococcus was used as the research object,and a triple real-time quantitative PCR method was established for the simultaneous rapid detection of Streptococcus agalactiae,Streptococcus uberis and Streptococcus dysgalactiae.Methods and 16 S r RNA PCR methods were used to isolate and identify Streptococcus in 720 milk samples of dairy cow mastitis cases from 18 farms in 9 regions of Jilin Province;The three isolated and identified streptococcus strains were subjected to multi-locus sequence(MLST)typing,and the pathological models of murine mastitis with different ST types were established.Finally,the screening of drug resistance genes and drug susceptibility tests were carried out to conduct a systematic and comprehensive investigation and research on mammary pathogenic Streptococcus in Jilin Province.The results show that the triple real-time PCR method established in this study has good sensitivity,specificity,and strong stability,and can be applied to rapid laboratory diagnosis.A total of 59 milk samples with mastitis were detected in Jilin area,and 49 strains of Streptococcus were successfully isolated from them,including25 strains of Streptococcus agalactiae,7 strains of Streptococcus uberis,and 17 strains of Streptococcus dysgalactiae.MLST typing results showed that 49 strains produced a total of 10 ST types.The phylogenetic tree was constructed to show that the mammary gland pathogenic Streptococcus in Jilin region is far from the other regions of the world.The histopathological results of mouse mastitis with 10 ST-type strains showed that different ST-type strains all caused infection to mouse mammary tissue,with obvious clinical symptoms.Histopathological observation showed that mammary alveolar epithelial cells were lysed,exfoliated and necrotic.Bacterial virulence varies greatly among different Streptococcus strains.The results of bacterial resistance study showed that among the 49 strains,12 resistance genotypes of 5 antibiotics under the mechanism of antibiotic target protection,antibiotic target change,antibiotic inactivation,and antibiotic efflux were detected.The results of PCR amplification test and MIC test showed that most of the Streptococcus in Jilin area were multi-drug resistant bacteria,and the bacterial resistance was serious.Penicillin was still the first choice for treatment.To sum up: In this study,continuous innovation was made in the molecular biology diagnosis technology of pathogenic microorganisms,and the multiplex fluorescence quantitative PCR detection method of Streptococcus agalactiae,Streptococcus dysgalactiae,and Streptococcus uberis was successfully established,and the pathogenicity of mammary glands in Jilin area was established.A comprehensive screening of Streptococcus was carried out,through MLST typing,pathological model construction and drug resistance analysis,for the diagnosis and traceability of mammary pathogenic Streptococcus in Jilin area,research on the distribution characteristics of drug resistance genes and dairy cattle breeding.Provide scientific guidance and technical support for drug use.