MLST Typing And Identification,Antimicrobial Resistance Of Streptococcus Uberis From Bovine Mastitis

Streptococcus uberis is an environmental pathogen that causes recurrent mastitis in dairy cows.It is a gram-positive cocci and can cause a decrease in milk production and quality.However,there are relatively few studies on the antimicrobial resistance phenotypic and genotypic of Streptococcus uberis in dairy cows.Antibiotics are the main method to treat S.uberis dairy cow mastitis.However,with the extensive use of antibiotics in the clinic,The continued production of antimicrobial-resistant strains poses great difficulties in the prevention and treatment of bovine mastitis in dairy cow mastitis.Thus,the aims of this study were to isolate and identify the Streptococcus uberis,and evaluate the antimicrobial drug resistance of Streptococcus uberis,to assess their antimicrobial resistance profiles,and to analyze the phenotypic and genotypic profiling of resistant isolates,so as to provide guidance for veterinary clinical medication of dairy cow mastitis caused by Streptococcus uberis.First,430 clinical mastitis milk samples were collected from 17 large-scale dairy herds in 8 provinces(municipalities,autonomous regions)of China,and 53 Streptococcus uberis isolate strains were recovered(12.3%)from the clinic mastitis milk samples.Secondly,we applied Multi-locus sequence typing(MLST)method to differentiate Streptococcus uberis isolates and facilitate an understanding of the population biology of this pathogen.The results show that there are 23 ST types of Streptococcus uberis in dairy cows in my country;ST type of isolates of Streptococcus uberis in dairy cows is mainly ST1294,which accounts for 15.1%of the total number of isolates.Therefore,it can be inferred that the ST1294 Streptococcus uberis,which is the leading cause of dairy cow mastitis caused by Streptococcus uberis,is a potential public health risk in my country.Finally,according to the Clinical and Laboratory Standards Institute(CLSI)M24-A2 and M7-A9 documents,To determine the minimum inhibitory concentration of different drugs against different strains by the micro broth dilution method(Minimum inhibition conccntrations,MIC),select seven maj or categories of tetracyclines,macrolides,β-lactams,cephalosporins,lincomycins,penicillins and aminoglycosides,a total of 7 animal clinical antibiotics(tetracycline,erythroderma Ceftriaxone,penicillin,ceftriaxone,cefotaxime,clindamycin,kanamycin,etc.,and a drug commonly used in clinical treatment of streptococcus(meropenem)for Streptococcus uberis isolates drug sensitivity Sexual analysis in order to achieve the detection of drug-resistant phenotypes of each strain of Streptococcus breast.The results of the MIC test indicate that Streptococcus uberis showed different degrees of resistance to selected antibiotics,The resistance rates from high to low were penicillin(47.2%),erythromycin(41.5%),tetracycline(39.6%),meropenem(33.9%),clindamycin(32.2%),and cefotaxime(28.3%).%)and ceftriaxone(26.4%).The main drug resistance genes of each isolate were tested,and the results showed that blaTEM-89 gene and Aph-3’ gene were detected in all strains,and tetS gene was detected in 20 strains of Streptococcus uberis,followed by ermB,ermA,tetO,TetL,tetM,and tetT were 9 strains,8 strains,4 strains,3 strains,3 strains and 2 strains respectively,and only 1 strain had the tetW gene detected.