| Bovine mastitis is one of the most common diseases in the dairy farming industry,which can cause the milk production of dairy cows to decrease or even lose.At the same time,with the reduction of milk quality,it causes huge economic losses to the dairy farming industry.The infection of pathogenic bacteria is the main cause of mastitis in dairy cows,and Staphylococcus aureus(SA,S.aureus)is the main pathogenic bacteria causing mastitis in dairy cows.In this study,milk samples from some large-scale dairy farms in southern Xinjiang were collected,and S.aureus was isolated and identified.S.aureus was typed using multilocus sequence typing(MLST)and Staphylococcal protein A(spa)methods.At the same time,the isolates were tested for their antimicrobial sensitivity and biofilm formation ability,and the biofilm formation-related genes and toxin gene carrying rate were evaluated to provide experimental basis for the healthy breeding of dairy cows in southern Xinjiang.MLST analysis results showed that 107 strains of S.aureus belonged to 44 ST types(sequence type),of which 41 ST types were discovered for the first time in this study,accounting for 93.2% of the total ST types determined in this study.Of the 41 new ST types,24 were from the Aksu area and 17 from the Bazhou area.The predominant molecular types in the Bazhou area are ST5406 and ST5405.However,the sequence type of S.aureus in Aksu area is more scattered,and no higher proportion of dominant molecular types have been found.By co-clustering analysis of 44 ST types,it is classified into 5 clonal complexes(CC),of which the two clonal complexes CC81 and CC88 are from Aksu region,and the two clonal complex groups of CC5405 and CC5406 are from Bazhou.Region,CC398 is a clonal complex shared by the two regions.The results of spa typing showed that 107 strains of S.aureus belonged to 9 spa types,of which 4 spa types of t5100,t2970,t2592 and t1764 were from Aksu region,and 4 spa types of t189,t519,t1451 and t571 were from Bazhou.Region,t034 is a spa type common to both regions.The molecular typing results showed the diversity of molecular typing of S.aureus in southern Xinjiang.The sensitivity of 107 strains of S.aureus to 14 kinds of antibacterial drugs was tested by K-B method and micro broth dilution method.The results showed that the isolates showed extremely high resistance to penicillin G,erythromycin and clindamycin,the resistance rates were 72.0%(77/107),64.5%(69/107)and58.9%(63/107).19.6%(21/107)of S.aureus did not show resistance to any of the tested drugs,9.3%(10/107)of the strains showed resistance to 1 antibacterial drug,13.3%(14/107)strains showed sensitivity to 2 antibacterial drugs,57.9%(62/107)strains showed multidrug-resistant(MDR)resistance to 3 or more antibacterial drugs.At the same time,MRSA(Methicillin-resistant S.aureus)test was performed on 107 strains.The results showed that 3 strains were MRSA strains,all isolated from the same area.The microplate semi-quantitative method was used to detect the biofilm formation ability of the 107 isolated strains.The results showed that 12 strains(11.2%,12/107)had strong biofilm formation ability,38strains(35.5%,38/107)showed moderate biofilm formation ability,and 56 strains(52.3%,56 /107)The biofilm formation ability is weak.PCR technology detected genes related to biofilm formation,and found that clfa,clfb,cna,sarA,and sigB were present in all isolates,while bap and agrC were not detected in all strains.The genes with higher detection rate were ccp(94.4%),luxS(87.0%),tcaR(86.0%)and icaA(58.9%).For 15 kinds of virulence genes,including Staphylococcal enterotoxin gene(SE),toxic shock syndrome gene(TSST),hemolysin gene(HL),Pantoxin-Valentine Leukocidin gene(PVL)and Exfoliative toxin(ET)are tested.The detection rate of pvl gene was 54.2%(58/107),and 88.6% of CC5406 strains(31/38)contained pvl gene.The gene detection rate of eta was 26.2%(28/107),and the etb gene was not detected.20.6% of the strains(22/107)contained the tsst gene and only existed in the CC81 and CC5406 clones.The other clones did not detect this gene.The hemolysin gene hlb is present in all strains,and the detection rate of hla gene is 98.1%(105/107).The enterotoxin gene see was not detected in all strains.The detection rates of other enterotoxin genes were sea(12.1%,13/107),seb(4.7%,5/107),sec(24.3%,26/107),sed(41.1%,44/107),seg(1.9%,2/107),seh(25.2%,27/107),sei(57.0%,61/107),sej(5.6%,6/107).Among them,the detection rate of seh gene in S.aureus from Aksu area was 90%(27/30),and the sei gene was present in CC5045(66.7%,22/33)and CC5406(97.4%,37/38)with a high detection rate in two clones.In this study,through molecular analysis and biofilm related detection,toxin gene detection and drug sensitivity integrated analysis,CC5405 and CC5406,as the new cloning complex found in this research,have strong biofilm formation ability and high biofilm gene detection rate.At the same time,these two clonal complexes have a high toxin detection rate.For example,the detection rate of pvl gene and sei gene of CC5406-t519 type is higher than 85%.The CC5405-t189 has high hemolysin gene,sea and seb genes.The resistance rate of CC5406-t519 to erythromycin,penicillin and clindamycin is higher than 80%.Compared with the two clonal complexes,the detection rates of drug resistance and toxin genes of CC81,CC88 and CC398 are relatively low. |
PDF Full Text Request