The Study On PCR-Based Genotyping Of Bovine Source Staphylococcus Aureus

Staphylococcus aureus is the major pathogenic bacteria cause the bovine mastitis, which spread widely and easy to generate the drug resistance. Due to the advantages of high typing rate and discrimination, well reproducibility, easy to interpret, the genotyping based on the PCR technique has been widely used on the Homo sapien and bovine source typing research. It is very important for understanding the genotype of the different districts of our country and definite the connection between the typing and the pathogenicity of S. aureus, which may provide the significance on prevention and cure bovine mastitis.Firstly, the suspected strains of S. aureus isolated from the bovine mastitis milk which spread forty dairy herds of five different provinces undertake fractional cultivation, biochemical text and PCR identity. Then three PCR-based methods such as Protein A gene polymorphism typing (spa typing), MLVA (multiple-locus variable-number tandem repeats analysis) typing and coagulase gene polymorphism typing (coa typing) been used for genotyping of the identified S. aureus respectively. To assessment the discrimination power of each typing method, Formula index of discrimination has been used to compare the results of the typing. Finally, to detect the methicillin-resistance of bovine source S. aureus and analysis the distribution of different genotyping and methicillin-resistance strains, the mecA gene of S. aureus have been identify through PCR amplification.Through identification, fifty-four isolated strains have the typical biology characteristics and definite as S. aureus. These isolated strains and standard strain Wood46 undertake the spa typing, MLVA typing and coa typing, the typing result respectively is fourteen, eighteen and seven types; the index of discrimination is 0.870,0.888,0.847 respectively; The rate of typablity is 98.18%, 100%, 100% respectively. We found three new types t2756,t2759 and t2788 in the spa typing method, which comfirmed by the database of spa typing (http://www.ridom.de/spaserver/). Though the detection and sequencing the methicillin-resistance gene of the isolated strains, one strain is identify as methicillin-resistance Staphylococcus aureus (MRSA), the positive rate is 1.85%, the spa typing of positive strain is t899.From the results above, three PCR-based typing methods all have the higher rate of reproducibility and typablity, spa typing and MLVA typing suit to clinical analysis; though the cost of spa typing is relative higher than the MLVA typing, but reproducibility is fairly well, which easy to comparison among the different laboratories. The coagulase polymorphism typing could be as a useful assist method. The research confirms the methicillin-resistance Staphylococcus aureus (MRSA) have been infection among the bovine herds.