Analysis Of Virulence Characteristics And Antibiotic Resistance Of Staphylococci In Mastitis Milk Isolated From Guangdong,China

Mastitis is one of the most common diseases and hard to cure in dairy farms with huge economic losses to dairy industry, bacterial infection is always the main pathogens of bovine mastitis. To find more effectively measures, we evaluated the major pathogens and coagulase negative staphylococci(CNS) macrophage cytotoxicity, virulence distribution and antibiotic resistance.We collected 110 mastitis milk samples from 6 farms in Guangdong province. The results showed that 28 kinds of pathogenic bacteria were isolated, bacterial mixed infection was highest prevalence accounting for 67.3%,environmental pathogenic bacteria accounted for 97.4%, infectious pathogenic bacteria 2.6%. The most important pathogen was staphylococci(13.7%), in addition, 40 CNS and 8 staphylococcus aureus were isolated, and CNS isolation rate was as high as 83.3%. Staphylococcus haemolyticus was the mainly CNS, accounting for 45%.Cytotoxicity detection showed that CNS cytotoxicity on macrophage was moderate and above, accounting for 87.5%. Virulence gene detection showed that most prevalent gene fnbp, the rate was 17.5%, followed by tsst and seb, and the rate both were 15%. There were 15 kinds of virulence genes combination, the most prevalence gene combination was tsst, followed by fnbp and seb+sec.CNS drug sensitivity test showed that CNS were sensitive to oxacillin, cefotaxime and ceftriaxone, but to streptomycin, erythromycin and penicillin G the drug resistance rate was 50%, 47.5% and 42.5% respectively. There were 15 kinds CNS resistance phenotyp, and muti drug resistance rate were 35%. Drug resistance gene detection showed that 20% CNS had detected the quinolone resistance gene qnr A, qnr B, qnr C and qnr D, 10% CNS had detected the aminoglycoside resistance gene aac6-aph2 and beta lactam resistance gene blaz respectively. A total of 8 kinds of resistant genotype were detected and highest prevalent genotype was qnr D. 22.5% CNS had one resistance gene and 2.5% CNS had 2, 3 and 4 resistance genes. Disinfectant resistant gene detection showed that 32.5% CNS had disinfectant resistant genes, and the highest prevalent gene was qac G, accounting for 25%. A total of 4 disinfectant resistant genotypes were detected, and the highest prevalent genotype was qac G, accounting for 10%. 27.5% CNS had one disinfectant resistant gene and 2.5% CNS had 2 kinds of disinfectant resistant genes.In summary, mastitis was caused by mixed infection with CNS, cytotoxicity of CNS was high, and there were different degrees of resistance to commonly used antibiotic drugs and disinfectants, and multiplex drug resistance. It needs to study more about environment pathogen such as CNS isolated from mastitis in Guangdong province.