| Slaphylococcus aureus is a common zoonoses and important for Clinical Medicine and Veterinary to research its resistance. The overuse and misuse of antimicrobial agents in farms leaded to the resistance of Staphylococcus aureus in animals increasingly serious. Susceptibility testing, detection of the major resistance genes and Molecular epidemiology may help us to find the trend of its production and dissemination of resistance, and provide theoretical basis for standardized use of drug.In this study,236 strains of Staphylococcus aureus were isolated from animals from 2007 to 2013. A standard broth microdilution method, as described by the Clinical and Laboratory Standards Institute (CLS1,2011), was carried out to determine the minimum inhibitory concentration (MIC) of 11 antimicrobial agents. The results showed that, the strains showed high level susceptibility to oxacillin (more than 80%). the rate of resistance to other 10 antimicrobial agents were more than 20%, followed by penicillin 92.8%, ampicillin 90.25%, gentamicin 47.88%, kanamycin 36.87%, amikacin 39.83%, erythromycin 77.12%, azithromycin 58.47%, tetracycline 40.68%. ciprofloxacin 26.28%. sulfonamides isoxazole 87.71%. Multi-resistance was sebere among the Staphylococcus aureus isolates, most of it exhibited multidrug-resistance to 6 and 9 antimicrobial agents.The strains showed an upward trend rate of resistance to different antimicrobial agents for overtime. The strains isolated form pig showed significantly higher rate of resistance to erythromycin and azithromycin than isolated from chicken (P<0.05). Staphylococcus aureus isolated from different animal had not been showed significant difference on the remaining 9 antimicrobial agents resistance rate (P>0.05). The phenomenon of multi-drug resistance of 236 Staphylococcus aureus isolates was severe.159 (67.37%.159/236) of Staphylococcus aureus isolates were plasma coagulase positive strains by using the tube method in the study, We found that the resistance rate of plasma coagulase positive strains to penicillin, oxacillin, gentamicin, kanamycin, amikacin. ciprofloxacin were significantly higher than that of coagulase negative strains (P< 0.05). Furthermore, plasma coagulase positive strains exhibited more widely Multi-drug resistant spectrum than plasma coagulase negative strains. No strain was detected to be the positive strain of virulence genes:pvl and tst.In this study, the blaZ-mecA dual PCR system and the aacA-aphD-ermA-mecA triple PCR system were designed, and the normal PCR systems which to amplify the six genes:blaZ, mecA, aacA-aphD, ermA, ermB, ermC were also designed. The PCR amplifications of different genes showed that, the rate of β-lactam resistance genes of 236 strains was:blaZ 63.98% and mecA 10.59%, macrolides, lincosamide, streptogramin B resistance genes:ermA 11.44%, ermB 83.05% and ermC 87.29%. Aminoglycosides resistant gene:aacA-aphD 43.64%, respectively. The mainly resistance gene combinations were blaZ+ermB+ermC and blaZ+ermB+ermC+aacA-aphD. As time goes by. the strains carried more resistance genes.SCCmec typing of 24 MRSA isolates was performed. The result showed that all the strains isolated in 2008 and 2009 were HA-MRSA (70.83%). and others was CA-MRSA (20.83%) isolated in 2013. SCCmec type Ⅲ is the most common SCCmec type, which was present in 12 isolates(50%). The 24 MRSA is divided into 14 cluster groups by PFGE, named A-N. The major type was J which accounted for 25%(6/24).These results suggest that Staphylococcus aureus isolated from different animals in Sichuan showed different levels to to different antimicrobial agents and the rate of resistance was growth over time, the clinic veterinary should be strengthened resistance monitoring of Staphylococcus aureus:Staphylococcus aureus isolated from different animals were detected to be a high rate of plasma coagulase-positive (67.37%), and plasma coagulase-positive bacteria exhibted a more serious multi-drug resistant strains than negative, it indicated that pathogenic strains existed long-term and widespread in Staphylococcus aureus. and we should strengthen the detection of coagulase strains and resistance. The detection of MRSA SCCmec types were complex, which mainly was SCCmecⅢ type, and SCCmec type Ⅲ strains carried more resistant genes than other SCCmec types. With the passage of time separated, Strain gradually changed from HA-MRSA to CA-MRSA and carried more resistance genes. MRSA strains were polyclonal popular, so the clinic veterinary should continue to strengthen monitoring of MRSA epidemic for long-term. |
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