Abstract:

Objective: To investigate the drug resistance of Staphylococcus aureus in animal food in Sichuan, and analyze the Staphylococcus aureus contamination situation. Methods: 2560 samples of animal food (from pig, cattle and chicken ) were collected from December 2006 to September 2007 in Sichuan, then the isolation and identification of Staphylococcus aureus were conducted using selective medium and biochemical test. Results: 118 doubtful strains were isolated according to the growth characteristics on Baird-Parker plate. Among them, 108 strains were regarded as Staphylococcus aureus based on the results of Gram staining, hemolytic crisis and coagulase experiments stipulated in the GB (Chinese national standard), but 113 strains were regarded as Staphylococcus aureus by CHROMagar chromogenic medium and fork index identification stipulated in the TH-16S, whereas only 76 strains, 64% of 118 doubtful strains were further identified as Staphylococcus aureus by 16 biochemical experiments stipulated in the TH-16S. According to GB, the positive rate of SA in 2560 samples was 4.21%, in which, the positive rate of Staphylococcus aureus in raw milk was the highest (10.54%), followed by the pork (7.11%), and that in fresh eggs was zero. Conclusion: The biochemical phenotype of Staphylococcus aureus in Sichuan animal food is complicated, which indicates defects of the conventional phenotypic analysis. The contamination of Staphylococcus aureus in various places shows certain differences. Compared to other reports, the positive rates of Staphylococcus aureus in Sichuan animal foods is relatively low.

Key words: Staphylococcus aureus, animal food, isolation, identification