Abstract: In order to monitor and assess the contamination level of Staphylococcus aureus in cold noodles, a total of 432 cold noodles samples were collected from supermarkets, street vendor stalls, restanuants and campus canteens in Yangling, Shaanxi Province and screened for S. aureus over one year. Of these, 105 samples (24.3%) were positive for S. aureus, and the S. aureus isolates were characterized by anti-microbial susceptibility testing and PCR for detecting nine enterotoxin genes (sea to sej). All the isolates were found positive for at lest one enterotoxin gene. The genes sea (96.2%) was detected in almost all the isolates, followed by see (64.8%), and seb and sec were also found in 57 (54.3%) and 52 (49.5%) and she in only one (1.0%) of these 105 isolates. On the other hand, sed, seg, seh, sei, and sej were not found. In addition, all the S. aureus isolates were resistant to at least one of 14 common antimicrobial agents and 90.5% of them were multiresistant to three or more anti-microbials. Resistance to penicillin and trimethoprim/sulfamethoxazole (each 100.0%) was most frequently detected, and all the isolates were sensitive to ceftriaxone, ciprofloxacin, vancomycin and amikacin. The multi-drug resistance to penicillin ampicillin, trimethoprim/sulfamethoxazole and amoxicillin/clavulanic acid (Pen-Amp-T/S-A/C) was detected in 65 (61.9%) of the 105 isolates and was identied to be the most predominant. Morever, all the isolates were spa typed. A total of 4 different spa types were detected among the 105 S. aureus isolates. The results showed that S. aureus spa-t701 (81.9%) was the most predominant clone, followed by spa-t441 (16.2%),while spa-t127 and spa-t796 were the lowest (each 1.0%). In summary, this study indicates that S. aureus isolated from cold noodles in chain supermarket, street food stalls, and strains have higher drug resistance and probability to carry enterotoxin genes. Morever, the dominant SPA types are t701 and t441. Thus, these findings can provide some theoretical guidance to regulatory authorities concerned.

Key words: Staphylococcus aureus, enterotoxin genes, spa typing, antimicrobial susceptibility