FOOD SCIENCE ›› 2020, Vol. 41 ›› Issue (20): 285-291.doi: 10.7506/spkx1002-6630-20190714-184

• Safety Detection • Previous Articles     Next Articles

Molecular Characteristics and Antimicrobial Susceptibility of Foodborne Methicillin-Resistant Staphylococcus aureus in Shanghai, China

ZHANG Pengfei, ZHANG Jie, LIU Xinyu, FU Xueting, ZHANG Meng, XU Xuebin, WU Congming, JI Hua, WANG Xin   

  1. (1. College of Food Science and Engineering, Northwest A&F University, Yangling 712100, China;2. Laboratories of Microbiology, Shanghai Municipal Center for Disease Control & Prevention, Shanghai 200336, China; 3. College of Veterinary Medicine, China Agricultural University, Beijing 100193, China;4. College of Food Science, Shihezi University, Shihezi 832000, China)
  • Online:2020-10-25 Published:2020-10-23

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Abstract: Objective: To evaluate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains from different types of food in Shanghai, and investigate the molecular characteristics and antibiotic resistance of these strains. Methods: A total of 184 foodborne S. aureus strains were collected in Shanghai during 2011–2016 for this study. MRSA positive strains were identified by detection of the mecA gene using polymerase chain reaction (PCR) and were further characterized by staphylococcus protein A (spa) typing, multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec (SCCmec) typing, and their antimicrobial susceptibility and virulence genes were also evaluated. Results: Nine (4.9%, 9/184) positive MRSA isolates were identified from the 184 strains, among them one strain was isolated from eggs, one strain from ready-to-eat salads, three strains from raw meat products and the remaining four strains from cooked meat products. All MRSA strains were multidrug-resistant (MDR), being most frequently resistant to ampicillin and penicillin (100%, 9/9), followed by cefoxitin and trimethoprim/sulfamethoxazole (88.9%, 8/9), erythromycin (55.6%, 5/9), amoxicillin/clavulanic acid (33.3%, 3/9), tetracyclines and oxacillin (22.2%, 2/9) and ciprofloxacin (11.1%, 1/9). The carrying rates of the hemolysin genes (hla, hlb and hld) and the panton-valentine leukocidin gene (pvl) were high, while the carrying rates of all enterotoxin genes were low. ST59-IVa-t437 (33.3%, 3/9) and ST88-III-t14340 (22.2%, 2/9) were the most predominant clones, followed by ST398-IVa-t034, ST630-III-t4549, ST5-II-t002 and ST4495-t10738 (11.1%, 1/9 each). Conclusion: Our findings indicated that the foodborne MRSA strains mainly contaminated animal products and artisanal foods at a low level in Shanghai. These foodborne MRSA strains shared the same molecular profiles as LA-MRSA, CA-MRSA and HA-MRSA. Despite the low contamination rate of the MRSA in food, there could be a potential risk of transmission through the food chain.

Key words: methicillin-resistant Staphylococcus aureus; virulence genes; antimicrobial susceptibility; molecular typing

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