title: Genetic diversity and virulence potential of Staphylococcus aureus isolates from raw and processed food commodities in Shanghai.
abstract: The risk of zoonotic transmission to humans highlights the need to understand the molecular ecology of Staphylococcus aureus in foods. In this study, 142 S. aureus isolates obtained from various raw and processed foods from Shanghai, China were characterized to determine their genetic diversity and virulence gene content. A total of 16 clonal complexes (CCs), 34 staphylococcal protein A (spa) types, and 6 accessory gene regulator (agr) allelic groups were identified and analyzed among the 142 S. aureus isolates. Among these, the genotype CC188-t189-agr Ι was the most prevalent, constituting 28.2% of all isolates. The presence of virulence genes encoding 20 staphylococcal enterotoxins (se), toxic shock syndrome toxin (tsst1), exfoliative toxins (eta, etb, and etd), Panton-Valentine leukocidin (lukS-PV and lukF-PV), as well as methicillin resistance gene (mecA), was determined by PCR. Of these S. aureus isolates, 72.5% harbored toxin genes, in which the most frequent toxin gene was sep (43.7%), followed by sej (26.1%) and pvl (21.1%). In contrast, see, ses, set, tsst1, etb, and etd were not found in any of the isolates tested. Eight S. aureus isolates (5.6%, 8/142), seven from raw milk and one from frozen food, were mecA positive and resistant to oxacillin, thus were MRSA. The 142 S. aureus isolates displayed 52 different toxin gene profiles. Although no direct association was found between toxin gene profile and the S. aureus genotype, the isolates belonging to CC5, CC9, CC20, CC50, and CC72 clonal lineages in general carried more toxin genes (>5) compared with the isolates in other CCs. It was also revealed that raw milk and raw meat were the major sources of isolates containing multiple toxin genes. S. aureus isolates from food that were genetically highly related, displayed diverse toxin gene profiles, implying the significant role of horizontal gene transfer in the emergence of highly toxigenic S. aureus isolates.
authors.affiliation: MOST-USDA Joint Research Center for Food Safety, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
authors.forename: Minghui
authors.initials: M
authors.lastname: Song
authors.affiliation: MOST-USDA Joint Research Center for Food Safety, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
authors.forename: Yalong
authors.initials: Y
authors.lastname: Bai
authors.affiliation: MOST-USDA Joint Research Center for Food Safety, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
authors.affiliation: Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, USDA, Albany, CA 94710, USA.
authors.forename: Michelle Qiu
authors.initials: MQ
authors.lastname: Carter
authors.affiliation: MOST-USDA Joint Research Center for Food Safety, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China. Electronic address: clshi@sjtu.edu.cn.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Shi
authors.affiliation: MOST-USDA Joint Research Center for Food Safety, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China; State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai 200240, PR China. Electronic address: xmshi@sjtu.edu.cn.
authors.forename: Xianming
authors.initials: X
authors.lastname: Shi
mesh_terms: D001427:Bacterial Toxins / Q000235:genetics; D002681:China; D005511:Food Handling; D005516:Food Microbiology; D014644:Genetic Variation; D066256:Raw Foods / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics*; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001427:Bacterial Toxins; D037521:Virulence Factors
keywords: Food commodities; Multi Locus Sequence Typing (MLST); Staphylococcus aureus; Toxin genes; agr typing; mecA