Abstract
A total of 108 S. aureus isolates from 16 major hospitals located in 14 different provinces in China were characterized for the profiles of 18 staphylococcal enterotoxin (SE) genes, 3 exfoliatin genes (eta, etb and etd), and the toxic shock syndrome toxin gene (tsst) by PCR. The genomic diversity of each isolate was also evaluated by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and accessory gene regulator (agr) typing. Of these strains, 90.7% (98/108) harbored toxin genes, in which tsst was the most prevalent toxin gene (48.1%), followed by sea (44.4%), sek (42.6%) and seq (40.7%). The see and etb genes were not found in any of the isolates tested. Because of high-frequency transfer of toxin gene-containing mobile genetic elements between S. aureus strains, a total of 47 different toxin gene combinations were detected, including a complete egc cluster in 19 isolates, co-occurrence of sea, sek and seq in 38 strains, and sec and sel together in 11 strains. Genetic typing by PFGE grouped all the strains into 25 clusters based on 80% similarity. MLST revealed 25 sequence types (ST) which were assigned into 16 clonal complexes (CCs) including 2 new singletons. Among these, 11 new and 6 known STs were first reported in the S. aureus strains from China. Overall, the genotyping results showed high genetic diversity of the strains regardless of their geographical distributions, and no strong correlation between genetic background and toxin genotypes of the strains. For genotyping S. aureus, PFGE appears to be more discriminatory than MLST. However, toxin gene typing combined with PFGE or MLST could increase the discriminatory power of genotyping S. aureus strains.
Highlights
S. aureus is one of the most common clinical and foodborne pathogens
Toxin gene content in S. aureus isolates By PCR amplification of sequence-specific regions in 22 toxin genes, the occurrence of the staphylococcal enterotoxin (SE), exfoliative toxins (ETs) and toxic shock syndrome toxin (TSST) genes in 108 S. aureus isolates was determined
A collection of 108 clinical isolates from China were investigated for the presence of 18 SE and 3 exfoliatin genes, and the toxic shock syndrome toxin gene by PCR and were genotyped by pulsed-field gel electrophoresis (PFGE), Multilocus sequence typing (MLST) and agr typing
Summary
S. aureus is one of the most common clinical and foodborne pathogens. It can cause a wide variety of infections ranging from skin and tissue infections, toxin-mediated diseases, pneumonia, and bacteremia. It has been reported that S. aureus colonizes the skin and mucosal surface of 20 to 40% of humans, implying a high risk of developing the infections of this organism [1]. A recent study found that 47% of meat and poultry in US grocery stores were contaminated with S. aureus, and 52% of those bacteria were resistant to antibiotics [2]. The high prevalence and rapid spread of drug-resistant S. aureus strains in food supplies have increased the risk of S. aureus infections and posed a great threat to food safety and public health
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