Abstract
Staphylococcal enterotoxins (SEs) are virulence factors of Staphylococcus aureus associated with various toxic diseases due to their emetic and superantigenic activities. Although at least 27 SE(-like) genes have been identified in S. aureus to date, the newly identified SE(-like) genes have not yet been well characterized by their epidemiological features. In this study, the prevalence and genetic diversity of SE gene sey and SE-like genes selw, selx, selz, sel26, and sel27 were investigated for 624 clinical isolates of community-acquired methicillin-resistant S. aureus (CA-MRSA). The most prevalent SE(-like) gene was selw (92.9%), followed by selx (85.6%), sey (35.4%) and selz (5.6%), while sel26 and sel27 were not detected. Phylogenetically, sey, selw, selx, and selz were discriminated into 7, 10, 16, and 9 subtypes (groups), respectively. Among these subtypes, sey was the most conserved and showed the highest sequence identity (>98.8%), followed by selz and selx. The SE-like gene selw was the most divergent, and four out of ten genetic groups contained pseudogenes that may encode truncated product. Individual subtypes of SE(-like) genes were generally found in isolates with specific genotypes/lineages of S. aureus. This study revealed the putative ubiquity of selw and selx and the prevalence of sey and selz in some specific lineages (e.g., ST121) in CA-MRSA, suggesting a potential role of these newly described SEs(-like) in pathogenicity.
Highlights
Staphylococcus aureus is one of the most common pathogens in humans and is responsible for various diseases ranging from skin and soft tissue infections to severe and often deadly infections such as bacteremia [1]
We investigated the prevalence of six staphylococcal enterotoxins (SEs)(-like) genes in community-associated MRSA (CA-MRSA) clinical isolates and revealed a high prevalence of selw and selx, a lower prevalence of sey and selz, and an absence of sel26 and sel27
It was notable that these six genes are distributed to S. argenteus, the prevalence of other SE(-like) genes was very low, except for sec and the enterotoxin gene cluster in some isolates [34]
Summary
Staphylococcus aureus is one of the most common pathogens in humans and is responsible for various diseases ranging from skin and soft tissue infections to severe and often deadly infections such as bacteremia [1]. (TSST-1), is produced by most clinical isolates of S. aureus as etiological factors of toxic diseases including food poisoning and toxic shock syndrome [3]. The prevalence of SE genes including sea-see and seg-selu in S. aureus has been analyzed in many studies of isolates from bacteremia [7,8], diabetic foot ulcers [9], cystic fibrosis [10], and colonization in healthy humans [11,12], as well as those from animals and the environment [13,14,15]. The distribution of SE genes sea-see and seg-seo (or -seu) to clinical isolates of HA- and CA-MRSA was investigated previously [16,17,18], the prevalence of more recently described SE(-like) genes (sey, selw, selx, selz, sel, and sel27) has not yet been well characterized
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