Multilocus Sequence Typing and Virulence-Associated Gene Profile Analysis of Staphylococcus aureus Isolates From Retail Ready-to-Eat Food in China.

Xiaojuan Yang,Shubo Yu,Shi Wu,Dongli Rong,Jumei Zhang,Qingping Wu

doi:10.3389/fmicb.2018.00197

Abstract

The aim of this study was to characterize the subtypes and virulence profiles of 69 Staphylococcus aureus isolates obtained from retail ready-to-eat food in China. The isolates were analyzed using multilocus sequence typing (MLST) and polymerase chain reaction (PCR) analysis of important virulence factor genes, including the staphylococcal enterotoxin (SE) genes (sea, seb, sec, sed, see, seg, seh, sei, sej), the exfoliative toxin genes (eta and etb), the toxic shock syndrome toxin-1 gene (tst), and the Panton-Valentine leucocidin-encoding gene (pvl). The isolates encompassed 26 different sequence types (STs), including four new STs (ST3482, ST3484, ST3485, ST3504), clustered in three clonal complexes and 17 singletons. The most prevalent STs were ST1, ST6, and ST15, constituting 34.8% of all isolates. Most STs (15/26, 57.7%) detected have previously been associated with human infections. All 13 toxin genes examined were detected in the S. aureus isolates, with 84.1% of isolates containing toxin genes. The three most prevalent toxin genes were seb (36.2%), sea (33.3%), and seg (33.3%). The classical SE genes (sea–see), which contribute significantly to staphylococcal food poisoning (SFP), were detected in 72.5% of the S. aureus isolates. In addition, pvl, eta, etb, and tst were found in 11.6, 10.1, 10.1, and 7.2% of the S. aureus isolates, respectively. Strains ST6 carrying sea and ST1 harboring sec-seh enterotoxin profile, which are the two most common clones associated with SFP, were also frequently detected in the food samples in this study. This study indicates that these S. aureus isolates present in Chinese ready-to-eat food represents a potential public health risk. These data are valuable for epidemiological studies, risk management, and public health strategies.

Highlights

The facultative anaerobe Staphylococcus aureus is the leading cause of both nosocomial infections and community-acquired infections worldwide, causing many serious illnesses (Rodríguez-Lázaro et al, 2015; Yang et al, 2016)
To assess the potential virulence and risk posed by these 69 S. aureus isolates from RTE food, we provide a phylogenetic framework for these isolates in the current study, based on multilocus sequence typing (MLST) analysis and screened for the presence of virulence-associated genes
All 13 toxin genes examined were detected in the 69 S. aureus isolates

Summary

Introduction

The facultative anaerobe Staphylococcus aureus is the leading cause of both nosocomial infections and community-acquired infections worldwide, causing many serious illnesses (Rodríguez-Lázaro et al, 2015; Yang et al, 2016). MRSA (HA-MRSA), community-acquired MRSA (CA-MRSA), and livestock-associated MRSA (LA-MRSA) strains, exhibit resistance to all β-lactam antibiotics through acquisition of the mobile staphylococcal cassette chromosome mec (SCCmec) and constitute a major health concern. Staphylococcus aureus possesses various virulence factors that are implicated in pathogenesis, such as the staphylococcal enterotoxins (SEs), toxic shock syndrome toxin-1 (TSST-1), the exfoliative toxins A and B (ETA and ETB), and PantonValentine leukocidin (PVL) (Wang et al, 2012, 2014; Song et al., 2015). PVL causes necrotizing pneumonia, sepsis, and severe tissue damage (Lina et al, 1999; Yamamoto et al, 2013) The presence of these virulence factors in S. aureus isolates from food may pose a threat to public health

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