Molecular characteristics of Staphylococcus aureus isolates from food surveillance in southwest China

Feng Liao,Wenpeng Gu,Jiejie Dai,Lu Fan,Wen Xu,Yidan Guo,Zushun Yang,Zhishuo Mo,Xiaoqing Fu,Chaoqun Li

doi:10.1186/s12866-018-1239-z

Abstract

BackgroundStaphylococcal food poisoning (SFP) is one of the most common food-borne diseases in the world. Pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and spa typing methods were used to characterize Staphylococcus aureus isolates from food surveillance during 2013–2015 in southwest China, and Staphylococcal cassette chromosome mec (SCCmec) typing was used for methicillin-resistant S. aureus (MRSA). Isolates were also examined for their antibiotic resistance and carriage of virulence genes.ResultsIsolation rate of S. aureus was 2.60% during the three years’ surveillance and 29.50% of them were MRSA. All the S. aureus had hla genes (100%), 14.34% of the strains had tst, and 16.73% had PVL. 163 PFGE-SmaI patterns, 41 ST types and 36 spa types were obtained for all the S. aureus. Among them, ST6-t701 (13.15%), ST7-t091 (12.75%), ST59-t437 (9.96%) and ST5-t002 (7.57%) were the prevalent genotypes. Most of MRSA in this study belonged to SCCmec IV and V, accounted for 74.32% and 20.27% respectively. ST6-SCCmec IV-t701 (36.50%) was the most prevalent clone among isolates from food, followed by ST59-SCCmec V-t437 (20.30%), ST5-SCCmec IV-t002 (12.20%) and ST59-SCCmec IV-t437 (12.20%). Some strains had the identical PFGE patterns, ST and spa types with isolates from patients.ConclusionsS. aureus isolated from food in southwest China displayed heterogeneity. Isolates had the same genotype profiles with isolates from patients, indicating high homology.

Highlights

Staphylococcal food poisoning (SFP) is one of the most common food-borne diseases in the world
A total of 251 S. aureus strains were isolated from food, 56% (139/251) from grain products, 31% (78/ 251) from meat products and 6% (16/251) from dairy products, these strains accounted for 93% of all the isolates (Fig. 1b)
The comparison of S. aureus isolates from patients and food was performed; the results showed that some strains from patients had identical Pulsed-field gel electrophoresis (PFGE) patterns, ST and spa types with food isolates, indicated high homology relationship

Summary

Introduction

Staphylococcal food poisoning (SFP) is one of the most common food-borne diseases in the world. Pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and spa typing methods were used to characterize Staphylococcus aureus isolates from food surveillance during 2013–2015 in southwest China, and Staphylococcal cassette chromosome mec (SCCmec) typing was used for methicillin-resistant S. aureus (MRSA). The toxigenic S. aureus strains associated with SFP can express one or more of a family of genes coded for heat-stable enterotoxins. These genes showed high sequence homology in their structure and functions [1]. The major molecular typing methods for S. aureus were pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), spa typing and Staphylococcal cassette chromosome mec (SCCmec) typing [10,11,12,13]. SCCmec developed by International Working Group on the Classification of Staphylococcal Cassette Chromosome Elements, (IWG-SCC: www.sccmec.org) was mainly used for genotyping of MRSA [14]

Methods

Results

Discussion

Conclusion