Temporal Expression of Staphylococcal Enterotoxin K (sek) Gene in Three Isolates from Food Samples

doi:10.7506/spkx1002-6630-201613025

Abstract

Abstract:

Objective: The newly identified staphylococcal enterotoxin sek gene is found to be very popular in clinical
methicillin-resistant S. aureus isolates. The study of sek gene temporal expression would provide some valuable information
and new data for food poisoning prevention and disease control linked to this bacterium. Methods: Three strains (SA005,
SA008 and SAB0) with sek gene from foodborne isolates in our lab were selected by PCR detection of 21 different SEs
genes. The growth curves of three strains were monitored during the growth phase in TSB. Total RNAs from three strains
were extracted at different growth periods, and a quantitative real time-PCR was developed to monitor the relative expression
of sek gene. Results: The results of virulence gene detection showed that SA005 harbored 16S, nuc, mecA, seb, sec, sek and
sex genes, SA008 harbored 16S, nuc, mecA, sea, sek and sex genes, and SAB0 harbored 16S, nuc, sek and sex genes. The
characteristics of growth curves for three strains had similarity, which exhibited a turning point around 18 h, and then entered
the stationary growth phase. mRNA expression levels were shown during all the growth phases (12–120 h); however, there
were very obvious differences among three strains and among different sampling points. The relative expression of sek gene
was very high at 48 h and very low at 84 h for SA005. For SA008, it was very high at 24 h, very low at 48 h, and was stable
between 60–120 h. The relative expression of sek gene in SAB0 presented a parabolic trend, with a high level at 60 h and
72 h (P > 0.05). Conclusion: The relative expression of sek gene among three strains had a significant difference. Even in the
same strain, the relative expression of sek gene was different at different time points. Strain-to-strain variations with different
background genes may be the key points for different expression patterns of sek gene.

Key words: Staphylococcus aureus, newly identified enterotoxins, sek gene, real time-polymerase chain reaction (real time- PCR), temporal expression

CLC Number:

TS207.4

WANG Qiong, TANG Junni, TANG Cheng, CHEN Juan, LIU Ji, CAI Zijian. Temporal Expression of Staphylococcal Enterotoxin K (sek) Gene in Three Isolates from Food Samples[J]. FOOD SCIENCE, doi: 10.7506/spkx1002-6630-201613025.

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