Molecular analysis and antibiotic resistance investigation of Staphylococcus aureus isolates associated with staphylococcal food poisoning and nosocomial infections

Abstract

Enterotoxins (SEs) generated by Staphylococcus aureus were considered to be the main reason for staphylococcal food-poisoning (SFP). The aim of this research is to investigate the distribution difference of enterotoxin genes in strains isolated from food, food poisoning, inpatients, respectively. Multiplex polymerase chain reaction (PCR) was employed to detect SEs and relationship between anti-biotic resistance and living conditions of S. aureus has also been analyzed. Pulsed-Field Gel Electrophoresis (PFGE) was further applied for the determination of the genetic relationships between S. aureus isolates. It was striking to found that positive detection ratio of multi-enterotoxin genes and newly found enterotoxin genes in inpatients’ isolates were higher than the other two (P<0.01). SEG, SEI, SEK, SEQ genes were mainly presented in isolates from inpatients while, SEA, SEE, SHE, SEQ genes mainly presented in isolates from food samples and SEA, SEP, SEC genes mainly found in strains from food poisoning. The most important fact was that percentages of isolates from inpatient resistant to oxacillin were 71.43%, which was significantly higher than the percentages (2.33% and 2.38%) of the other two original isolates. The similarity among these isolates was above 70% and PFGE was agreed to be a useful discriminating typing method for S. aureus isolates.

Key words: Staphylococcus aureus, enterotoxin genes, antibiotic resistance.