Plasmid profiles and pulsed-field gel electrophoresis for type a enterotoxigenic staphylococcus aureus isolated from foods

Abstract

Reports regarding the use of plasmid profile and pulsed-field gel electrophoresis (PFGE) in subtyping of specific enterotoxigenic Staphylococcus aureus isolated from food samples are limited. We isolated 176 strains of S. aureus from food samples and showed that 64 of these strains are enterotoxigenic as determined by staphylococcal enterotoxin A, B, C, D detection kit by reversed passive latex agglutination (SET-RPLA) method. Of these 64 enterotoxigenic strains, 45 by SET-RPLA or 44 by polymerase chain reaction (PCR) were identified to be staphylococcal enterotoxin A (SEA) producing strains. All these 64 enterotoxigenic strains could be grouped into three patterns of antibiogram when their antibiotic susceptibilities to penicillin G, oxacillin, vancomycin and methicillin were investigated. Strains resistant to penicillin G, but susceptible to the other three antibiotics were of the major pattern since 50 of the 64 enterotoxigenic strains tested showed such pattern of antibiotic susceptibility. Plasmid deoxyribonucleic acid (DNA) analysis for the 45 SEA strains showed that four types of plasmid profiles could be obtained. When chromosomal DNA of these SEA strains were digested with Smal and subjected to the PFGE analysis, a total of eight genome types were observed. In addition, 28 of these 45 SEA strains tested could be grouped into one specific type of these eight genome types. Results shown in this report may be useful for the epidemiological study and for the tracing of contamination source when a food poisoning outbreak occurs. Copyright © International Association of Milk, Food and Environmental Sanitarians.