Staphylococcus aureus isolates from Irish domestic refrigerators possess novel enterotoxin and enterotoxin-like genes and are clonal in nature.
A previous study carried out by the National Food Centre in Dublin on bacterial contamination of Irish domestic refrigeration systems revealed that 41% were contaminated with Staphylococcus aureus. One hundred fifty-seven S. aureus isolates were screened by multiplex PCR analysis for the presence of 15 staphylococcal enterotoxin and enterotoxin-like genes (sea-see, seg-sei, selj-selo, and selq) and the toxic shock toxin superantigen tst gene. Of the refrigerator isolates, 64.3% possessed more than one staphylococcal enterotoxin or staphylococcal enterotoxin-like gene. All bar one of the 101 staphylococcal enterotoxin or staphylococcal enterotoxin-like gene-positive strains possessed the egc locus bearing the seg, sei, selm, seln, and selo genes. Twelve random amplified polymorphic DNA (RAPD) types accounted for 119 (75.8%) of the strains, two of these types accounting for 25 (RAPD type 1, 15.9%) and 52 (RAPD type 5, 33.1%), respectively. All of the RAPD type 5 isolates possessed the egc gene cluster only. The RAPD type 5 amplicon profile was identical to that of S. aureus isolates associated with osteomyelitis in broiler chickens in Northern Ireland that also possessed the egc locus only. However, the RAPD type 5 domestic refrigerator and chicken isolates differed in penicillin G sensitivity, production of Protein A and staphylokinase, and crystal violet agar growth type. These findings highlight that the average Irish household refrigerator harbors potential enterotoxin-producing S. aureus that may or may not be of animal origin and, accordingly, is a potential reservoir for staphylococcal food poisoning.
Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, University of Dublin, Dublin 2, Ireland.
Davida S
DS
Smyth
Jean
J
Kennedy
Jane
J
Twohig
Helen
H
Miajlović
Declan
D
Bolton
Cyril J
CJ
Smyth
D000818:Animals; D003257:Consumer Product Safety; D004269:DNA, Bacterial / Q000032:analysis*; D004768:Enterotoxins / Q000235:genetics*; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D007494:Ireland; D019105:Random Amplified Polymorphic DNA Technique; D012034:Refrigeration; D013202:Staphylococcal Food Poisoning / Q000453:epidemiology / Q000517:prevention & control; D013211:Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification*
D004269:DNA, Bacterial; D004768:Enterotoxins