Staphylococcus aureus Isolates from Irish Domestic Refrigerators Possess Novel Enterotoxin and Enterotoxin-like Genes and Are Clonal in Nature

Abstract

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.

A preventative approach to promote food safety

“…aureus is a common inhabitant of human nose, throat and skin (Arbuthnott et al, 1990, Gundogan et al, 2005, and is more likely to contaminate foods and refrigerators by direct or indirect human contact during domestic food process and storage (Smyth et al, 2006). According to present study visual inspection, 7% of households had weak hygienic condition that can be resulted in contamination by S. aureus.…”

Development and application of loop-mediated isothermal amplification assays on rapid detection of various types of staphylococci strains

“…During 1983–1997, the annual number of staphylococcal food poisoning cases in the USA had been estimated to be 185,000, with 1,750 hospitalizations and 2 deaths, totaling a cost of 1.5 billion dollars. From 1993 to 1998, 926 outbreaks were reported in 15 European Union (EU) countries (Smyth et al, 2006). In Japan, according to the Ministry of Health and Welfare of Japan, during a period of 20 years (1980–1999), a total of 2,525 outbreaks of staphylococcal food poisoning were reported, which involved 59,964 persons, resulting in three deaths (Alarcon et al, 2006).…”

“…Antibiotic resistance in microbes still remains one of the global major concerns in public health, with methicillin-resistant staphylococci (MRS) strains representing one important group, commonly reffered to as “Super Bugs” (Xu et al, 2011). Since their first discovery in 1961, MRS (including methicillin-resistant S. aureus , MRSA; and methicillin-resistant coagulase-negative staphylococci, MRCNS) has become one group of the most prevalent pathogens causing nosocomial infections throughout the world (Alarcon et al, 2006; Shimizu, 2000; Smyth et al, 2006; Xu et al, 2008a, b). MRS strains show resistance to nearly all β-lactam antibiotics and commonly multiple other drugs due to the mecA and other resistance genes carried by a mobile genetic element, designated staphylococcal cassette chromosome mec (SCC mec ).…”

Factors impacting microbial load of food refrigeration equipment

“…We studied three microbiological indicators of surface hygiene: the aerobic mesophilic counts, presumptive Bacillus cereus and Staphylococcus aureus. The latter two indicators were counted because prevalence studies showed they are the food pathogens most frequently found in refrigeration equipment (Evans, Russell, James, & Corry, 2004;Jackson, Blair, McDowell, Kennedy, & Bolton, 2007;Smyth et al, 2006).…”