Staphylococcus aureus and Staphylococcal enterotoxins in foodborne diseases

Abstract

ABSTRACT. Staphylococcal food poisoning (SFP) is one of the most significant foodborne diseases. It is a mild intoxication, which is caused by the ingestion of food containing one or more preformed staphylococcal enterotoxins (SEs). The toxic dose of SEs in human is usually ranged from 20 ng to 1 μg. SEs are proteins produced by Staphylococcus spp in various parts of the environment, including foods. Although several staphylococci can produce SEs, the majority of SFP cases is attributed to S. aureus. Traditionally, five antigenic SE types have been recognized: SEA, SEB, SEC, SED and SEE. During the 1990's, new SEs (SEG, SEH, SEI and SEJ) were reported and their genes were described. Several studies revealed that SEH, SEG and SEI were, also, involved in the gastroenteric syndrome. More recent data have indicated the presence of "new" SE genes and new SEs, designated as "staphylococcal enterotoxin-like" (SEI). The role of SEI in food poisoning has not yet been clarified. In contrast to S. aureus, SEs are remarkably heat resistant (D-values of 3-8 min at 121 ° C). They may be present in foods even when viable cells of S. aureus are absent. The enterotoxins are, also, resistant to proteolytic enzymes. It is generally accepted that toxic levels of SEs are produced in foods when S. aureus concentration exceeds 10 5 cfu/ml. S. aureus can grow at a temperature range of 7-48.5°C, with optimum 30-37°C, a pH range of 4.2-9.3, with optimum 7-7.5, minimum a w of 0.86, and up to 15% NaCl. SEs can be produced at a temperature range of 10-46 ° C, with optimum 40-45 ° C, a pH range of 4.8-9.0, with optimum 5.3-7.0, and a w range of 0.86-0.99, with optimum 0.90. Among the foods implicated in SFP are usually milk, dairy products and meat. SEA and SED are usually identified in foodborne outbreaks, while SEC is an important cause of SFP associated with the consumption of dairy products. The European regulation has set criteria for presence of SEs in cheeses, milk powder and whey powder (Regulation EC, 2073. If population of coagulase-positive staphylococci in samples exceeds 10 5 cfu/g, these samples should be further tested for the presence of SEs. In this case, SEs must not be detected in 25 g of the products. ΠΕΡΙΛΗΨΗ. Η σταφυλοκοκκική τοξινωση (ΣΤ) είναι ένα από τα πιο συχνά αίτια τροφιμογενοΰς νόσου. Είναι μιατοξίνωση που προκαλείται από την πρόσληψη με τα τρόφιμα μίας ή περισσοτέρων προσχηματισμένων σταφυλοκοκκικών εντεροτοξινών (ΣΕ). Οι τοξικές δόσεις των ΣΕ για τον άνθρωπο κυμαίνονται από 20 ng έως 1 μg. Οι ΣΕ είναι πρωτεΐνες που παράγονται από ορισμένα είδη σταφυλόκοκκων τόσο στο περιβάλλον όσο και στα τρόφιμα. Παρόλο που διάφορα είδη σταφυλόκοκκου μπορούν να προκαλέσουν τροφιμογενείς λοιμώξεις, σχεδόν όλα τα περιστατικά ΣΤ αποδίδονται στο S. aureus. Παραδοσιακά έχουν αναγνωριστεί οι κλασικοί τύποι σταφυλοκοκκικών εντεροτοξινών SEA, SEB, SEC, SED και SEE. Στη δεκαετία του 1990 ανι χνεύτηκαν νέες τοξίνες (SEG, SEH, SEI, SEJ) και προσδιορίστηκαν τα γονίδια που ελέγχουν την παραγωγή τους. Πιο πρόσφατα στοιχεία οδήγησαν στον πρ...

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