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Some Staphylococcus aureus strains are able to produce staphylococcal enterotoxins (SEs) which are the causative agents of staphylococcal food poisoning. Foods that are frequently contaminated with S. aureus include meat and meat products, poultry and egg products, salads (e.g. egg, tuna, chicken, potato, and macaroni), bakery products (e.g. cream-filled pastries, cream pies, and chocolate éclairs), sandwich fillings, and milk and dairy products.
Merck offers a considerable selection of products for the enrichment, detection and isolation of Staphylococcus aureus. The range includes dehydrated culture media in a unique and user-friendly granulated format meeting the highest industry standards for performance as set out in ISO 11133.
| Method | ISO 6888 | FDA-BAM Chapter 12 |
|---|---|---|
| Enrichment (MPN) |
Modified Giolitti and Cantoni Broth, |
TSB + 10% NaCl + 1% Sodium Pyruvate |
| Isolation (MPN) and/or direct plate countIsolation (MPN) and/or direct plate count |
Baird-Parker Agar or Rabbit Plasma Fibrinogen Agar, |
Baird-Parker Agar |
| Confirmation | Rabbit Coagulase Test | Rabbit Coagulase Test |
MPN = most probable number
| Procedure step | Product description | ISO 6888 | BAM Ch. 12 |
|---|---|---|---|
| Enrichment | Giolitti-Cantoni Broth |  |
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| Potassium tellurite trihydrate | |
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| Paraffin, viscous | |
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| TSB | |
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| Sodium Chloride | |
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| Sodium Pyruvate | |
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| Isolation/ confirmation |
Baird-Parker Agar (Base) | |
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| Mannitol Salt Agar - LI 30 ml | |||
| Egg Yolk-Tellurite Emulsion | |
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| Brain Heart Broth | |
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| Bactident® Coagulase | |
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Staphylococcus aureus is a facultative anaerobic Gram-positive coccus, which is non-motile, and catalase and coagulase positive. Some S. aureus strains are able to produce staphylococcal enterotoxins (SEs) and are the causative agents of staphylococcal food poisoning. Staphylococci exist in air, dust, sewage, water, milk, and food, as well as on food equipment, environmental surfaces, humans, and animals. Of these, humans and animals are the primary reservoirs. Staphylococci are present in nasal passages as well as throats and on the hair and skin of 50 percent or more of healthy individuals.
Staphylococcus aureus is able to grow in a wide range of temperatures (7–48.5°C, with an optimum of 30–37°C), pH (4.2 to 9.3, with an optimum of 7–7.5) and sodium chloride concentrations (up to 15% NaCl). These characteristics enable S. aureus to grow in a wide variety of foods.
Foods that are frequently incriminated in staphylococcal food poisoning include meat and meat products, poultry and egg products, salads (e.g. egg, tuna, chicken, potato, and macaroni), bakery products (e.g. cream-filled pastries, cream pies, and chocolate éclairs), sandwich fillings, and milk and dairy products. Foods that require considerable handling during preparation and are kept at slightly elevated temperatures after preparation are frequently involved in staphylococcal food poisoning.
The cause of the illness is preformed toxins, and it is therefore characterized by a very short incubation time – typically from 0.5–6 hours, depending on the general health of the victim, susceptibility to the toxin, the concentration of toxin, and the amount of food ingested. The infective dose may be less than 1.0 microgram, which is equivalent to 100000 cfu/g.
The most common symptoms of Staphylococcus infection are nausea, vomiting, retching, abdominal cramping, and diarrhea. Recovery typically takes 1–3 days, but in severe cases complete recovery may take longer. The illness is not transmissible and does not normally require treatment beyond rest and plenty of fluids.
