_aureus Mississippi University for 金黄色葡萄球菌密西西比大学课件.ppt

Staphylococcus aureus Food Poisoning St. aureus and food poisoning St. aureus causes gastro-enteritis Food poisoning is not caused by the organism but by the toxin that the organism secretes St. aureus food poisoning is the most common form of food poisoning in the US Properties of Staphylococcus aureus Gram positive cocci arranged in grape like clusters Non-sporulating Colonies on TSA are small, creamy and golden colored Colonies on MSA are yellow and turns the media yellow Properties of St. aureus that make it persistent in nature Relatively heat resistant Resistant to high concentrations of salt Can survive long periods on dry inanimate objects 2 Case Studies What were the symptoms of food poisoning? How did the chefs contaminate the food? How did the chef get a staph infection? How did the chef get a staph infection? Staph is found on any inanimate surface Staph is often found associated with the external nares of 30% of the human population Staph is often found on skin surfaces because they can tolerate the low moisture and high salt content of skin Staph can easily spread from person to person via hand to hand contact Staph can penetrate the deep tissues of skin damaged by burns cuts insect bites skin diseases—acne, psoriasis, eczema What happens when Staph enters a wound and how does this relate to food poisoning ? Localized staph infection leading to an abscess (collection of pus) boils=abscesses in the skin carbuncle=interconnected abscesses Rupture of the abscess leads to the release of live bacteria and associated toxin How do abscesses and boils form? Chef cuts arm and Staph enters deeper skin layer St. aureus is surrounded by a capsule thick slime layer that prevents an immediate immune response Bacteria multiply at the site surrounded by the capsule St. aureus establishes intimate contact with skin cells via bacterial techoic acids and fibronectin skin cell receptors Abscess and boil formation (cont’d) St. aureus produces coagulase