Bio 315 - Microorganisms and human disease: General...

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Unformatted text preview: Microorganisms and human disease: General Considerations • In general, we want to focus on – Etiology - what pathogen causes a disease – Signs and symptoms – Mechanism of pathogenicity – Communicability – Treatments – Any other interesting or pertinent information • Use cdc.gov as a resource! Bacterial Diseases The Skin • The skin (an organ) is a barrier to microorganisms - it is ofFcially termed the cutaneous membrane of the integumentary system. • The skin consists of: – The epidermis (epithelial tissue Flled and sealed with keratin) – The dermis (which contains sweat and sebaceous glands and hair follicles) – The subcutaneous layer (mostly fat for insulation) • As previously discussed, the skin produces sweat and sebum, which generally inhibit the growth of microorganisms. Normal skin microbiota • Gram-positive cocci (like Staphylococcus epidermidis ) are the most common. Skin lesions: terms • Classifcation • Vesicles are small Fuid flled lesions • Bullae are vesicles larger than 1 cm. • Macules are Fat, reddened lesions • Papules are raised lesions • Pustules are raised lesions containing pus Gram-positive cocci infections • In general, Staphylococcus sp. are common members of the skin microbiota, and usually cause few problems. • They are adapted to the high salt concentrations and potential desiccation that inhibits many bacteria from living on the skin. "Staph" infections • S. epidermidis is makes up > 90% of the normal skin microbiota. • S. aureus , on the other hand, makes up less than 10%, and is usually pathogenic. • S. aureus often produces various toxins (e.g. leukocidins, exfoliative toxin, etc.) • Most strains are penicillin-resistant (due to the production of penicillinases), but are often susceptible to some semi-synthetic penicillins. • S. aureus usually infects the skin by entering a hair follicle. "Staph" infections • This folliculitis often manifests as a “pimple”. • Other manifestations are sties (folliculitis of an eyelash), and boils (a localized inFammation that may become rather large, accompanied by pus). • With all Staph infections, the danger exists that underlying tissue may become infected or that the infection will enter the bloodstream (septicemia), where the circulation of toxins may cause toxemia. Basic folliculitis A boil "Staph" toxemias • Scalded skin syndrome is a disease in which sheets of skin actually peel off when touched - this isn't good. It is caused by the production of an exfoliative toxin by the bacterium. • Toxic shock syndrome is a particularly dangerous condition caused by TSST-1, and causes fever, vomiting, rash, and shock - it may be fatal. It was originally associated with the use of a new type of tampon left in place too long that provided favorable growth conditions for the pathogens. Scalded Skin Syndrome Streptococcal infections • Different species and strains of Streptococcus are classiFed according to their hemolytic enzymes...
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This note was uploaded on 07/04/2010 for the course BIO 315 taught by Professor Schmidt during the Spring '08 term at SUNY Stony Brook.

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Bio 315 - Microorganisms and human disease: General...

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