Gram Positive Cocci - Staphylococci

General characteristics of Staphylococci include:

facultative anaerobes, halophiles, have strong positive catalase reaction, appears as gram positive cocci in clusters

Species of staph associated with human disease include:

S. aureus, S. epidermitis, S saprophyticus, S. lugdunensis, and S. haemolyticus

S. aureus

the major cause of nosocomial infections; beta hemolytic(clear); creates bio films

_________ determines pathogenicity in Staph

Coagulase

Coagulase

only produces by S.aureus; causes blood to clot by activating the conversion of fibrinongen to fibrin

Mannitol Salt Agar

contains a high salt concentration making it selective; also contains mannitol and indicator phenol red making it differential

Mannitol salt agar makes S. aureus appear______ and other Staphylococci don’t change the agar

yellow

Endotoxin

The lipid A component present in the cell wall of gram negative bacteria; releases upon cell death

Exotoxins

highly toxic proteins actively secreted by healthy bacteria (GP and GN)

Types of exotoxins include:

neurotoxins, enterotoxins, and cytotoxins

Neuron toxins

works on neurons

Enterotoxins

works on the enteric tract; causes GI symptoms

Cytotoxins

destroys cells/entire tissues

How does S.aureus cause food poisoning?

When food is contaminated by worker with staphylococci on hands and then sits at room temperature, the organisms incubate in the food and releases toxins

Staph can cause the following skin diseases:

scalded skin syndrome, impetigo, abscesses, folliculitis, sty, furuncles/carbuncles

Scalded Skin Syndrome (SSSS)

caused by exfoliative toxin

Impetigo

similar to SSSS but produces puss that contains bacteria and WBC; seen in children

Folliculitis

an infection of hair follicle; can turn into a sty if it occurs on eye;

Furuncle/Carbuncle

Boil/ when furuncles join together

Toxic Shock Syndrome is caused by:

TSS toxin type 1, Strep Group A and staphylococcal enterotoxin B

Toxic Shock Syndrome

causes fever, vomiting, sunburn like rash, and vascular collapse