| Term | Definition |
|---|
| Staphylococci | catalase positive; gram-pos; oxidase negative; facultative anaerobes; non-motile; found on skin and mucosal surfaces; S. aureus is the most virulent of the group |
| Micrococci | catalase positive; gram-pos; strict aerobe; modified oxidase; non-motile; found on skin and mucosal surfaces; infections are rare |
| M. luteus | skin, mucosal, nasophyarynx; rare infections; contaminant; virulence factors are unknown; characteristics: small, yellow, shiny colonies, non-hemolytic, sensitive to high-salt, sensitive to low bacitracin |
| Staph epidermidis | catalase positive; gram-pos; large numbers over skin and mucus membranes; can contaminate samples; nosocomial; infections-sepsis from indwelling catheters, endocarditis involving prosthetic heart valves; virulence factors-adhesins that allow for the attachment to medical devices, biofilm formation, & antibiotic resistance |
| Staph saprophyticus | catalase positive; gram-pos; skin and genitourinary tract; endogenous infection UTIs in young and sexually active women; community; virulence factions not well understood; defining characteristics = non-hemolytic, large shiny white colonies, coagulase neg, novobiocin resistant |
| Staph aureus | catalase positive; gram-pos; can colonize in nostrils, nasopharynx, perineal area, skin and mucosa; communtiy and nosocomial; transmission-endogenous, direct, formite, air; characteristics=beta-hemolytic, small to medium, round, shiny, yellowish colonies, coagulase positive. |
| Staph aureus | causes diseases such as: skin infections-boils, folliculitis, impetigo; deep tissue infections-joints, bones, lungs, endocarditis, and sepsis |
| Staph aureus | causes TOXIC SHOCK SYNDROME: confusion, headache, high fever, low BP, diarrhea, seizure, rash, desquamination; it effects all ages-post childbirth, current S. aureus infection, packings (nosebleeds, absorb pus), menstruation/tampon use, barrier contraceptives; 5% death rate |
| Staph aureus | causes Scalded Skin Syndrome-effects young children, causes high fever, dehydration, desquamination, 4% death rate |
| Staph aureus | causes food poisoning: fast acting 1-6 hrs after eating; stomach cramps and diarrhea=mild; dehydration, headache, muscle cramping=severe |
| Staph aureus virulence factors | •adhesins-fibronectin, fibrinogen, collagen; •invasins =tissue destruction: staphylokinase, hyaluronidase; =cell destruction- -alpha-hemolysin: form pores in plasma membrane of some WBCs and erythrocytes; -β-hemolysin:sphingomyelinase, weakens plasma membrane of erythrocytes and monocytes; -Leukocidin: form pores in p.m. of WBCs; =Coagulase: converts fibrinogen to fibrin = clotting; •Phagocytosis inhibition: Capsule-polysaccharide coating; Protein A - binds Fc portion of IgG •Immunological disguises: Protein A, coagulase, clumping factor (binds fibrinogen) |
| Staph aureus toxins | • Exfoliatin (ExfoliativeToxin): cleaves cadherins found in desmosomes in the epidermis. Dead epidermal layer peels off; superantigen •Toxic Shock Syndrome Toxin-1 (TSST-1): Superantigen •Enterotoxin: Superantigen |
| Superantigen | –Bind MHC II molecules on APCs & Vβ chains of TCR; –Cause massive overstimulation of T cells; –IL-1, IL-2, TNF-α, γ-IFN cause the disease; –hypotension, high fever, and diffuse rash |
| Modes of Clinical Testing | •Isolation and Testing on selective or differential media --> ex. SBA, DNase, MSA; •Other tests: ex. catalase, oxidase, Taxo A, novobiocin, coagulase; •Antimicrobial susceptibility testing |
| types of SBA reactions | α-hemolysis-green/brown discoloration; β-hemolysis-complete zone clearing; γ-hemolysis-no clearing at all |
| DNase | differential media used to show if the organism produces DNase |
| Mannitol Salt Agar (MSA) | differential and selective media: tests for salt tolerance and ability to ferment mannitol; •results=no growth, growth+pink=tolerates high salt and there is no mannitol fermentation, growth+yellow=tolerates high salt and ferments mannitol |
| catalase test | 2 H2O2 → 2 H2O + O2 |
| coagulase test | detects cell-associated clumping factor [word] that reacts with fibrinogen; uses rabbit serum on slide, place bacteria on slide--> watch for agglutination. results: clumps=positive, no clumps=negative |
Combine with other sets
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