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FORMAT FOR THE STUDY OF
MICROORGANISMS
- Identification / Taxonomy / Physical Characteristics2. Epidemiology3. Virulence Factors4. Host Defense Mechanisms5. Clinical Manifestations of Disease6. Prevention / Treatment TERM 2
. Identification / Taxonomy / Physical
Characteristics
DEFINITION 2 Gram stain & cell morphologymetabolic characteristics of growth antigenic composition TERM 3
Epidemiology
DEFINITION 3 natural host or habitatmode of transmission TERM 4
Virulence Factors
DEFINITION 4 cellular componentsenzymestoxins TERM 5
Prevention / Treatment
DEFINITION 5 risk factorsvaccinesantimicrobial drugsdevelopment of resistance
Staphylococcus
Characteristics Gram-positive cocci in grape-like clusters facultative catalase positiveFacultative can grow in either aerobic or anerobic conditionsCatalase test differentiates between strep and staph TERM 7
Staphylococcus - identification / classification
DEFINITION 7 Facultative Gram Positive Cocci | | CATALASE |Negative----------- ----- --------Positive | | Streptococcus Staphylococcus | COAGULASE | Positive----------- --------------Negative | | | | Staphylococcus aureus Staphylococcus epidermidis TERM 8
Catalase Test
DEFINITION 8 catalase2H2O2 -------------------------> 2H2O + O2 (bubbles) Catalase detoxifies H2O2Place hydrogen peroxide on the plate, add catalase, if positive then there will be bubbling TERM 9
Coagulase test
DEFINITION 9 coagulase fibrinogen ----------------------> fibrin clotAn enzyme produced by Staphylococcus aureus that causes fibrin clot formation TERM 10
Other Characteristics of Staphylococcus
aureus
DEFINITION 10 Phenol red mannitol salts agar selective differential media for S. aureus salt resistant growthmannitol fermentation yellow color changeBlood agar plateB-hemolytic
Virulence factors of Staphylococcus aureus
Normally Fab2 region of antibody binds to antigen, Protein Abinds the Fc region of antibody, so antibody is bound backwardand does not mediate normal protective function(s) TERM 17
Important Virulence Factors
DEFINITION 17
- coagulase - cloak w/ fibrin - retard immune response - activity linked to invasive potential- hemolysins & leucocidins (-toxin is both) - exfoliatin - protease cleaves desmosomesshedding of epidermidis - enterotoxins (including toxic shock syndrome toxin)
- 8 immunologic types / A-H / F is TSST act as superantigens stimulate release of IL-2 & IL-6 from T-cells & IL-1 & TNF from macrophages TERM 18
Inflammatory Manifestations
DEFINITION 18 Skin infections abscess formation (almost any anatomical site) folliculitis hair follicle boil (furuncle) sebaceous gland involvement carbuncle confluent boils impetigo superficial, localized cellulitis subcutaneous, usually diffuse Wound infections ~25% of burn wound infections ~15 - 20% of post- operative wound infections (1-10% of post-operative wounds become infected)) TERM 19
abscess
DEFINITION 19 collection of pus in any part of the body that,in most cases, causes swelling and inflammation around it follicultitis boil/furuncle carbuncle TERM 20
Staphylococcal skin infections
DEFINITION 20 Impetigo Cellulitis - frequently located on limbs but may be anywhere
Inflammatory Manifestations -
Otitis media (2nd most common cause)Sinusitis (both acute & chronic) Systemic infections bacteremia/septicemia (~10-40% fatality) - metastatic abscesses endocarditis (~30 % of all cases) osteomyelitis (most common cause) septic arthritis (most common cause) Pneumonia TERM 22
Toxin-mediated Manifestations
DEFINITION 22 (1) scalded skin syndrome - infants/children (& adults) caused by exfoliatin (2) food poisoning most common cause of bacterial food poisoning in USAsymptoms appear 2- hours after eating foodfood contains preformed toxin ~ 1 g (100,000 S. aureus / gram)the toxin is relatively heat stable TERM 23
Toxin-mediated Manifestations -continued
DEFINITION 23 (3) toxic-shock syndrome fever, headache, muscle pain, vomiting, diarrhearapid breathing, tachycardia, hypotensionskin rash & desquamationdysfunction of several organ systems usually superficial or focal infection - negative blood culture TERM 24
Staphylococcal Toxic Shock Syndrome
DEFINITION 24 ~5-25% of S. aureus strains produce exotoxin F (TSST) ~90% individuals seropositive in adulthood 1978 - TOXIC SHOCK SYNDROME menstruating women / tampon usageNow~ 50% cases nonmenstrual (both women & men) TERM 25
Staphylococcal superantigen(s)
DEFINITION 25 Normal antigen activates Superantigen activates ~ 0.01% of T-cells ~5-20% of T-cells Result large amounts of Il-1, Il-2, & TNF released
