Please enable JavaScript.
Coggle requires JavaScript to display documents.
Genus Staphylococcus (S. aureus
-Grows in large, round opaque colonies…
Genus Staphylococcus
S. aureus
-Grows in large, round opaque colonies
-The only coagulase-positive & species of Staphylococcus
-Also the only primary pathogen
-Optimal temp. = 37 Celsius
-Withstands high salt, extremes in pH + high temperatures
-Carried in nasopharynx & skin
Virulence Factors
Enzymes
-Coagulase: Coagulates plasma & blood; produced by 97% of human isolates; is diagnostic of all Staph infections
-Hyaluronidaise: Digests connective tissue
-Staphylokinase: Digests blood clots
-DNase: Digests DNA
-Lipase: Digests oils + enhances colonization of skin
-Penicillinase: Inactivates penicillin
Toxins
-Hemolysins (alpha, beta, delta & gamma): Lyse RBCs; alpha = most powerful
-Leukocidin: Lyses neutrophils & macrophages
-Enterotoxin: Induces GI distress
-Exfoliative Toxin: Separates epidermis from dermis
-Toxic Shock Syndrome Toxin (TSST): Induces fever, vomiting, shock & systemic organ damage
Epidemiology & Pathogenesis -Present in most environments populated by humans-Readily isolated from fomites-Carriage rate for healthy adults is 20-60%-Mostly carried in anterior nares, skin, nasopharynx & intestine-Predispositions include:
- Poor hygiene & nutrition
- Tissue injury
- Pre-existing primary infection
- Diabetes
- Immunodeficiency
-Resistant to methicillin = Higher difficulty in destruction
Toxigenic Disease
-Food Intoxication: Ingestion of heat stable enterotoxins; causes GI distress
-Staphylococcal Scalded Skin Syndrome: Toxin induces bright red flush, blisters, then desquamation of the epidermis
-Toxic Shock Syndrome: Toxemia leading to shock & organ failure
Systemic Infections
-Osteomyelitis: Infection established in the metaphysis (narrow portion of long bones); forms an abscess; symptoms include fever, chills pain & muscle spasm
-Bacteremia: Primary origin is bacteria from another infected site/contaminated medical equipment; can cause endocarditis
Local Infections -occurs through invasion of the skin through wounds, follicles or glands
-Folliculitis: Superficial inflammation of hair follicles; can usually be resolved w/o complications, but can progress
-Furuncle: Boils; inflammation of hair follicle/sebaceous gland that progresses into abcess/pustule
-Carbuncle: Larger & deeper lesion created by aggregation & interconnection of a cluster of furuncles
-Impetigo: Bubble-like swellings that can break & peel away; common in newborns
Coagulase-Negative
-Are frequently involved in nosocomial & opportunistic infections
-None are primary pathogens
-
3. S. capitis
-Lives on the scalp, face & external ear
1. S. epidermidis
-Lives on skin & mucous membranes
-Causes endocarditis, bacteremia & UTI
4. S. saprophyticus
-Infrequently lives on skin, intestines & vagina
-Causes UTIs
-Almost exclusively found in sexually-active adolescent females
General Characteristics
-Common inhabitant of skin & mucous membranes
-Anaerobic metabolism
-Are spherical cells arranged in irregular clusters
-Gram- & Catalase-Positive
-Lack spores & flagella
-May have capsules
-31 species total, 3 pathogenic species are S. aureus, S. epidermidis & S. saprophyticus
Identification
-Frequently isolated from pus, tissue exudates, sputum, urine & blood
-Also isolated through cultivation, biochemical testing, & catalase-/coagulase-tests
Clinical Concerns & Treatment -
95% have penicillinase, therefore resistant to penicillin & ampicillin
-MRSA (methicillin-resistant S. aureus) carry multiple resistances
-Abscesses have to be surgically perforated
-Systemic infections need long, intensive therapy
Prevention
-Adherence to universal precautions by HCPs to prevent nosocomial infections
-Proper hygiene, cleansing & aseptic techniques
-
-