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56 Cards in this Set
- Front
- Back
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Where are Staphylococci commonly found?
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Common inhabitants of the skin and mucous membranes
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How are Staph. cells arranged?
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spherical cells arranged in irregular clusters
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Is Staph. gram positive or gram negative?
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Gram-positive
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What structures do staph. lack?
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spores and flagella
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Can staph cells be capsulated?
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yes, but not always
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How does S. aureus grow?
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grows in large, round, opaque colonies
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characteristics of S. aureus
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facultative anaerobe; w/stands high salt, extemes in pH, and high temperatures; produces many virulence factors
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Where is S. aureus carried?
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nasopharynx and skin
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What are the enzymes produced by S. aureus?
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Coagulase, Hyaluronidase, Staphylokinase, DNase, Lipases, Penicillinase
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enzyme that coagulates plasma and blood; produced by 97% of human isolates; diagnostic
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coagulase
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enzyme that digests connective tissue
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Hyaluronidase
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enzyme that digests blood clots
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Staphylokinase
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enzyme that digests DNA
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DNase
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enzyme that inactivates penicillin
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Penicillinase
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Toxins produced by S. aureus
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Hemolysins, Leukocidin, Enterotoxin, Exfoliative toxin, Toxic Shock syndrom toxin (TSST)
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toxin that lyses red blood cells (alpha, beta, gamma, delta)
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Hemolysins
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toxin that lyses neutrophils and macrophages
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Leukocydin
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toxin that induces gastrointestinal distress
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enterotoxin
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toxin that separates the epidermis from the dermis
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exfoliative toxin
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toxin that induces fever, vomiting, shock, systemic organ damage
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Toxic shock syndrome toxin
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Is S. aureus present in most environments frequented by humans?
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yes
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How are people predisposed to S. aureus infections?
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poor hygiene and nutrition, tissue injury, preexisting primary infection, diabetes, immunodeficiency
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What are the localized cutaneous infections caused by S. aureus?
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folliculitis, furuncle, carbuncle, impetigo
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localized cutaneous infection that causes superficial inflammation of hair follicle; usually resolved with no complications but can progress
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folliculitis
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localized cutaneous infection that causes a boil; inflammation of hair follicle or sebaceous gland progresses into abscess or pustule
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furuncle
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localized cutaneous infection that causes a larger and deeper lesion created by aggregation and interconnection of a cluster of furnuncles
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carbuncle
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localized cutaneous infection that causes bubble-like swellings that can break and peel away; most common in newborns
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impetigo
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What are the sytemic infections caused by S. aureus?
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osteomyelitis & bacteremia
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systemic infection that is established in the metaphysis; absess forms
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osteomyelitis
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systemic infection in which the primary origin is bacteria from another infected site or medical devices; endocarditis possible
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bacteremia
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What are the toxigenic diseases caused by S. aureus?
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food intoxication, staphyloccal scalded skin syndrome, toxic shock syndrome
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toxigenic disease caused by ingestion of heat stable enterotoxins; causes gastrointestinal distress
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food intoxication
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toxigenic disease in which the toxin induces bright red flush, blisters, then desquamation of the epidermis
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staphyloccal scalded skin syndrome
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toxigenic disease in which the toxemia leads to shock and organ failure
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toxic shock syndrome
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How is Staph identified in samples?
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frequently isolated from pus, tissue exudates, sputum, urine, and blood
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What do 95% of Staphylocci have?
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penicillinase and are resistant to penicillin and ampicillin
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What is MRSA?
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Methicillin-resistant S. aureus
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What do systemic staph infections require?
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intensive lengthy therapy
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How are staph infections prevented?
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universal precautions by healthcare providers to prevent nosocomial infections; hygiene and cleansing
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Gram-positive spherical/ovoid cocci arranged in long chains; commonly in pairs
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Streptococci
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Are streptococci spore-forming?
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No; are non-spore-forming, nonmotile
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Can Streptococci form capsules and slime layers?
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yes
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Are Streptococci facultative anaerobes?
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yes
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Do streptococci form catalase?
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do not form catalase, but have a peroxidase system
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most parasitic forms are fastidious and require enriched media
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streptococci
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What does Strep colonies look like?
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small, nonpigmented colonies
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What are strep sensitive to?
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drying, heat, and disinfectants
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What is the Lancefield classification system?
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Streptococci classification system based on cell walls
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What are the human streptococcal pathogens?
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S. pyogenes, S. agalactiae, Viridans streptococci, S. pnuemoniae, Eneterococcus faecalis
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the most serious streptococcal pathogen; strict parasite; inhabits throat, nasopharynx, occasionally skin
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Beta-hemolytic S. pyogenes
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C-carbohydrates- protects against lysosomes
Fimbriae- adherence M-protein- contributes to resistance to phagocytosis Hyaluronic acid capsule- provokes no immune response |
surface antigens (virulence factors) produced by
Beta-hemolytic S. pyogenes |
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What are the extracellular toxins produced by Beta-hemolytic S. pyogenes?
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streptolysins, pyogenic toxin (eryhtorogenic), superantigens
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extracellular toxins that cause cell and tissue injury
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streptolysins
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extracellular toxins that induce fever and typical red rash
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pyogenic toxin
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extracellular toxins that are strong monocyte and lymphocyte stimulants; cause the release of tissue necrotic factor
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superantigens
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What are the extracellular enzymes produced by Beta-hemolytic S. pyogenes?
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streptokinase, hyaluronidase, DNase
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