MIDTERM 2 - Staphylococcus Flashcards by hhshsjwy, pmmmamnhwg

most important & most commonly encountered organism in medical practice

Genus Staphylococcus

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used to distinguish among Gram-positive cocci

Catalase Test

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ubiquitous human parasite

Genus Staphylococcus

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genus Staphylococcus is catalase-_______-

catalase-positive

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30 – 50% colonize skin & mucous membrane of healthy adult & children

Genus Staphylococcus

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all pathogenic strains of S. aureus are coagulase _____; whereas nonpathogenic species are coagulase _______

pathogenic= positive
nonpathogenic= negative

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genus Streptococcus is catalase-_______

catalase-negative

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enzymes that clot blood by a mechanism that is similar to normal clotting

Coagulase Test

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also known as clumping factor

bound coagulase - Slide Test

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lead to fibrin formation around bacteria, protecting it from phagocytosis

Coagulase

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used to distinguish between pathogenic and nonpathogenic members of the genus
Staphylococcus

Coagulase Test

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cross-links of fibrinogen in plasma to form fibrin clot that deposits on the cell wall

bound coagulase - Slide Test

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individual coccus stick to each other and clumping is observed

bound coagulase - Slide Test

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secreted form of beta lactamase; disrupts the beta-lactam portion of penicillin molecule, thereby inactivating the antibiotic

Penicillinase

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________ are peptides that are mostly secreted by Gram-positive bacteria.

Exotoxins

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= major protein component of cell wall
= major antigenic determinant unique to S. aureus
= protect organism from opsonization and phagocytosis

Protein A

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_______ are lipopolysaccharides (LPS) and is secreted by Gram-negative bacteria

Endotoxins

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_____ is an extracellular enzyme

free coagulase

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Proteins that Disable Host Immune Defenses

Coagulase & Protein A

______ secreted by S.aureus reacts with coagulase reacting factor (CRF) in plasma to form thrombin; converts fibrinogen to fibrin resulting in clotting of plasma

free coagulase

= gram + cocci
= arranged in grape-like clusters
= nonmotile, noncapsulated (mutant strain have capsule & more pathogenic)
= produce lipochrome →golden yellow colonies on blood agar

Staphylococcus aureus

usually affects neonates with local infection of
recently severed umbilicus or older children with skin
infections.

Staphylococcal Scalded Skin Syndrome

also called transpeptidase; necessary for cell wall peptidoglycan formation and is inhibited by penicillin

Penicillin binding protein

diffuse erythematous skin rashes involving entire
body with sloughing off epidermal layer of skin; healing is rapid and mortality low

Staphylococcal Scalded Skin Syndrome

protein that breaks down proteoglycans in connective tissue

Hyaluronidase ("Spreading Factor")

S. aureus establishes a local infection and releases Exfoliatin toxin that exerts distant effects

Staphylococcal Scalded Skin Syndrome

enzyme which degrades fats and oils that often accumulate on the surface of our body. This degradation facilitates Staphylococcus aureus' colonization of sebaceous glands

Lipase

protein that lyses formed fibrin clots

Staphylokinase

destroys tissue proteins

Protease

anti-phagocyti; damage cell membrane of neutrophil & macrophages causing them to lyze; probably help incapacitate the phagocytic line of defense of the host

Leucocidin

no hemolysis; no zones around the colonies

gamma | δ

produce incomplete hemolysis in blood agar; colonies surrounded by a green, opaque zone

alpha | α

causes skin to slough off (scalded skin syndrome)

Exfoliatin | epidermolytic

produce complete hemolysis in blood agar; clear (transparent) zone surrounding the colonies

beta | β

cause food poisoning, resulting in vomiting & diarrhea

Enterotoxins (heat stable)

causes toxic shock syndrome; pyrogenic toxins called superantigens and bind to antigen presenting cells (such as macrophages) causing a massive T cell response and outpouring of cytokines, resulting in the toxic shock syndrome

Toxic Shock Syndrome toxin (TSST-1)

____ is a collection of pus

abscess

deeper infection; tissue becomes hot, red, shiny and swollen

Cellulitis

2nd leading cause of UTI in sexually active young women

Staphylococcus saprophyticus

S. aureus in food produces ________ not inactivated by cooking

Pre-formed, heat resistant toxin

penetrates vaginal mucosa & is a potent stimulator of tumor necrosis factor (TNF) & interleukin-1

Toxic Shock Syndrome

contagious, occurs on the face honey-colored & wet

Impetigo

_____ is an infection deep into the subcutaneous tissue

furuncle

______ are multiple contiguous, painful lesions communicating under the skin

carbuncles

most commonly acquired by females (95%) in the community (NOT in the hospital)

Staphylococcus saprophyticus

white colonies on blood agar; nosocomial & opportunistic infections

Staphylococcus epidermidis

compromised hospital patients with Foley catheters or IV lines can become infected; frequent skin contaminant of blood cultures

Staphylococcus epidermidis