Gram-Positive Cocci Flashcards

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1
Q

Staphylococcus: Genus Characteristics

A
  • Gram-positive cocci
  • Grape-like clusters
  • Catalase positive
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2
Q

Staphylococcus Aureus : Species Characteristics

A

Coagulase positive • Golden colonies on blood agar • β - hemolytic • Ferments mannitol on mannitol salt agar

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3
Q

Staphylococcus Aureus: Reservoir

A

Normal flora, nose and skin

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4
Q

Staphylococcus Aureus : Transmission

A

• Hands • Sneezing • Surgical wounds • Contaminated food

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5
Q

Staphylococcus Aureus: Predisposing Factors

A

• Breaks in skin • Foreign body • Neutropenia • Intravenous drug abuse • Chronic granulomatous disease • Cystic fibrosis

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6
Q

Staphylococcus Aureus : Pathogenic Features

A

• Coagulase: Converts fibrinogen to fibrin • Alpha Toxin : Pore-forming, cytolytic toxin • Protein A: Inhibits IgG opsonization by binding Fc component • Enterotoxins: Fast acting, heat stable • Toxic Shock Syndrome Toxin-1 (TSST-1): Acts as superantigen • Exfoliatins: Proteases specific for cadherin desmoglein 1, promote epidermal blistering of scalded skin syndrome and bullous impetigo

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7
Q

Clinical Syndromes of S. aureus: Food poisoning

A

3-6 hours onset, salty foods, picnics (ham, canned meats, custard pastries, potato salad) Pathogenesis: Enterotoxlns A·E, preformed In food, heat stable

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8
Q

Clinical Syndromes of S. aureus: Infective endocarditis

A

Acute onset, fever. malaise, leukocytosis, heart murmur Pathogenesis: Coagulase, cytolytic toxins

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9
Q

Clinical Syndromes of S. aureus: Pneumonia

A

Typical pneumonia, salmon·colored sputum, nosocomial, ventilator. postinfluenza, high fatality Pathogenesis: Coagulase, cytolytic toxins

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10
Q

Clinical Syndromes of S. aureus: Osteomyelitis (No. 1 cause overall)

A

Bone Pain, fever, swelling, redness, lytic lesions on imaging Pathogenesis: Coagulase, cytolytic toxins

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11
Q

Clinical Syndromes of S. aureus: Surgical Infections

A

Fever. cellulitis, abscess Pathogenesis: Coagulase, oxfollaUns. TSST

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12
Q

Clinical Syndromes of S. aureus: Mastitis

A

Subcutaneous tenderness, heat, redness Pathogenesis: Coagulase cytolyslns

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13
Q

Clinical Syndromes of S. aureus: lmpetigo

A

Erythematous papules and bullae

Pathogenesis: Coagulase, exfollatlns

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14
Q

Clinical Syndromes of S. aureus: Scalded skin syndrome

A

Dlffuse epidermal peeling

Pathogenesis: Coagulase, exfollatlns

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15
Q

Clinical Syndromes of S. aureus: Toxic shock syndrome

A

Scarlatiniform: rash desquamates, involves palms and soles, fever, hypotension, multi-organ failure Pathogenesis: TSST-1 (superantigen)

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16
Q

Treatment of S. aureus

A

Gastroenteritis: Self -limiting

Nafcillin/oxacillin

Methicillin -resistant Staphylococcus aureus (MRSA): vancomycin

Vancomycin-resistant (VRSA) or vancomycin -intermediate (VISA): Qulnupristin / dalfoprlstin

17
Q

Staphylococcus epidermidis: Species Characteristics

A

Coagulase-negative Staphylococcus

Gamma hemolytic

Novobiocin sensitive

18
Q

Staphylococcus epidermidis: Pathogenic Features

A

• Biofilm production

Normal flora of skin

19
Q

Staphylococcus epidermidis: Clinical Syndromes

A

• Subacute endocarditis in IV drug users

Infections of catheters and prosthetic devices

20
Q

Staphylococcus epidermidis: Treatment

A

Vancomycin with rifampin or an aminoglycoside

21
Q

Staphylococcus saprophyticus: Species Characteristics

A

Coagulase-negative Staphylococcus

Gamma hemolytic

Novobiocin resistant

22
Q

Staphylococcus saprophyticus: Clinical Syndromes

A

Honeymoon cystitis

23
Q

Staphylococcus saprophyticus: Treatment

A

Quinolones

24
Q

Streptococcus: Genus Characteristics

A

Gram-positive cocci

Chains or pairs

Catalase negative

25
Q

Streptococcus: Further Classification

A

The genus Streptococcus Is divided into groups by classification of a cell wall carbohydrate (C carbohydrate). Analysis with this technique separates four medically Important groups: A, B, D, and those that are “ non-groupable” because they lack this carbohydrate. In clinical microbiology, we distinguish the streptococci on the basis of their patterns of hemolysis and associate that result with our knowledge of the four Lancefleld groups.

26
Q

β- Hemolytic Streptococci Group A Streptococcus (GAS; Streptococcus pyogenes): Species Characteristics

A

β-hemolytic

Bacitracin sensitive

Pyrrolidonyl arylamidase (PYR) positive

Type with M protein

27
Q

β- Hemolytic Streptococci Group A Streptococcus (GAS; Streptococcus pyogenes): Reservoir

A

Throat and skin

28
Q

β- Hemolytic Streptococci Group A Streptococcus (GAS; Streptococcus pyogenes): Transmission

A

Respiratory droplets, direct contact

29
Q

β- Hemolytic Streptococci Pathogenic Features of S. pyogenes

Surface features: Pili and teichoic acids

A
30
Q

β- Hemolytic Streptococci Pathogenic Features of S. pyogenes:

Soluble secretions

A
31
Q

β- Hemolytic Streptococci Pathogenic Features of S. pyogenes:

Spreading factors

A
32
Q
A