Strep pyogenes Flashcards
(15 cards)
1
Q
General
A
- Colonize Nasopharynx or Skin
- Asymptomatic carriage common in children
- Lancefield Group A
2
Q
Morphology
A
- Gram-Positive
- Cocci
- Long Chains
- Encapsulated (H.A)
- B-Hemolytic
3
Q
Cultivation
A
- Fastidious
- Blood agar + 5% CO2
4
Q
Non-toxic Virulence Factors
A
- H.A Capsule, non antigenic
- M-Protein (antigenic mimicry)
- F-Protein, both adhesins
- Streptokinase (plasmin act., fibrinolysis)
- DNAse
- Hyaluronidase
- C5a peptidase (prevents opsonization)
5
Q
Toxic Virulence Factors
A
- Streptolysin: Lysis of RBC/WBC
- Streptolysin O: B-hemolysis
- Streptococcal Pyrogenic Exotoxins (SPEs) superantigens
6
Q
Streptococcal Pyrogenic Exotoxins (SPEs)
A
- SPE-A / C: Scarlet fever, TSST-like
- SPE-B: Necrotizing Fasciitis
7
Q
Respiratory Diseases
A
- Pharyngitis (strep)
- Tonsillitis Follicularis
- Sinusitis & Otitis media
8
Q
Skin Diseases
A
- Impetigo
- Erysipelas (most common)
- Cellulitis
- Necrotizing Fasciitis
9
Q
Erysipelas
A
Inflammation of Dermis & large red inflamed area with sharp edge & fever
10
Q
Toxin-mediated Diseases
A
- Scarlet Fever
- Streptococcal TSS (more lethal than staph aureus)
11
Q
Post-Streptococcal Diseases
A
1-5 weeks after due to immune resp.
- Acute Rheumatic Fever
- Acute Glomerulonephritis
- Rheumatoid Arthritis
12
Q
Acute Rheumatic Fever
A
- Molecular mimicry of M-protein
- Similar to Cardiac Myosin
- Endo/Myo/Peri-carditis = Pancarditis
- JONES criteria: Joints, Heart, Nodules, Erythema marginatum, Sydenham/s Chorea (jerking)
13
Q
Acute Glomerulonephritis
A
- Type II hypersensitivity reaction
- Antigen-Antibody complexes deposit in glomeruli
- Triggered inflammation
- Edema, Hypertension, Hematuria, Proteinuria
14
Q
Treatment
A
Penicillin
(Macrolides if allergic - erythromycin)
15
Q
Microbiological Diagnosis
A
- Catalase Negative
- Bacitracin Sensitive
- CAMP Negative
- ASO-titer (anti-streptolysin-O)
