University:
Eastern Kentucky University
Course:
BIO 273 | Clinical Microbiology
Academic year:

2022
Views:

102

Pages:

3
Author:

rezancuk2j

Strep Pyogenes (+) (GROUP A STREP) Features: 1. Catalase negative 2. Encapsulated a. Hyaluronic acid in capsule 3. Beta hemolytic 4. Bacitracin sensitive Pathogenesis: 1. M protein a. Virulence factor for Rheumatic fever and Post streptococcal glomerulonephritis 2. Hyaluronic acid a. Not immunogenic 3. Streptococcal pyogenic exotoxin (SPE) a. SPE A, C: Scarlett fever, Toxic shock-like syndrome (TSLS) b. SPE B: Necrotizing fasciitis 4. Streptolysin O a. Hemolysin b. ASO antibodies (ASO titer) 5. Streptokinase a. Converts plasminogen to plasmin b. Breaks fibrin clots c. Spreading factor 6. DNAse Diseases: Divided into as follows: Impetigo Pyogenic Infections Pharyngitis Diseases Cellulitis/Erysiplas Scarlet Fever Caused by SPE TSLS Necrotizing Fascitis Rheumatic Fever Sequelae PSGN Pyogenic Infections: 1. Pharyngitis 2. Impetigo a. Honey-crusted lesions on skin 3. Cellulitis 4. Erysiplas a. Superficial cellulitis with well-demarcated borders b. Most common cause Caused by SPE: 1. Scarlet Fever a. Strawberry tongue b. Widespread rash that spares face 2. TSLS a. Superantigen 3. Necrotizing Fascitis a. Caused by SPE B b. Surgical emergency c. Sometimes amputation done Sequelae: 1. Rheumatic fever 2. PSGN Rheumatic Fever: 1. M protein (main virulence factor) a. Interferes opsonization (inhibits phagocytosis) b. Very antigenic i. Leads to immune response ii. Antibodies made against self antigens iii. The self antigen is in myosin in muscles iv. Hence, affecting heart (mitral valve) v. This process is called molecular mimicry c. If pharyngitis is immediately treated, RF doesn’t occur. d. Symptoms (JONES): i. Joints: Polyarthritis ii. : Valvular damage, myocarditis, pericarditis. iii. Nodules: Subcutaneous iv. Erythema Marginatum: Rash with thick borders v. Sydenham’s chorea: Involuntary movement of hands and face Post Streptococcal Glomerulonephritis: 2. M12 serotype 3. Symptoms: a. Dark brown (cola colored) urine b. Facial edema 4. Occurs 2 weeks after streptococcal infection Differences between RF and PSGN Rheumatic Fever PSGN  Occurs after pharyngitis   Doesn’t occur if pharyngitis is treated  Treatment: 1. Penicillin (Beta lactam drugs) Can occur after pharyngitis or any other superficial infection like impetigo Occurs, no matter if the strep infection is treated or not