L37 Flashcards
(34 cards)
What is the universal property of steptococcus?
GP cocci - pairs or cocci
Catalase NEGATIVE
Which strep is group A, beta hemolytic?
S. pyogenes
Which strep is group B, beta hemolytic?
S. agalactiae
What 4 infections are you thinking about with strep pyogenes?
Pus forming: 1. Pharyngitis = strep throat! 2. Skin infections Non-pus: 3. Rheumatic fever 4. Glomerulonephritis
What virulence factor is particularly important for strep pyogenes? (baker’s hat)
M protein
- Inhibits alternative complement
- But… elicits opsonic Abs
- Adhesion to keratinocytes (skin infections)
- *Many different types - you need to have immunity to that specific epitope
How does M protein contribute to rheumatic heart disease?
Abs made against M protein are auto-reactive to heart muscle
Describe other virulence factors notable for s.pyogenes.
- GP capsule = anti-phagocytic
- Surface adhesion molecules
- Toxins
Which hemolysin toxin released by s.pyogenes is tested for recent infection?
Streptolysin O titer
Abs vs this indicate recent infection
Important for RF & glomerularnephritis diagnosis
What are the exotoxins secreted by s.pyogenes? Why do peoples symptoms to these toxins vary?
SpeA/B/C = pyrogenic exotoxins
Superantigens
Responsible for Scarlet Fever & TSS
HLA dep response - will intrinsically vary from person to person
How is staph pyogenes transmitted?
Oral secretions
Skin lesion contact
Which pus forming skin infections can s.pyogenes cause?
Impetigo
Erysipelas
Nec fasc
TSS
How do you test for s.pyogenes in strep throat?
Rapid antigen
- V. specific - if positive, you’ve got it
Also take swab culture in case false negative
Why do you treat strep throat?
Prevent Scarlet Fever!
Drugs for pharyngitis
Penicillin
Allergic:
- Macrolides
- Clindamycin
What are the presenting symptoms of scarlet fever?
Rash started on trunk
Strawberry tongue
Broken capillaries –> skin folds
Peeking skin (desquamation)
What are some tell tale symptoms of impetigo?
Honey crusted skin lesions
- Look like this b/c of pus coming out of the wounds
Drugs for impetigo
TOPICAL Bacitracin Mupirocin MRSA/more extensive disease Amoxicillin/clavulanic acid Cephalexin
What is erysipelas?
MENTAL TIE TO S.PYOGENES
Red, swollen rash w/ sharp edges
Form of cellulitis
+ “Fever and I don’t feel good”
What could result for s.pyogenes weird tie to lymphatics?
Cellulitis w/ lymphagitis
= Streaking to draining lymph node
What are the clinical symptoms for nec fasc?
Pain out of proportion
Hemorrhagic bullae
May have progressed to septic shock
Explain how s.pyogenes can cause toxic shock syndrome?
Had s.pyogenes skin infection
SpeC toxin = superantigen
+ you have the right HLA to react
Cytokine storm
Which s.pyogenes infection can progress to cause RF?
Strep throat ONLY!
What are you concerned about if you don’t clear the s.pyogenes infection causing RF?
Repeated RF –> rheumatic heart disease
Irreversible damage
How long does glomerulonephritis present after the primary s.pyogenes infection? What types of s.pyogenes infections can cause this complication?
2 weeks post pharyngitis OR skin infection
