1b Meningitis and Group A Streptococcal Flashcards Preview

Term 5 - PathoPhysio > 1b Meningitis and Group A Streptococcal > Flashcards

Flashcards in 1b Meningitis and Group A Streptococcal Deck (13):
1

  • Bacterial Meningitis
    • Differential diagnosis (5)

  1. Viral meningitis
    • More gradual onset
    • CSF lower protein, higher glucose, fewer cells, more lymphocytes
    • PCR techniques can identify in hours to a day on CSF specimens (enteroviruses, HSV‐2 and HSV‐1)
  2. Fungal meningitis
    • Cryptococcus neoformans most common. Look for immunosuppression. Gradual not acute onset
  3. TB meningitis
    • Especially in young children, reactivation disease in adults
  4. Encephalitis
    • Consider viral origins
    • Seasonality to West Nile virus
    • Chikungunya associated with small rate of encephalitis
    • HSV‐1 high mortality, morbidity. Treatable with IV acyclovir
  5. Subarachnoid Bleed
    • Thunderclap headache, stiff neck, decreased level of consciousness
    • No fever
    • Also medical emergency. Needs CT, LP

2

Bacterial Meningitis - Main long term sequelae

  • Prognosis: Morbidity
    • Main long term sequelae include hearing loss, paralysis or weakness, impaired cognition or speech and cranial nerve palsy
    • Predictors of poor outcome include coma, seizures and hypotension
    • Incidence of long term sequelae in children may be as high as 50%

3

  • Mechanism of resistance to penicillin 
    • Pneumococcus 
    • H. influenzae
    • MRSA

  • Pneumococcus - change in penicillin binding protein (PBP) affinity
  • H. influenzae - beta lactamase
  • MRSA - substituted PBP

4

Bacterial Meningitis - Treatment

A penicillin, third generation cephalosporin and/or vancomycin all given intravenously in high dose

5

Streptococcal pharyngitis - sequelae

  1. Poststreptococcal glomerulonephritis (PSGN),
  2. Rheumatic fever
  3. Toxic shock syndrome
  4. Local and distant site suppurative infection
  5. GAS pharyngitis may be accompanied by a rash and the findings referred to as scarlet fever

6

  • Pathogenic mechanism GAS
    •  Main virulence factors include (9):

  1. Capsule in some strains (decreased phagocytosis)
  2. Lipoteichoic acid in peptidoglycan cell wall (adhesion)
  3. M‐protein (inhibits antibody binding and compliment related opsinization)
  4. Fibronectin binding protein (adhesion)
  5. Vimectin (muscle adhesion)
  6. Streptolysin O (hemolysis on blood agar. Titers high and help with diagnosis of PSGN and rheumatic fever)
  7. Hyaluronidase (skin, deep tissue spread)
  8. Streptokinase (binds plasminogen → plasmin → fibrin → fibrin degradation products)
  9. Streptococcal pyrogenic exotoxins (SPE) A,B and C toxins. (fever, rash of scarlet fever, streptococcal toxic shock syndrome toxin. May also function as superantigens and induce cytokine production.)

7

Poststreptococcal glomerulonephritis (PSGN)

  • Risk greatest children 5 to 12 and adults > 60
  • Can occur following pharyngitis or skin infection
  • Related to circulating strain virulence factors (SPEB)
  • Edema, hematuria, hypertension

8

Scarlet fever

  • Diffuse rash in association with pharyngitis
  • Starts in head and neck. Circumoral pallor and strawberry tongue also found. Rash is raised and has sandpaper like appearance
  • Rash spreads to torso and then limbs
  • Eventually desquamates (peels like a sunburn)

9

Acute Rheumatic Fever

  1. Occurs after streptococcal pharyngitis (2 to 3 weeks later)
  2. Arthritis, carditis, subcutaneous nodules, chorea (movement disorder), erythema marginatum (rash)
  3. May have fever, increased ESR and CRP
  4. Usually children age 5 to 15.
  5. More common in developing world
  6. Late sequelae include rheumatic heart disease with mitral stenosis and increased risk for endocarditis

10

Peritonsilar abscess

  • Can extend into deep spaces of neck
  • Other organisms can become involved (Fusobacterium necrophorum) Anaerobe resistant to azithromycin. (azithromycin is used for sore throat in penicillin allergic patients) Leads to septic thrombosis of jugular vein and septic pulmonary emboli to lungs causing lung abscess
  • Require surgical drainage of neck abscess

11

Otitis media

  • Extension to middle ear via Eustachian tube
  • Less than 10% of causes of otitis media 
  • Otalgia, fever, irritability

12

  • Complications of GAS
    • Local suppurative extension - Necrotising fasciitis

  • Bacteremic spread to site of blunt trauma. Infection spreads along fascial planes killing tissue above fascia. Skin becomes necrotic with large bullae (blisters).
  • May also be complication of chickenpox (varicella zoster virus infection with vesicular (small fluid blisters) skin rash
  • High mortality rate. Requires urgent surgical debridement
  • Bacteremia more common from skin site than pharynx

13

  • Streptococcal pharyngitis:
    • Principles of Treatment

  • Duration of treatment
    • Treat long enough to decrease risk of rheumatic heart disease
    • 10 days of penicillin
    • 5 days therapy sufficient with agents with longer half life (azithromycin, cefpodoxime and cefdinir)
  • Resistance to penicillins has not been reported.
  • Macrolide or clindamycin resistance exists
  • Group C and G strep do not have the same sequelae and therapy decisions are based on clinical severity