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MS2 Unit 3 > Micro: Bacterial Infections of CNS > Flashcards

Micro: Bacterial Infections of CNS Flashcards

1
Q

Describe Neisseria meningitidis bacteriology

A
  • Gram (-) diplococci, facultative intracellular
  • Human restricted
  • Encapsulated
  • ~13 serotypes
  • Oxidase +, catalase +
  • Ferments glucose and maltose, NOT sucrose or lactose
  • Grows on chocolate agar or Thayer Martin, NOT blood agar
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2
Q

Pathogenesis of Neisseria meningitidis

A
  • Airborne droplets
  • Colonizes nasopharynx
  • Spread + colonization can be enhanced by concomitant URI
  • Often resolves w/o symptoms, IgG-enhanced complement and neutrophils defend, leaving lifelong immunity to infecting strain
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3
Q

What are the 3 ways N. meningitidis can affect you?

A
  1. Enters bloodstream –> meningococcemia
  2. Colonizes joints –> septic arthritis
  3. Colonizes meninges –> meningitis, fatal if untreated
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4
Q

Virulence factors of Meningococci

A
  1. IgA protease - cleaves IgA, reduces defense of mucus membrane
  2. Polysaccharide capsule - resists phagocytosis
  3. Endotoxin LOS - causes fever, shock
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5
Q

Exam findings for N. meningitidis septic arthritis and meningitis

A

1/3 cases adult, 2/3 peds
Septic arthritis: joint pain –> draw joint fluid

Meningitis: Adults - fever, headache, stiff neck, coma
Kids: irritability, convulsions, lassitude, fever, abd discomfort/vomiting
Both: CSF tap + admit

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6
Q

Exam findings for N. meningitidis meningococcemia

A

Fever, hourly-spreading petechial skin rash –> draw blood + CSF, admit to ICU
- 5-15% develop Waterhouse Friderichen syndrome (fatal)

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7
Q

Waterhouse-Friderichen syndrome

A
  • A fatal complication of meningococcemia

- High fever, shock, widespread purpura, DIC, thrombocytopenia, destruction of adrenal glands

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8
Q

Labs for septic arthritis, meningitis, and meningococcemia

A

Septic arthritis: gram stain and culture joint fluid on chocolate agar

Meningitis: CSF- increased PMNs, Gram stain and culture on chocolate agar. Gram (-) cocci in CSF sufficient for diagnosis. Alt latex agglutination test for capsule polysaccharide in CSF

Meningococcemia: blood - gram stain and culture on chocolate agar, test for DIC

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9
Q

How can you differentiate N. meningitidis from N. gonorrheae?

A

Only meningococci ferment maltose

- alt, IF

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10
Q

N. Meningitidis treatment

A

Penicillin G
Alt. Ceftriaxone, cefotaxime, cefuroxime, chloramphenicol
- Prescribing glucocorticosteroids for rash and arthritis is VERY BAD

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11
Q

Prevention of N. meningitidis

A
  • close contacts of patient zero get prophylactic rifampin, ceftriaxone, or ciprofloxacin
  • vaccines recommended: travelers, college, 11-12 y/os
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12
Q

Group B strep bacteriology

A

S. agalactiae

  • encapsulated Gram + cocci
  • B-hemolytic
  • polysaccharide toxin virulence factor
  • pilus-like attachment virulence factor
  • serotype-specific Ab-mediated immunity
  • Normal vag flora, transmits to bb before and during delivery
  • Can also be normal flora in GI, upper respiratory tract
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13
Q

Besides neonates, what is another risk group for GBS?

A

Geriatrics w/ predispositions (diabetes, malignancy, CHF)

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14
Q

GBS exam

A

Patient presents with pain, fever, symptoms specific to site

Meningitis: spinal tap for Gram + cocci in pairs or small chains

Cellulitis/abscess: Gram stain, culture appropriate fluid. CT/MRI for deep abscess

ECG for endocarditis

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15
Q

GBS labs

A

CAMP test: CAMP factor secreted by GBS, enhances activity of B-hemolysin from S. aureus

Hippurase/Hippurate test: colorimetric test for hippurase, produced by GBS (and others)

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16
Q

GBS treatment

A

IV penicillin or amoxicillin

  • vanc if allergic
  • surgical intervention if necessary
17
Q

Pneuomococcus Bacteriology

A

Strep pneumoniae

  • Gram +, catalase (-), alpha hemolytic, facultative anaerobe
  • Form diploccoci in chains on culture
  • Pathogenic strains are encapsulated
  • MCC of community acquired pneumonia, bacterial meningitis, bacteremia, otitis media. Causes lots of other shit too, kills many children worldwide
18
Q

Pneumococcus Pathogenesis

A
  • colonizes upper resp tract w/ adhesion virulence factors
  • infections peak in Fall and Winter
  • contained by innate immunity in healthy people, in kids or people with lung issues or immunosupression, bacteria spreads
  • CAPSULE is major virulence factor, but also has: IgA protease, teichoic acid
19
Q

What are the 2 types of pneumococcal disease?

A
  1. direct extension: sinuses, bronchi, eustachian tubes
  2. hematogenous spread: blood, joint fluid, peritoneum, CSF
    - capsule protective against phagocytosis UNLESS anti-capsule IgG is present
    - pathogenic strains all contain pneumolysin, some have hemolysin, neuraminidase, hyaluronidase
    - infection raises STRONG INFLAMMATORY RESPONSE
20
Q

Pneumococcus exam for diseases of direct extension

A
  • sinusitis, otitis media, bronchitis, pneumonia
    -pneumonia kills 10-20%
  • patient looks ill and anxious
  • predispositions: asthma, COPD, chronic bronchitis, smoking/secondhand smoke
    Radiology: adolescents and adults -> lobar consolidation
    infants + little kids -> scattered consolidation, bronchopneumonia
21
Q

Pneumococcus exam for hematogenous spread

A

-meningitis, septic arthritis, pericarditis, endocarditis, osteomyelitis
- bimodal distribution (under 5, older than 65) + immunosuppressed
Meningitis: mental status changes, lethargy, delirium, Brudzinski +, cranial nerve palsies, focal neuro defects

22
Q

Labs for non-invasive, invasive pneumococcus

A

Non-invasive: can be treated based on exam, optional gram stain

Invasive: Gram stain and culture

  • antibiotics sensitivity testing
  • urine antigen testing useful in pneumonia in young kids who don’t produce enough sputum
23
Q

Typical spinal tap findings in BACTERIAL MENINGITIS

A
  • elevated opening pressure
  • elevated WBC and neutrophils
  • elevated protein
  • decreased glucose
  • highly elevated lactic acid
  • Gram stain and culture + unless abx started >4 hrs prior to tap
24
Q

Pneumococcus treatment (noninvasive)

A

Severe pneumonia: admit, vancomycin

If less than severe pneumonia: amocixillin or cephalosporin, fluoroquinolones or doxy for adults only. outpatient.

25
Q

Pneumococcus treatment (invasive)

A

Admit, start abx, start cultures, do abx susceptibility tests on cultures

  • initial abx are vancomycin + ceftriaxone or cefotaxime
  • if tests come back resistant, add rifampin, meropenem, or chloramphenicol
  • steroids can be used w/ caution in addition to abx, early in abx course
  • cellulitis, septic arthritis -> surgery
26
Q

Pneumococcus prevention

A
  • Prevnar7 vaccine –> raises protective IgG against capsules of 7 serotypes most commonly caused invasive disease prior to 2000
  • Prevnar13: added 6 newly problematic serotypes

MS2 Unit 3 (21 decks)

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