What are key clinical features and the first investigations OF meningitis ?
A:
• Headache, neck stiffness, photophobia, fever.
• When suspecting meningitis → Order CSF + blood cultures immediately (STAT).
What is lumbar puncture (LP) protocol?
A:
• Performed under sterile technique.
• Three tubes:
1. Chemistry
2. Microbiology
3. Hematology
• Send immediately (NO delay, NO refrigeration).
• Lab processing must be STAT
What are the major case of meningitis?
- Major bacterial causes: Haemophilus, meningococcus & pneumococcus
What are major neonatal causes of meningitis?
- Neonates: GBS, E. coli, L.monocytogenes, Klebsiella, Salmonella
What are VP shunt infection causes of meningitis?
- VP shunt: CONS (S. epidermidis), Acinetobacter, Pseudomonas, S.aureus
Which pathogens cause meningitis in immunosuppressed (↓ IS) patients?
A:
• Listeria in adults
• Cryptococcus neoformans in all age groups
What are the key features of aseptic meningitis?
A:
• CSF: Negative culture + high cell count
• Severity: Less serious than bacterial meningitis
• Duration: Short duration → most likely viral
• Exception: Child sick > 1 week → suspect MTB
What are the major causes of lymphocytic CSF?
A:
• Enteroviruses → most common cause
• HSV → high-mortality encephalitis
• TB, Cryptococcus, Leptospirosis
• Syphilis → “the great imitator”
• Non-infectious causes: autoimmune diseases, malignancies, drugs
What are the key characteristics of Haemophilus influenzae?
• Gram-negative small coccobacilli, show pleomorphism
• Grow best in 5–10% CO₂–enriched media with seminal odor
• Strains may be encapsulated or non-encapsulated
• Type b capsule = polymer of ribosyl ribitol phosphate (major virulence factor)
• Capsule antigen detection (especially pretreated patients): slide latex agglutination test
What two factors does H. influenzae need for growth?
A:
• X-factor (hemin): heat-stable, needed for cytochrome C & enzymes
• V-factor (NAD): heat-labile, needed for oxidation–reduction processes
Why doesn’t H. influenzae grow on blood agar, and why does it grow better on chocolate agar?
A:
• Blood agar: No growth because V-factor (NAD) is destroyed by heating + NADase → V-factor unavailable.
• Chocolate agar: Good growth because lysed RBCs release both X-factor & V-factor.
What is satellitism in H. influenzae?
A:
Enhanced growth near an S. aureus colony on blood agar because S. aureus provides V-factor.
Why is H. influenzae meningitis rare before 2 months, when is it most common, and what is its major neurological complication?
▪ Rare in 1st 2 months of life: due to maternal transplacental IgG
▪ Common at 6 to 24 months of age
▪ Neurological sequelae mainly hearing loss 10-30%,
What non-invasive diseases are caused by non-encapsulated H. influenzae strains?
A:
• Sinusitis
• Otitis media
• Conjunctivitis
• Acute COPD exacerbation
What are the key identifying features of Neisseria species?
A:
• Gram-negative oval “bean/kidney-shaped” diplococci
• Oxidase positive
• Intracellular inside PMNs
What invasive disease does Neisseria meningitidis most commonly cause, and what are its key features?
A:
• Purulent meningitis (accounts for 2/3 of invasive cases)
• Second most common cause of meningitis
What is Waterhouse–Friderichsen syndrome caused by N. meningitidis, and what are its main clinical features?
1/3 of N.meningitis
A:
• Occurs in children <10 years
• Fulminant septicemia without meningitis
• Massive adrenal hemorrhage → adrenal failure
• Petechiae/purpura, hypotension, septic shock, DIC
• Rapid progression → organ failure, coma, death
What are the key laboratory characteristics of Streptococcus pneumoniae?
A:
• Optochin: Sensitive
• Bile solubility: Soluble
• Quellung reaction: Positive (capsule swelling)
• Omni-serum test: Positive
• Colony type: Draughtsman colony (depressed center)
• Gram stain: Gram-positive diplococci
What is the most common cause of bacterial meningitis?
A:
Streptococcus pneumoniae.
What are the capsule features of Streptococcus pneumoniae?
A:
• Polysaccharide, anti-phagocytic
• Has 90 serotypes
• Forms mucoid colonies
What does pneumolysin do?
A:
• Membrane-damaging toxin
• Inhibits: neutrophil chemotaxis, phagocytosis, respiratory burst
• Suppresses lymphocyte proliferation and Ig synthesis
What are the effects of autolysin in pneumococcus?
A:
• Breaks peptidoglycan cross-linking → bacterial lysis
• Produces Draughtsman colony
• Causes massive inflammatory response
What are the major diseases caused by S. pneumoniae?
A:
• Pneumonia (most common cause in adults)
• Otitis media & sinusitis (most common in children)
• Meningitis (most common cause overall)
What are key features of pneumococcal meningitis?
A:
• Hematogenous spread from pharynx
• Bimodal incidence: <3 years & >45 years
• Causes recurrent meningitis in skull base fracture
