KEY CNS PATHOGENS

Virus enters via olfactory/trigeminal nerve or reactivation → Travels retrograde to CNS → Causes tissue injury via lysis and immune-mediated damage

Describe the pathogenesis of HSV-1 encephalitis.

PCR of CSF to detect viral DNA

What is the gold standard for HSV diagnosis?

Autoimmune encephalitis, especially anti-NMDAR, due to exposed CNS antigens

What is a complication of HSV-1 encephalitis after viral clearance?

Pili (attachment)
Opacity proteins (tissue specificity)
LOS (triggers immune response, mimics host)
Capsule (antiphagocytic, used for serotyping)

What are key virulence factors of N. meningitidis?

Ceftriaxone, switch to Penicillin after susceptibility confirmed

What is the empiric treatment for meningococcal meningitis?

Given to close contacts within 24 hours
Drugs: rifampin, ciprofloxacin, azithromycin, ceftriaxon

What is the role of chemoprophylaxis in meningococcal infection?

Evades phagocytes, produces melanin and mannitol
CSF has dopamine and lacks inhibitory factors → ideal growth medium

What makes C. neoformans neurotropic?

India ink stain
Cryptococcal antigen
Culture (positive in >90% of non-AIDS cases)

What is the diagnostic hallmark in CSF for Cryptococcus?

Induction: Amphotericin B + Flucytosine
Maintenance: Fluconazole

What is the standard treatment for cryptococcal meningitis?