CNS infections Flashcards
Bacterial meningitis
- Neonates up to 2 mo: Strep, agalactiae, E. coli, Listeria monocytogenes
- Infancy & child: Strep. Pneumonia, N. meningitides, H. influenza
- Ado: N. meningitides, Strep. Pneumonia
- 20-60 YO: Strep. Pneumonia, N. meningitides, Listeria monocytogenes, Gram –ve
CNS pathogens and assoc med conditions
- S. pneumoniae: Alcoholism, skull fractures, myeloma, splenectomy
- H. influenzae: Alcoholism, post splenectomy, hypogammaglobulinemia
- N. meningitides: Post splenectomy, complement deficiency
- L. monocytogenes: CM1 (centrocyte/-blast marker 1) defects (Hodgkin’s disease, steroid therapy), elderly
- C. neoformans:AIDS, other CM1 defects
- S. aureus: CSF shunts
- Herpes B encephalitis: Monkey handlers or monkey bite
- Meningococcal meningitis: Overcrowding
Meningitis & Encephalitis: CSF analysis
Opening Pressure
– Lateral decubitus position
– Normal pressure: 70-180 mm H2O
General Appearance of CSF
– Normal: clear, colorless
– Abnormal: cloudy/turbid (↑ WBC, ↑RBC, bacteria, protein)
Detailed Apperance of CSF
- Yellow -> Blood breakdown products; Hyperbilirubinemia; CSF protein ≥150mg/dL (1.5g/L), >100,000 RBC/mm3
- Orange -> Blood breakdown products; Xanthochromia
- Pink -> Blood breakdown products
- Green -> Hyperbilirubinemia, Purulent CSF
- Brown -> Meningeal melanomatosis (Metastatic Melanoma)
Normal CSF values
- WBC count: children & adults 0-5/mm3
- 70% lymphocytes, 30% monocytes
- neonates 32/mm3
- RBC count:None
Streptococcal meningitis: Pathogenesis
- *Pathogenesis:**
- enzymes to cleave cell surface receptors
- IgA proteases on membranes
- Hyaluronate lyase: tears up BM
- Pneumolysin: hole making
Sx
- Rapid 1-2 days (or gradual)
- Impaired consciousness common
Neisseria meningitidis
Neisseria meningitidis
- RTI; Most commonly: children & young adults
- Serotype B, C & Y endemic (US) bc Type B capsule not included in vaccine
- Non-motile, Gram -ve diplococci
- Oxidase+
- encapsulated
- Kidney-bean shaped
- Fastidious
- 5-10% CO2, (Chocolate agar, Modified Martin-Thayer agar)
- Modified Martin-Thayer w antibiotics to select for N.meningitidis
- uses Maltose & Glucose
- Virulence:
- Capsule (serogroups A, B, C, X, Y & W-135)
- IgA protease: allows growth on mucosal surface
- Pili
- LOS (lipooligosacharide)
- Fimbri w antigenic variation
Sx
- Quick onset
- Acute photophobia
- Skin petechiae → ecchymoses/diffuse petechial rash -> DIC
C&C
- hypovolemia
- shock
- Waterhouse-Friedrichson
Dx
- Tumbler test: press tumbler on rash and N. meningitidis rash will not go away -> know these images
- easily spread in college dorms
- Pt w SCA and asplenic susceptible
Rx:
- Ceftriaxone
- Rifampin
Prevention: quadrivalent vaccine
Haemophilus influenzae: meningitis
- 7% cases
- Human carriage: 80% children, 20-50% adults (URT) – Many are encapsulated but not all serotypes
Etiopath
- Non-motile, Gram –ve rods
- Fastidious
- NADP (V) & Haematin (X), (Chocolate agar) – Virulence:
- Capsule (polyribitol phosphate)
- Pili
- LPS
Sx
- Slower onset (meningococcal meningitis), 3-4d
- Follows: nasopharyngitis, sinusitis or otitis media
- 1/3 survivors – neurologic sequelae
**Prevention: **Hiberix vaccine
Listeria monocytogenes: meningitis
- 8% cases (US)
- – Infants - <1 mnth (10%)
- – Adults >60y, alcoholics, cancer patients, renal transplant.
- Mortality rate:15-29%
- Serotypes: 1/2b & 4b (80% cases)
- Food-borne
Etiopath
- Gram +ve rod
- Virulence:
- Internalin A & B
- Listeriolysin O
- tears up membrane
- allows to get out of phagocytes and into cell.
Clinical features:
- – Subclinical-gastrointestinal like
- – Neonatal
- – Immunocompromised
Aerobic Gram-negative bacilli : meningitis
- Klebsiella, E. coli, S. marcescens, P. aeruginosa
- Head trauma/neurosurgery
- Neonates: E. coli K1, common
- – 50% Pregnant woman: rectum
Staphylococci: meningitis
- Uncommon: Early postneurosurgical/post-trauma
- Underlying conditions
- – Diabetes mellitus
- – Alcoholism
- – Chronic renal failure (hemodialysis)
- Hospital Acquired CNS infection: MRSA
- CSF shunts: S. epidermidis
Treponema pallidum: meninigitis
Spirocheteal meningitis
– Similar presentation to aseptic meningitis (viral)
Pathogenesis:
- can pass thru tight junctions
Clinical neurosyphilis
- – Syphilitic meningitis (0.3-2.4% untreated cases)
- – Meningovascular syphilis
- – Parenchymatous neurosyphilis
- – Gummatous neurosyphilis (rare)
Borrelia burgdorferi: meningits
- In 10-15% of untreated Lyme disease
- 2-10 wks post erythema migrans
Viral meningitis
- Most common (US): Enteroviruses
- Others
- – Mumps, Herpesvirus (including EBV, HSV, VZV), measles, & influenza
- – Arboviruses
- – Rare cases LCMV (lymphocytic choriomeningitis virus)
Etiopath
- mucosal surface colonisation RTI/GIT -> viremia -> CNS invasion -> virus spread within CNS
- Ex. human poliovirus receptor (hPVR) binding and transported retrograde on MT
- Ex2. (Non-polio) Enteroviruses: picornavidiridae, echoviruses, coxsackieviruses, enterviruses
- 85-95% all cases
- Age:Infants & Young children (no previous exposure & immunity)
- Adults (common)
- Geographic consideration - Worldwide distribution
- Seasonal consideration:
- – Temperate climate: summer/fall (water)
- – Tropical: year round (faecal-oral)
Sx
- – Usually acute benign, self-limiting, monophasic
- – Symptoms: cranial neuropathy
- – raised intracranial pressure uncommon
Mumps viral meninigitis
- Non-immunized population (meningoencephalitis) – 10-30% mumps patients
- If No parotitis (40-50% mumps meningitis)
- Benign & self-limiting
Herpes viral meningitis
- HSV have been linked to recurrent Mollaret’s meningitis *USMLE*
- characterized by sudden attacks of meninigitis sx that usually last for 2 to 7 days
- Herpes simplex 1 & 2 (0.5-3% cases)
- Post neonatal: Important to differentiate encephalitis from meningitis
- Most common: HSV 2
- 1o genital infection
- 36% women, 13% men
Other viruses causing meningitis
- Arboviruses (Arthropod-borne): Mainly encephalitis
- Lymphocytic choriomeningitis virus (Rare)
- Contact with rodents & excreta (hamsters, rats, mice)
- Lab workers, pet owners, unhygienic housing conditions
- HIV
- 1o infection/already infected or silent -> can also cause meningitis during early phase of infection
Chronic meningitis
- usually in immunocompromized host
- Must be distinguished from recurrent aseptic meningitis or encephalitis
- Symptoms: wax & wane (careful history)
- Fungal causes: Cryptococcus & Histoplasma
- Tubercular (M. tuberculosis)
Cryptocococcus neoformas (gattii): fungal meningitis
- Most common fungal cause – Via inhalation
- Immunosupressed & previously infected healthy – Mainly encephalitis
- Diagnosis: india ink (capsule)
- narrow-based budding
- encapsulated yeast
Histoplasma capsulatum: fungal meningitis
- Geographic location: Ohio & Mississippi river valley, Central America
- Able to infect immunocompetent hosts as well
- Immunosuppressed
- – AIDS
- – Solid organ transplants
- Pulmonary symptoms(minimal/absent)
- Diagnosis
- – Histoplasma antigen (CSF)
- – Cultures -ve
Coccidioides spp: fungal meningitis
- Geographic location: Central & Southern Arizona + Central Valley of California
- CA-pneumonia, Immunosuppressed individuals (AIDS)
- Mold in nature
- Yeast in tissue
- Spherule with endospores
- Diagnosis
- – Eosinophils (CSF) Wright-Giemsa Stain
- – Complement fixation test
*
Blastomyces spp: fungal meningitis
Blastomyces Dermatitidis
- Mold in nature
- Organic debris, rotting wood
- Characteristic morphology: Broad-based budding
Etiopath
- Inhalation
- Disseminates to skin
- Yeast form in tissue-
Candida: fungal meningitis (rare)
- – Neonatal ICU (use of IV catheters)
- – Postneurosurgery
- – Immunosuppressed
- oral cavity, ears (infants), vagina, catheters
- yeast form @ body temp
- fungus @ RT