Infections of the CNS Flashcards
What are the clinical features of menigitis?
- Headache, sore throat, drowsiness
- Rapid onset fever, photophobia, neck stiffness
- Level of consciousness progressively falls
- Petechial or purpuric rash
- Intravascular coagulation, endotoxaemia, shock, multi-organ failure, raised intracranial pressure.
What are the other symptoms of meningitis that occur in babies?
– Tense or bulging soft spot on their head
– Refusing to feed
– Irritable when picked up, with a high pitched or moaning cry
– A stiff body with jerky movements, or else floppy and lifeless
Define meningitis
Inflammation of the meninges
Define encephalitis
inflammation of the brain
Define sepsis
whole body inflammation
What is the blood brain barrier and how do microbes invade it?
- Blood-brain barrier (BBB)
- Created by tightly packed endothelial cells lining the blood vessels in the brain.
- Endothelial cells mechanically supported by thin basement membrane.
What does a breach of the BBB caus?
Breach by infectious agents causes encephalitis.
Describe the Blood-CSF barrier
– Similar barrier at arachnoid membrane and in ventricles.
What does a breach of the blood-CSF barrier cause?
– Breach by infectious agents causes meningitis.
What are the mechanisms of direct spread that result in microbes entering the CNS?
- Sinuses
- Otitis media
- Skull fracture
What blood tests should be taken to confirm a diagnosis of meningitis?
- Blood
- Culture
- NAAT
- Glucose
- FBC
- UandE
- Clotting
What CSF tests should be taken to confirm a diagnosis of meningitis?
- CSF
- WCC
- gram stain
- NAAT
- India Ink
- Ziehl-Neelsen stain
What are the main bacterial causes of menigits?
- Neisseria meningitidis
- Haemophilus influenzae
- Streptococcus pneumoniae
- Mycobacterium tuberculosis
What are the main viral causes of meningitis?
- Enteroviruses:
- Echovirus
- Coxsackie viruses A & B
- poliovirus
- Herpes viruses:
- Herpes simplex 1 & 2
- Paramyxovirus:
- Complication of mumps
What are the fungal causes of meningitis?
Cryptococcus neoformans
What are the protozoa causes of meningitis?
- Amoebae
- Naegleria
- Acanthamoeba
What are the main methods used by pathogens to breach the barriers in the body?
– Growing across & infecting cells comprising barrier
– Passive transfer in intracellular vacuoles
– Carriage across in infected white blood cells
Describe the features of meningitis caused by N. Menungitidis
- Meningococcal disease
- Gram negative
- Intracellular diplococus
- Only infects humans
- Exists as normal microbiota in nasopharynx
- Distinct pathogenic serogroups
- Transmission by droplet spread or direct contact from carriers 5 strains – A, B, C, W135, Y
Describe the main features of H. Influenzae meningitis
- Gram-negative
- Coccobacilli
- Six capsular serotypes (a-f) known to cause disease
- Most virulent strain is H. influenzae type b (Hib)
What are the main virulence factors of bacteria that cause meningitis?
- Anti-phagocytic polysaccharide capsule
- Endotoxin
- IgA protease
- Outer membrane proteins (OMPs)
- Pili (fimbriae)
What are the main features of Strep. pneumoniae meningitis?
- Pneumococcal disease
- Chains of cocci
- Gram positive
- Exists as normal microbiota in nasopharynx
- Also causes pneumonia, otitis media
What are the main causes of meningitis in neonates?
- Escherichia coli
- Group B Streptococcus
- Listeria monocytogenes
What are the main causes of meningitis in children under 5?
Neisseria meningitidis
Haemophilus influenzae
What are the main causes of meningitis in young adults?
Neisseria meningitidis
What are the main causes of meningitis in older people?
Streptococcus pneumoniae
Listeria monocytogenes
What are the main causes of meningitis in those who are immunosuppressed?
Mycobacterium tuberculosis
Cryptococcus neoformans
What are the main complications of bacterial meningitis?
- sepsis
- intellectual deficit
- deafness
- arthritis
- skin necrosis
What are the main vaccines assoicated with bacterial meningitis?
- MenC (meningococcal group C)
- Hib (Haemophilus influenzae type B)
- BCG (Mycobacterium tuberculosis)
- Strep. Pneumoniae (pneumonococcal)
- MenB (meningococcal group B)
- Men ACWY (quadrivalent)
What is a notifable disease? And why are they important?
- Any disease that is required by law to be reported to government authorities
- Allows the authorities to monitor the disease
- Provides early warning of possible outbreaks
What are the main features of viral meningitis?
- Milder disease than bacterial but more common
- NAAT is a valuable diagnostic tool
- Identify in faeces, urine, CSF, serology
- No specific treatment
- Aciclovir (herpes)
- Use of vaccination (polio)
What are the main features of tuberculosis meningitis?
- Frequently associated with miliary TB
- Usually develops when Rich focus discharges contents in sub-arachnoid space
- Acid-fast bacilli in CSF smear
- NAAT and culture from CSF
- Treated with rifampicin, isonazid, pyrazinamide, ethambutol
- Vaccination with BCG
What are the main features of encephalitis?
- Usually viral in origin
- Viruses gain access to CNS via blood or neurons
- Primary encephalitis – First exposure to virus results in virus directly affecting brain / spinal cord
- Secondary encephalitis – Virus first infects another part of body, then affects CNS when reactivated
What are the main causes of encephalitis?
- Cerebral malaria (Plasmodium sp.)
- Toxoplasma gondii
- Rabies
- Herpes simplex virus
- Prions
- Mumps virus
- Polio virus
- Candida albicans
- Arboviruses
- Lyme disease (Borrelia burgdorferi)
- Japanese encephalitis virus
- West Nile virus
What are the main signs of cerebral dysfunction?
- abnormal behaviour
- seizures
- altered consciousness
- nausea
- vomiting
- fever
What are the main features of a brain abscess?
- Begin as diffuse inflammation of brain matter progressing to focal lesion
- Arise from pia mater suppuration
- Visualised by MRI or CT scans
- Diagnosed by culture from aspirated pus
What are the main causes of brain abscess?
- Predisposing factors
- Otitis media
- Mastoiditis
- Sinusitis
- Oral-nasopharyngeal microbiota
- Aerobic (S. aureus, Strep. milleri)
- Anaerobic (Bacteroides sp., Fusobacterium sp.)
- Immunocompromised (eg. HIV, transplantation)
- Protozoa (Toxoplasma gondii)
- Fungi (Candida sp., Nocardia sp., Aspergillus sp.)
