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
