Microbiology 1: CNS Infections And Meningitis Flashcards
What is the most frequent route of entry for pathogens causing CNS infections ?
Haematogenous spread
List 4 routes of entry to the CNS for pathogens
Haematogenous spread (meningococcus, pneumococcus) Direct implantation (after surgery) Local extension (from the ear) PNS into CNS (rabies)
Which organism is a common cause of neonatal meningitis?
Group B streptococcus
Floral bacteria in the mothers vagina
What organism commonly causes chronic meningitis ?
Tuberculosis
What organisms can cause aseptic meningitis ?
Enterovirus - coxsackievirus
Herpes simplex
Which organisms cause acute meningitis ?
N.meningitidis
Streptococcus.pneumonia
Haemophilus.influenza
Which N.meningitidis serotypes are there vaccinations for ?
B and C
Which virus transferred by vectors including birds and mosquitoes is becoming a leading cause of encephalitis world wide ?
West Nile virus
Name a bacterial cause of encephalitis ?
Listeria
Which organisms can cause encephalitis via local invasion ?
Amoebae
Which organism causes encephalitis via oral route ? (Eating cat poo 🤮)
Toxoplasmosis- e.g toxoplasma gonadii
What are the most common organisms responsible for brain abscesses ?
Streptococci
Staphylococci
What is the most common route of entry for organisms causing brain abscess ?
Local extension e.g from mastoiditis
Name a common spinal infection ?
Pyogenic vertebral osteomyelitis
What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?
CSF appearance: clear Cells: 0-5 leukocytes Gram stain/antigen tests: negative results Protein: 0.15-0.4 g/l Glucose: 2.2-3.3mmol/m
Normal
No organisms
What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?
CSF appearance: Turbid Cells: 100-2000 polymorphs Gram stain/antigen tests: positive results Protein: 0.5-3.0 g/l Glucose: 0-2.2 mmol/l
Purulent meningitis (bacterial)
Meningococcus
Pneumococcus
Listeria
What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?
CSF appearance: clear/slightly turbid Cells: 15-500 lymphocytes Gram stain/antigen tests: negative results Protein: 0.5-1 g/l Glucose: 2.2-3.3 (normal)
Aseptic meningitis
Coxsackie virus
Echovirus
TB
Could also be:
bacterial meningitis partially treated with ABx
Encephalitis
Brain abscess
What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?
CSF appearance: clear/slightly turbid
Cells: 30-500 lymphocytes/ some polymorphs
Gram stain/antigen tests: negative results (scanty acid fast bacilli)
Protein: 1.0-6.0 g/l (high)
Glucose: 0-2.2 (normal)
Tuberculous meningitis
Mycobacterium TB
Culture and microscopy shows a gram +ve, alpha haemolytic diplococcus organism, what is the likely organism causing the meningitis ?
Streptococcus. Pneumoniae
Culture and microscopy shows a gram -ve diplococci which is non-haemolytic, what organism is the likely cause of this meningitis ?
Meningococcus (Neisseria meningitides)
Culture and microscopy shows gram +ve rods, what organism is the likely cause of this meningitis ?
Listeria monocytogenes
Culture and microscopy shows a positive Ziehl-Nielsen stain what organism is the likely cause of this meningitis ?
TB
India ink stain: shows orbit structures (yeast cells with surrounding halos)
Lumber puncture: high opening pressure
IN a patient with HIV
What is the likely causative organism of this meningitis ?
Cryptococcus Neoformans
Which organism commonly causes meningitis in men who have sex with men (MSM)
Cryptococcus Neoformans
Which drug is effective against Meningococcus, pneumococcus, haemophilus and e.coli ?
Ceftriaxone I.V
Which drug is effective at treating Listeria ?
Ampicillin
Which organism is most commonly associated with recurrent aseptic meningitis (Mollaret’s meningitis) ?
HSV-1 and HSV-2
Which organisms are the most common cause of aseptic meningitis ?
Enterovirus (80%) - Echovirus, coxsackie virus
common causes of encephalitis
rabies virus
arboviruses
prions
amoeba
common causes of myelitis
poiovirus
common causes of neurotoxin release
clostridium tenani
clostridium botulinum
what is meningitis
inflammatory process of the meninges and CSF
neurological damage caused by:
- direct bacterial toxicity
- indirect inflammatory processes and cytokine release
- shock, seizures and cerebral hypoperfusion
can be classified into acute, chronic, aseptic (viral)
list other causes of meningitis
listeria monocytogenes
group B strep
E. coli
rare:
TB, S. Aureus, T. Pallidum, cryptococcus neoformans
describe the processes whereby septicaemia occurs
capillary leak - albumin and other plasma proteins lead to hypovolaemia
coagulopathy - leads to bleeding and thrombosis
metabolic derrangeent - acidosis
myocardial failure and multi-organ failure
complications of TB meningitis
common in immunosuppressed
complications = tuberculosis granulomas
tuberculosis abscesses
cerebritis
there is leptomeningeal enhancement
features of aseptic meningitis
most common infection of the CNS coxsackie group B echoviruses usually in children <1 year self-limiting, resolves in 1-2 weeks
what is toxoplasmosis
obligate IC protozoal parasite
spread via oral, transplacental or organ transplant route
causes severe infection in immunocompromised
affects organs including grey and white matter of brain, retinas, alveolar lining of lungs, heart, skeletal muscle
which mode of screening is best to detect parenchymal abnormalities
MRI better than CT to look at functional tissue
how should CSF infections be managed
within 30 mins - clinical assessment
after 1-2 hours - CFS analysis
24-48 hrs - CSF cultures
