Microbiology 1: CNS Infections And Meningitis Flashcards by .. ...

What is the most frequent route of entry for pathogens causing CNS infections ?

Haematogenous spread

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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)

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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)

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Which organism is a common cause of neonatal meningitis ?

Group B streptococcus

Floral bacteria in the mothers vagina

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What organism commonly causes chronic meningitis ?

Tuberculosis

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What organisms can cause aseptic meningitis ?

Enterovirus - coxsackievirus
Herpes simplex

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Which organisms cause acute meningitis ?

N.meningitidis
Streptococcus.pneumonia
Haemophilus.influenza

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What is aseptic meningitis?

also known as viral meningitis - no pus found
Usually acute viral meningitis
not as severe as bacterial

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Which N.meningitidis serotypes are there vaccinations for ?

B and C

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Which virus transferred by vectors including birds and mosquitoes is becoming a leading cause of encephalitis world wide ?

West Nile virus

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Name a bacterial cause of encephalitis ?

Listeria

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Which organisms can cause encephalitis via local invasion ?

Amoebae (found in warm water)

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Which organism causes encephalitis via oral route ? (Eating cat poo 🤮)

Toxoplasmosis- e.g toxoplasma gonadii

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Most common cause of viral encephalitis in UK

Herpes

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What are the most common organisms responsible for brain abscesses ?

Why are brain abscesses dangerous?

Streptococci
Staphylococci
NB these are common ENT pathogens

Dangerous since cause death due to pressure-related issues

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What is the most common route of entry for organisms causing brain abscess ?

Another route?

Local extension e.g from mastoiditis or sinusitis

Other route: haematogenously

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Name a common spinal infection ?

Pyogenic vertebral osteomyelitis

If left untreated, it can lead to permanent neurological deficits, significant spinal deformity, or DEATH

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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

**ADD TABLE FROM NOTES PLS**

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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

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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

**ADD TABLE FROM NOTES PLS**

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

Herpes meningitis vs herpes encephalitis

Herpes meningitis does NOT need therapy BUT herpes encephalitis is a MEDICAL EMERGENCY

Which imaging is best for detecting parenchymal abnormalities e.g. abscesses and infarctions?

Which is more commonly available and so used?

Best: MRI

More used: CT

Culture and microscopy shows a gram +ve, alpha haemolytic diplococcus organism, what is the likely organism causing the meningitis ?

Streptococcus. Pneumoniae

this is Gram POSITIVE a-haemolytic diplococcus
Gram positive = pneumococcus (diplococci) = Stains purple on gram stain (Positive = Purple)
Gram negative = meningococcus = Stains pink on gram stain

Culture and microscopy shows a gram -ve diplococci which is non-haemolytic, what organism is the likely cause of this meningitis ? What would agar show?

Meningococcus (Neisseria meningitides) - gram NEGATIVE cocci * stains PINK Agar would show lots of neutrophils

Culture and microscopy shows gram +ve purple rods, what organism is the likely cause of this meningitis ?

Listeria monocytogenes

A 45-year-old presents with headache and neck stiffness over a period of weeks. LP shows cuboidal structures that appear red against a blue stain. What is the causative pathogen?

TB * NB this happens over WEEKS (chronic meningitis cause) * This is Ziehl-Neelsen stain

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 ?

Amoxicillin

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 myelitis

poiovirus

common causes of neurotoxin release

clostridium tenani clostridium botulinum

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

how should CSF infections be managed

* within 30 mins - clinical assessment * after 1-2 hours - CFS analysis * 24-48 hrs - CSF cultures

How to clinically differentiate encephalitis from meningitis

The disturbance of _cognitive function_ in ecephalitis is what differentiates meningitis to encephalitis

Why might you consider doing MRI/CT before LP for CNS infection? When do you need to do this?

Check for raised ICP ONLY do this if you think there may be raised ICP on clinical suspicion - If you clinically think that the patient does NOT have raised ICP, then you do NOT need to do a CT/MRI before doing an LP (clinical = neuro exam)

4 samples to send for Ix if meningitis suspected

* CSF * Blood culture * Throat swab * Sputum culture

What colour does gram positive stain?

Stains purple on gram stain (Positive= Purple) * e.g. Gram positive = pneumococcus (diplococci)

What colour does gram negative stain?

Stains pink on gram stain e.g. meningicoccus)

Which group tend to be infected more by listeria for meningitis? (2)

* Old age (have age-related immunosenescence) * Immunosuppressed pts

Most common infection of CNS Which age group does it mainly affect? How does it resolve?

Aseptic Meningitis (viral) Mainly affects children \< 1 year Self-limiting condition (resolves over 1-2 weeks) - NO antivirals

Which group of pts are mainly affected by chronic meningitis + what is common causative organism?

* group: immunosuppressed + old * common organism: TB

\*\*PLEASE COULD YOU IMAGE OCCLUDE THE TABLE UNDER 'CLINICAL SYNDROMES' - JUST OCCLUDE EACH ROW OF SYNDROME (SO 4 BOXES IN TOTAL)\*\*