Microbiology 1: CNS Infections And Meningitis

Question 1

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

Answer 1

Haematogenous spread

Question 2

List 4 routes of entry to the CNS for pathogens

Answer 2

Haematogenous spread (meningococcus, pneumococcus)  
Direct implantation (after surgery)
Local extension (from the ear)
PNS into CNS (rabies)

Question 3

Which organism is a common cause of neonatal meningitis?

Answer 3

Group B streptococcus

Floral bacteria in the mothers vagina

Question 4

What organism commonly causes chronic meningitis ?

Answer 4

Tuberculosis

Question 5

What organisms can cause aseptic meningitis ?

Answer 5

Enterovirus - coxsackievirus

Herpes simplex

Question 6

Which organisms cause acute meningitis ?

Answer 6

N.meningitidis
Streptococcus.pneumonia
Haemophilus.influenza

Question 7

Which N.meningitidis serotypes are there vaccinations for ?

Answer 7

B and C

Question 8

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

Answer 8

West Nile virus

Question 9

Name a bacterial cause of encephalitis ?

Answer 9

Listeria

Question 10

Which organisms can cause encephalitis via local invasion ?

Answer 10

Amoebae

Question 11

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

Answer 11

Toxoplasmosis- e.g toxoplasma gonadii

Question 12

What are the most common organisms responsible for brain abscesses ?

Answer 12

Streptococci

Staphylococci

Question 13

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

Answer 13

Local extension e.g from mastoiditis

Question 14

Name a common spinal infection ?

Answer 14

Pyogenic vertebral osteomyelitis

Question 15

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

Answer 15

Normal

No organisms

Question 16

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

Answer 16

Purulent meningitis (bacterial)

Meningococcus
Pneumococcus
Listeria

Question 17

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)

Answer 17

Aseptic meningitis

Coxsackie virus
Echovirus
TB

Could also be:
bacterial meningitis partially treated with ABx
Encephalitis
Brain abscess

Question 18

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)

Answer 18

Tuberculous meningitis

Mycobacterium TB

Question 19

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

Answer 19

Streptococcus. Pneumoniae

Question 20

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

Answer 20

Meningococcus (Neisseria meningitides)

Question 21

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

Answer 21

Listeria monocytogenes

Question 22

Culture and microscopy shows a positive Ziehl-Nielsen stain what organism is the likely cause of this meningitis ?

Answer 22

TB

Question 23

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 ?

Answer 23

Cryptococcus Neoformans

Question 24

Which organism commonly causes meningitis in men who have sex with men (MSM)

Answer 24

Cryptococcus Neoformans

Question 25

Which drug is effective against Meningococcus, pneumococcus, haemophilus and e.coli ?

Answer 25

Ceftriaxone I.V

Question 26

Which drug is effective at treating Listeria ?

Answer 26

Ampicillin

Question 27

Which organism is most commonly associated with recurrent aseptic meningitis (Mollaret's meningitis) ?

Answer 27

HSV-1 and HSV-2

Question 28

Which organisms are the most common cause of aseptic meningitis ?

Answer 28

Enterovirus (80%) - Echovirus, coxsackie virus

Question 29

common causes of encephalitis

Answer 29

rabies virus arboviruses prions amoeba

Question 30

common causes of myelitis

Answer 30

poiovirus

Question 31

common causes of neurotoxin release

Answer 31

clostridium tenani | clostridium botulinum

Question 32

what is meningitis

Answer 32

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)

Question 33

list other causes of meningitis

Answer 33

listeria monocytogenes group B strep E. coli rare: TB, S. Aureus, T. Pallidum, cryptococcus neoformans

Question 34

describe the processes whereby septicaemia occurs

Answer 34

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

Question 35

complications of TB meningitis

Answer 35

common in immunosuppressed complications = tuberculosis granulomas tuberculosis abscesses cerebritis there is leptomeningeal enhancement

Question 36

features of aseptic meningitis

Answer 36

``` most common infection of the CNS coxsackie group B echoviruses usually in children <1 year self-limiting, resolves in 1-2 weeks ```

Question 37

what is toxoplasmosis

Answer 37

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

Question 38

which mode of screening is best to detect parenchymal abnormalities

Answer 38

MRI better than CT to look at functional tissue

Question 39

how should CSF infections be managed

Answer 39

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