Microbiology - CNS infections

Question 1

How does pyogenic meningitis appear macroscopically?

Answer 1

Shows a thick layer of suppurative exudate covering the leptomeninges over the surface of the brain

Question 2

How does pyogenic meningitis appear microscopically?

Answer 2

There are neutrophils in the subarachnoid space

Question 3

What are some of the causative organisms of community acquired bacterial meningitis?

Answer 3

Pneumococcus, meningococcus, Haemophilus influenzae, listeria (if >60y/o)

Question 4

How is bacterial meningitis treated?

Answer 4

IV ceftriaxone 2g BD (or chloramphenicol if allergic) + IV dexamethasone 10mg QDS for 10 days

Question 5

If listeria cover is required how is bacterial meningitis treated?

Answer 5

IV Amoxicillin/ampicillin 2g 4 hourly (or co-trimoxazole if allergic)

Question 6

If penicillin resistant pneumococci cover is required how is bacterial meningitis treated?

Answer 6

IV Vancomycin or IV/PO rifampicin

Question 7

What is the most common cause of viral meningitis?

Answer 7

Enteroviruses e.g. ECHO virus

Question 8

How is viral meningitis diagnosed?

Answer 8

viral stool culture, throat swab and CSF PCR

Question 9

How is viral meningitis treated?

Answer 9

Generally supportive as self-limiting

Question 10

How is viral encephalitis treated?

Answer 10

14 days IV aciclovir or 21 days if immunocompromised

Question 11

What are some of the clinical features of encephalitis?

Answer 11

Insidious onset, meningismus, stupor, seizures, confusion, psychosis, speech and memory problems

Question 12

How is encephalitis diagnosed?

Answer 12

LP, EEG, MRI

Question 13

What are some of the clinical features of meningitis?

Answer 13

Fever, rash, severe headache, neck stiffness, photophobia, vomiting, drowsiness, confusion, severe muscle pain, convulsions

Question 14

What bacterial meningitis causing organisms are neonates most susceptible to?

Answer 14

Listeria, group B strep, E.coli

Question 15

What bacterial meningitis causing organisms are children most susceptible to?

Answer 15

Haemophilus influenzae

Question 16

What bacterial meningitis causing organisms are adolescents most susceptible to?

Answer 16

Neisseria meningitidis

Question 17

What bacterial meningitis causing organisms are adults most susceptible to?

Answer 17

Strep. pneumoniae, neisseria meningitidis

Question 18

What bacterial meningitis causing organisms are elderly people most susceptible to?

Answer 18

Strep. pneumoniae, listeria

Question 19

What bacterial meningitis causing organisms are people with head trauma or post-neurosurgery most susceptible to?

Answer 19

Staph aureus, staph epidermidis, aerobic gram negative bacilli

Question 20

What bacterial meningitis causing organisms are immunocompromised people most susceptible to?

Answer 20

Strep pneumoniae, neisseria meningitidis, listeria, aerobic GNB

Question 21

What bacterial meningitis causing organisms are people with a basilar skull fracture most susceptible to?

Answer 21

Strep pneumoniae, H.influenzae, GABHS

Question 22

Which cranial nerves are most susceptible to exudate as a complication of bacterial meningitis?

Answer 22

CNs III, VI

Question 23

What are the 3 methods of pathogenesis of bacterial meningitis?

Answer 23

1. Nasopharyngeal colonisation
2. Direct extension of bacteria e.g. mastoiditis
3. From remote foci of infection e.g. pneumonia

Question 24

How does tuberculous meningitis occur and who is most at risk?

Answer 24

Due to reactivation of TB

Most common in elderly

Question 25

How is tuberculous meningitis treated?

Answer 25

Isoniazid and rifampicin (+pyrazidamole, ethambutol)

Question 26

What are the features of cryptococcal meningitis?

Answer 26

Fungal
Mainly in HIV patients
CD4<100
Aseptic picture on CSF

Question 27

How is cryptococcal meningitis treated?

Answer 27

IV amphotericin B/ flucytosine

Fluconazole

Question 28

What type of organism is Haemophilus influenzae?

Answer 28

Gram negative rods/coccobacilli

Question 29

What percentage of bacterial meningitides are culture negative?

Answer 29

10-15%

Question 30

What are the distinguishing features of viral meningitis on CSF?

Answer 30

10-1000 lymphocytes predominantly, everything else is usually normal, except the protein can be slightly raised

Question 31

What are the distinguishing features of bacterial meningitis on CSF?

Answer 31

10-10,000 polymorphs (neutrophils) predominantly, positive gram stain, high protein and <70% of blood glucose

Question 32

What are the distinguishing features of tuberculous meningitis on CSF?

Answer 32

10-1000 lymphocytes predominantly, +/- gram stain, high or very high protein and <60% of blood glucose

Question 33

What is aseptic meningitis?

Answer 33

Non-pyogenic bacterial meningitis
CSF - low WCC, slightly raised protein, normal glucose
Much bigger differential than viral meningitis

Question 34

What are some of the treatable causes of aseptic meningitis?

Answer 34

HSV 1 + 2, syphilis, listeria, TB, carcinomatous, sarcoidosis, vasculitis, migraine

Question 35

Who should undergo a CT scan prior to LP?

Answer 35

Immunocompromised patients, history of CNS disease, new onset seizure, papilloedema, abnormal level of consciousness, focal neurological deficit

Question 36

Should antibiotics be given before or after a LP?

Answer 36

Immediately after a LP but if the LP will be delayed >30mins then give IV antibiotics first

Question 37

How should people who have been in contact with meningitis be prophylactically treated?

Answer 37

600mg PO rifampicin 12 hourly for 4 doses OR
500mg PO cirprofloxacin as a single dose OR
250mg IM ceftriaxone as a single dose (125mg IV for children)

Question 38

What should people given rifampicin be warned of?

Answer 38

Reduced efficacy of oral contraceptives, red colouration of urine and staining of contact lenses

Question 39

What vaccines are available for meningitis?

Answer 39

Neisseria meningitis, H. influenzae and strep pneumoniae