IC17 Community acquired bacterial meningitis

Question 1

risk factors/ predisposing factors

TIC2S

Answer 1

1. immunocompromised
2. prolonged contact with infected individuals
3. travel to endemic areas
4. CNS shunting: tube draining CSF from brain due to fluid buildup
5. splenectomised patients
   * Removal of spleen due to its enlargement will compromise immunity ⇒ important to be vaccinated to prevent bacterial infections
   * Spleen = important for immunity against bacterial infection; have macrophages that neutralise bacteria

Question 2

mechanisms of entry

Answer 2

Invasion of mucosal surface
* Bacteria transported in blood to meninges

Spread from para-meningeal focus
* Organs nearby affected organ can get infected by bacteria
* Local infections → sinusitis, otitis media, pharyngitis

Head trauma
* Direct inoculation of bacteria onto meninges from external due to opening of meninges

Anatomical defects
* Bacteria can colonise & invade; Multiplication of bacteria ⇒ infection
* CSF fistula/ leak
Fistula → abnormal connection between tissues
Leak → break in mucosa (supposedly closed)
* Congenital defects → structural damage protecting tissues; allows spread of bacteria

Neurological procedures
Bacteria introduced during surgery

Question 3

symptoms

Answer 3

• Fever, chills
• Classic triad: headache, backache, nuchal (neck) rigidity
• Mental status change (irritability), photophobia
• N/V, anorexia, poor feeding habits (infants)
• petechiae/ purpura ⇒ neisseria meningitidis meningitis infection

Question 4

physical signs

Answer 4

Kernig sign
When hamstring extended & thigh is perpendicular to trunk ⇒ severe back pain

Brudzinski sign
* Severe neck stiffness
* When neck held up, hip & knee will naturally move up

Building fontane
* Occurs in children
* Skull does not close up due to inflammation (alot of CSF & inflammatory processes)

Question 5

diagnostic methods

Answer 5

1. hx & physical examination
2. blood culture
3. lumbar puncture
4. general lab tests
5. radiology (brain CT scan/ MRI)

Question 6

diagnostic: lumbar puncture

what can be derived, continuation of empiric therapy

Answer 6

CSF composition, gram-stain, culture & PCR (to check for genetic material)
Suggestive, but do not confirm aetiology of meningitis

To continue empiric therapy until CSF culture becomes negative + no other evidence of bacterial infection

Question 7

p

diagnostic: lumbar puncture
composition of normal CSF

glucose, protein, WBC

Answer 7

Glucose
2.6-4.5 mmol/L
CSF : blood > 0.66

Protein
< 0.4 g/L

WBC
< 5 cells/ mm3

Question 8

diagnostic: lumbar puncture
composition of bacterial meningitis

glucose, protein, WBC

Answer 8

Glucose
Very low
CSF : blood < 0.4 (Due to bacteria consuming glucose)

Protein
Raised; >1.5 g/L

WBC
Raised; > 100 cells/ mm3
Predominantly neutrophils; for pleocytosis

Question 9

diagnostic: lumbar puncture
composition of viral meningitis

glucose, protein, WBC

Answer 9

Glucose
Normal to slightly low

Protein
Normal to mildly raised

WBC
Raised; 5-1000 cells/ mm3
Predominantly lymphocytes; to clear virus

Question 10

diagnostic: general lab test

Examples

Answer 10

WBC, C-reactive protein, procalcitonin

Question 11

diagnostic: radiology

indications, when to conduct

Answer 11

Usually for:
* Evaluation of differential diagnosis & complications
* If patient conscious level is low/ not alert

Can be done before lumbar punctures in patients with concerns of brain shift due to mass lesion (extremely swollen brain)
* Due to risk of brain herniation (dropping of tissues) during lumbar puncture

Question 12

causative pathogens: neonates (<1 month)

Answer 12

Group B streptococcus (streptococcus agalactiae)
E.coli
Listeria monocytogenes

Question 13

causative pathogens: infants-children (1-23 months)

Answer 13

Streptococcus pneumoniae
Neisseria meningitidis
Group B Streptococcus (S. agalactiae)
E.coli

Question 14

causative pathogens: children-adults (2-50 years)

Answer 14

S.pneumoniae
N. meningitidis

Question 15

causative pathogens: adults (>50 years)

Answer 15

S.pneumoniae
N. meningitidis
L. monocytogenes
Aerobic gram-negative bacilli: E.coli, Klebsiella species

Question 16

causative pathogens: Listeria Monocytogenes

characteristics, common infectees, where it is found

Answer 16

• Gram-positive, intracellular rod bacteria
• Commonly infected elderly & young ⇒ weaker immune system; unable to clear bacteria
• Found in moist environment, soil & water
• Linked to food-borne disease outbreaks
  ie: cold deli meats & unpasteurised dairy products
• Can grow & replicate in refrigerator temperature

Question 17

causative pathogen: Neisseria meningitidis

characteristics, location

Answer 17

• Fastidious, encapsulated, aerobic gram-negative diplococcus
• Exists in nasopharynx of healthy individuals

Question 18

empiric therapy: when to start

Answer 18

ASAP, within 1 hour

Question 19

empiric therapy: neonates

Answer 19

Ceftriaxone + ampicillin

Question 20

empiric therapy: infants-children

Answer 20

Ceftriaxone + vancomycin

Question 21

empiric therapy: children-adult

Answer 21

Ceftriaxone + vancomycin

Question 22

empiric therapy: >50 year old

Answer 22

Ceftriaxone + vancomycin + ampicillin

Question 23

culture-directed therapy: ROA

Answer 23

All IV treatment → to ensure high serum concentration of drug enters CSF

Question 24

culture-directed therapy: s. pneumoniae

drugs & duration

Answer 24

10-14 days

Penicillin susceptible: Penicillin G or Ampicillin

Penicillin resistant, cephalosporin susceptible:
Ceftriaxone

Penicillin & cephalosporin resistant:
Vancomycin + rifampicin

Question 25

culture-directed therapy: listeria monocytogenes | drugs & duration

Answer 25

≥ 21 days **Penicillin susceptible:** Penicillin G or Ampicillin **Penicillin allergy:** co-trimoxazole, meropenem

Question 26

culture-directed therapy: Neisseria Meningitidis | drugs & duration

Answer 26

5-7 days **Penicillin susceptible:** Penicillin G or Ampicillin **Penicillin resistant, cephalosporin susceptible:** Ceftriaxone

Question 27

culture-directed therapy: grp B strep | drugs & duration

Answer 27

14-21 days **Penicillin susceptible:** Penicillin G or Ampicillin **Penicillin resistant, cephalosporin susceptible:** Ceftriaxone

Question 28

adjunctive therapy: dexamethasone | indication

Answer 28

Recommended for patients with bacterial meningitis > 6 weeks old (beyond neonatal age) Due to severe inflammation of subarachnoid space Key bacteria for initiation: **H.influenzae** & **S.pneumoniae**

Question 29

adjunctive therapy: dexamethasone

Answer 29

Recommended for patients with bacterial meningitis > 6 weeks old (beyond neonatal age) Due to severe inflammation of subarachnoid space **Key bacteria for initiation:** H.influenzae & S.pneumoniae

Question 30

adjunctive therapy: dexamethasone | benefits

Answer 30

* Less hearing loss & other neurologic sequelae in H.influenzae & S.pneumoniae meningitis * Decreased mortality in S.pneumoniae meningitis

Question 31

adjunctive therapy: dexamethasone | risks

Answer 31

May **decrease AB penetration** * Meningitis = inflammation of meninges; allows for more AB to enter * Reduction of inflammation ⇒ lesser drugs can enter **ADR**: mental status changes (ie: delirium), hyperglycemia, hypertension

Question 32

adjunctive therapy: dexamethasone | dosing instructions

Answer 32

Administer 10-20 mins before OR at same time as first dose of AB * AB kills bacteria; releases substances that can cause more significant inflammation * Dexamethasone ⇒ prophylaxis to control inflammation Dexamethasone 10 mg q6h up to 4 days [adult dose] Stop if patient discovered not to have bacterial meningitis OR if bacterium causing meningitis is not H.influenzae or S.pneumoniae

Question 33

AB dosing | ampicillin, penG, ceftriaxone, vanco, rifampicin, meropenem

Answer 33

1. IV 2g q4h 2. IV 4MU q4h 3. IV 2g q12h 4. IV 25-30mg/kg q8-12h 5. IV 300mg q12h 6. IV 2g q8h

Question 34

AB to caution/ avoid

Answer 34

* **Imipenem & fluoroquinolones** at high doses ⇒ may cause seizures * **cefepime** in patients on dialysis → must properly adjust for renal dosing No proper adjustments ⇒ may cause accumulation in blood & seizures * All **b-lactam** at supratherapeutic levels ⇒ may be neurotoxic

Question 35

prophylaxis for meningococcal meningitis indication | key bacteria, individuals

Answer 35

Key bacteria: Neisseria meningiditis close contacts & exposure to oral secretions of infected individuals

Question 36

prophylaxis for meningococcal meningitis drug choice

Answer 36

**Rifampicin** ⇒ total 2 days therapy * Adults: 600 mg q12h, 4 doses * Children: 10 mg/kg q12h, 4 doses * Infants (<1 month): 5 mg/kg q12h, 4 doses **Ciprofloxacin**: PO 500 mg, 1 dose ⇒ only for adults Not for children due to arthropathy risk **Ceftriaxone**: IM 125-250 mg, 1 dose