12. Bacterial Meningitis MT2 Flashcards
this is an inflammation of the cranial and spinal leptomeninges
meningitis
the meninges consist of 3 outer coverings of the brain and spinal cord which include
- Dura; inside layer tightly adherent to the cranial periosteum
- Arachnoid: middle layer that loosely covers the brain and spinal cord
- Pia Matter: outside layer that is continuous with the surface of the brain and spinal cord
cerebrospinal fluid is found in the _________ space, which is enclosed between the arachnoid and Pia matter
subarachnoid
what are the main causes of meningitis?
- bacteria
- viruses
- mycobacteria
- parasites
- fungi
true or false: meningitis can be noninfectious
true - may be drug induced or carcinomatous
the most common pathogens of bacterial meningitis are the same that colonize the mucosal surface of the respiratory tract which includes
- Streptococcus pneumoniae
- neisseria meningitidis
- haemophilus influenzae
true or false: bacteria from the GI tract, such as Listeria and group B streptococcus, can cause bacterial meningitis
true
how do the bacteria get into past the blood brain barrier in order to cause meningitis?
colonization of the mucosa occurs and the bacteria enter the bloodstream due to a break in the mucosal barrier (usually between epithelial cells)
presence of bacteria in the bloodstream allows them to invade the BBB - once the bacteria are present inside the subarachnoid space, there is little host defence
true or false: bacteria can often cause meningitis due to defects in the base of the skull, such as the cribriform plate near the ethmoid sinus
false - very rare
true or false: bacteria such as S. pneumoniae can cause meningitis from otitis media or sinusitis
true
once bacteria enter the CNS, they begin to multiply. this leads to a release of a cascade of inflammatory cytokines such as TNF-alpha and IL-1. does this increase or decrease BBB permeability
increases
release of cytokines can increase influx of _____________
granulocytes
these two infections can produce bacteria that can travel through the blood AND brain abscess in order to get to the meninges
Otitis media and Sinus infection
this type of infection can produce bacteria that can travel through the blood AND cribriform plate defect in order to get to the meninges
colonization of the nasopharynx
what do the following represent:
- brain abscess
- brain herniation
- cerebrates or ventriculitis
- CNS infarction
- diabetes insipidus
- seizure
- shock
- venous sinus thrombosis
acute complications of bacterial meningitis
what do the following represent:
- ataxia
- behavioural difficulties
- epilepsy
- hydropcephalus
- intellectual deficit
- sensorineural hearing loss
- visual problems
neurologic sequelae of bacterial meningitis
describe the clinical presentation of a child < 2 with bacterial meningitis
- may present with only a change in temperature (fever or hypothermia)
- nonspecific lethargy or LOC
- inconsolable crying or altered quality of cry, irritability, seizures, poor feeding, V/D, rash, bulging anterior fontanelle
describe the clinical presentation of older children and adults with bacterial meningitis
fever, headache, photobophobia, neck stiffness, altered mental status
this is essential for the diagnosis of bacterial meningitis
examination of the CSF for cell count, culture and sensitivity, and glucose and protein concentrations
true or false: empiric antimicrobial therapy should be delayed if a lumbar puncture can’t be performed at the time of presentation
false - empiric therapy should never be delayed
what are some instances where a lumbar puncture can not be performed? (contraindicated)
- increased intracranial pressure
- seizures
- shock or coagulopathy
- the infection is at the proposed site of lumbar puncture
will CSF be cloudy or clear if pt has bacterial meningitis
cloudy
will CSF have decreased or increased WBCs if pt has bacterial meningitis
increased WBCs
will CSF have decreased or increased glucose if pt has bacterial meningitis
decreased glucose
will CSF have decreased or increased protein if pt has bacterial meningitis
normal or elevated protein
CSF gram stain is positive in 80-90% of meningitis, but this ______________ (decreases/increases) if the patient was on antimicrobials prior to LP
decreases
what should you do if a pt. presents with papilledema and/or focal neurological deficits
- obtain a blood culture
- begin empiric antibiotics
- CT scan of head: if there is a mass lesion consult neuro, if no lesion perform LP and continue ABX
what should you do if a patient has some symptoms of meningitis but papilledema and/or focal neurological deficits are absent
- obtain and blood culture and LP stat
2a. if CSF exam = bacterial meningitis and there is a positive gram stain: start focused ABX therapy
2b. if CSF exam = bacterial meningitis but there is no gram positive stain: start empiric ABX therapy
what is a likely gram positive diplococci in BM
S. pneumoniae
what is a likely gram positive bacilli in BM
listeria
what is a likely gram negative coccobacilli in BM
haemphilius
what is a likely gram negative cocci in BM
Neisseria
S. pneumoniae, N. meningitides and H. influenzae are the expected bacterial pathogens in this age group
1 month - 50 years
S. agalactiae, E. coli, K. pneumoniae and L. monocytogenes are the expected bacterial pathogens in this age group
0-1 month
S. pneumonia, L. monocytogenes, and aerobic gram negative bacilli are the expected bacterial pathogens in this age group
> 50 years
what are some drugs that have excellent penetration into the CNS
- metronidazole
- minocycline
- TMP/SMX
- rifampin
true or false: in order for an antibiotic to work in the CNS it should be used at the max dose
true
what is the first-line regimen and alternative Tx in the 0-1month age group
first line: ampicillin + cefotaxime
alternative: ampicillin + gentamicin
what is the first-line regimen and alternative Tx in the 1 month - 50 yrs age group
first line: ceftriaxone + vancomycin + dexamethasone
alternative: meropenem + vancomycin + dexamethasone
what is the first-line regimen and alternative Tx in the >50 years age group
first line: ceftriaxone + vancomycin + ampicillin + dexamethasone
alternative: meropenem + vancomycin + dexamethasone
this medication can cause an infusion reaction, which presents like an allergic reaction, but the infusion rate just needs to be slowed
vancomycin
these are used to decrease the inflammation associated with the infection of the CNS
corticosteroids
why should corticosteroids be administered after the first dose of antibiotic
the antibiotics can access the infection in the CNS due to the inflammation caused by meningitis. decreasing the inflammation with corticosteroids may inhibit the antibiotic from getting in
corticosteroids provide beneficial effects in these two bacteria
H. influenzae type b in children and S. pneumoniae in adults
what is the duration of therapy regarding N. meningitis
7 days
what is the duration of therapy regarding H. influenzae
7 days
what is the duration of therapy regarding S. pneumoniae
10-14 days
what is the duration of therapy regarding S. agalactiae
14-21 days
what is the duration of therapy for aerobic gram negative bacilli
21 days
what is the duration of therapy for L. monocytogenes
> 21 days
how can bacterial meningitis be prevented
conjugated vaccines
this vaccine has lead to the virtual disappearance of meningitis due to that that bacteria
h. influenzae type b vaccine
this vaccine is routinely recommended for all infants
conjugated pneumococcal vaccine
this vaccine against N. meningitis is routinely recommended in all infants
conjugated meningococcal vaccine
