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IP-10 Final Exam > CNS infections > Flashcards

CNS infections Flashcards

1
Q

Difference between meningitis and encephalitis (bacteria or virus)

A

Meningitis: Inflammation of the meninges and subarachnoid space caused by bacteria.
Aseptic meningitis: Non-bacterial causes
Encephalitis: Inflammation on the brain typically caused by a virus.

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2
Q

Define the meninges and the fluid filled spaced between them

A

Meninges: Pia, arachnoid and dura mater

Subarachnoid space is the space between the arachnoid and pia mater

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3
Q

What 3 mechanisms do the brain use to control its composition

A

BBB, CSF formation, Glial cell conditioning

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4
Q

List the components of the BBB

A

It is the physical barrier that prevents diffusion of disruptive substances from the blood into the brain extracellular fluid. Tight junctions join adjacent cells along the length of the brain capillaries.

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5
Q

What are the 3 communication barriers between the blade and the brain extracellular fluid

A

The presence of think basement membrane that coats endothelial cells, processes/endfeet of astrocytes continuously covers the capillary, parasites in the basement membrane modulate endothelial and astrocytic functions.

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6
Q

Explain how CSF is formed and the pathway of the CSF through circulation

A

CSF is formed by the choroid plexus. From the choroid plexus, CSF circulates through the ventricles, enters the subarachnoid space, and exits into the venous system. Choroid plexus tightly regulates CSF composition.

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7
Q

What are the 5 functions of astrocytes

A

Produce and deliver nutrients to neurons, regulate extracellular K+ levels, synthesize and recycle NT, promote survival of neurons by secreting trophic factors, form the BBB

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8
Q

What are the 2 functions of oligodendrocytes

A

Myelinate neuronal axons and regulate pH and iron metabolism

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9
Q

What are the 2 functions of microglia

A

Phagocytose bacteria and damaged cells, present antigen to T cell

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10
Q

How can infectious pathogens enter the CNS (4 methods)

A
  1. Carried in the blood (hematogenous spread)
  2. direct implantation through trauma or congenital malformations
  3. infected tooth or sinuses spreading to CNS
  4. transport along peripheral nervous system
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11
Q

Explain the mechanism by which pathogens cause damage to the CNS

A

Directly from pathogen, indirectly from microbial toxins, inflammatory mediators and immune-mediated mechanisms
Damaged endothelium can result in ischemic necrosis

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12
Q

Most common bacterial etiologies in < 1 month, 1-23 months, 2-50 years, >50 years, immunocompromised, any age with penetrating head trauma or infection of neurosurgery)

A

<1 month: S. agal, E. coli, Listeria
1-23 months: S, agal, E. coli, H. influenzawe, S. pneumo, N. meningitidis
2-50 years: S. pneumo, N. meningitidis
>50 YO: S. pneumo, N. menin, Listeria, E. coli
Immunocompromised: Listeria
Head trauma: S. aureus, P. aeruginosa

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13
Q

Explain the staining characteristics of S. agal, E. coli, Listeria, H. influenzae, S. pneuma and N. meningitidis

A

S. agal: Gram-pos Cocci in pairs (B-hemo)
E. coli: GNR (lactose positive)
Listeria: Gram-pos rods
H. influenzae: GNR
S. pneumo: gram pos diplococci (a-hemolytic)
N. meningitidis: Gram neg cocci

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14
Q

Clinical presentation of bacterial meningitis

A

Infants: Irritability, altered eating/sleeping patterns, crying, vomiting, seizures
95% of patients will have 2 of the following 4 symptoms: Fever, stiff neck, altered MS, HA
Other symptoms: Photophobia, N/V, seizures

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15
Q

What are the 2 specific signs of meningitis

A

Kernigs: Inability to straighten knee from bent position
Brudzinskis: Severe neck stiffness causing hips and knees to flex when head is fixed

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16
Q

What are the 4 goals of therapy for the treatment of meningitis?

A

Start prompt empiric therapy, improve signs and symptoms, eradicate infection, prevent development of neurological sequelae

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17
Q

What is the appropriate empiric therapy for most patients (non immunocompromised, and between the ages of 1 month and 50 years)

A

3rd gen ceph (Ceftriaxone or cefotaxmine) + Vanco with or without rifampin

18
Q

What is the appropriate empiric therapy for those < 1 month, >50 years or immunocompromised

A

3rd gen ceph (Ceftriaxone or cefotamine) + Vanco + Ampicillin with or without rifampin

19
Q

In which patient population should ceftriaxone be avoided and why

A

Avoid in hyperbilirubinemic neonates (< 1 month) and should not be given with IV calcium containing products in neonates because risk of calcium deposition in organs

20
Q

How long should empiric therapy continue?

A

At least 2-3 days or until diagnosis of bacterial meningitis is ruled out

21
Q

When should gentamicin be added to treatment regimens?

A

Infants < 1 month of age

22
Q

What are the appropriate doses of cefotaxime, ceftriaxone, vancomycin and ampicillin

A

Ceftriaxone 2 grams Q 12 H
Cefotaxime 2 grams Q 4-6 H
Vanco 15mg/kg (target trough 15-20)
Ampicillin 2 grams Q 4 H

23
Q

Which microbial pathogens commonly seen in are covered by ceftriaxone, cefotaxime, vanco, and ampicillin

A

Ceftriaxone: S. pneumo, H. influenzae, N. meningitidis
Cefotaxime: Same as ceftriaxone
Vanco: Extensive gram + coverage (S. pneumo, S. agal)
Ampicillin: Drug of choice for Listeria and susceptible strains of N. meningitidis and H. influenzae

24
Q

For the third generation cephalosporins, which MIC values for S. pneumo correlate to resistant, susceptible and intermediate

A

MIC < 0.5 = Susceptible
MIC 1 = intermediate
MIC > 2 resistant

25
Q

Appropriate antibiotic and duration of treatment for S. pneumo

A

10-14 days.
If sensitive to 3rd gen= 3rd gen monotherapy
If resistant= 3rd gen + vanco

26
Q

Appropriate antibiotic and duration of treatment for N. meningitidis

A

7 days
If sensitive to ampicillin= ampicillin or PCN monotherapy
If resistant to ampicillin= 3rd gen monotherapy

27
Q

Appropriate antibiotic and duration of treatment for H influenzae

A

7 days
If sensitive to ampicillin=ampicillin mono therapy
If resistant to ampicillin=3rd gen monotherapy

28
Q

Appropriate antibiotic and duration of treatment for S. agalactiae

A

14-21 days with ampicillin or penicillin with or without aminoglycoside

29
Q

Appropriate antibiotic and duration of treatment for E. coli

A

21 days with 3rd gen monotherapy

30
Q

Appropriate antibiotic and duration of treatment for Listeria

A

> 21 days with ampicillin or penicillin mono therapy with or without aminoglycoside

31
Q

What is the role of steroids in the treatment of meningitis

A

Dexamethasone most commonly used to reduce the incidence of neurologic sequelae. They prevent neuronal tissue damage via reduction in inflammation and swelling.

32
Q

How should dexamethasone be administered for the treatment of meningitis

A

IV dexamethasone should be started 15-20 mins before OR at the same time as the first dose of antibiotic at a dose of 0.15mg/kg (10mg in adults) Q 6 hours X 4 days.

33
Q

What are the 4 principles of treatment for bacterial meningitis

A

Use high dose IV therapy, agent needs to penetrate the BBB, agent needs to be bactericidal in the CSF, agents must cover the identified organisms causing the disease.

34
Q

When should rifampin be added to treatment regimens?

A

Some clinicians add rifampin whenever dexamethasone is used in order to ensure adequate CSF penetration of Abx.

35
Q

State the role of chemoprophylaxis and identify if prophylaxis in indicated

A

Patients in close contact with meningitis caused by N. meningitidis or H. influenzae are at an increased risk of contracting bacterial meningitis. Close contact is >8 hours/day in close proximity < 3 feet OR anyone who had been directly exposed to infected patients oral secretions from 1 week prior to onset of symptoms until 24 hours after the patient has received treatment.

36
Q

Recommend appropriate drugs used for prophylaxis against N. meningitidis and H. infleunzae

A

N. meningitidis: Rifampin, cipro (adults only), ceftriaxone IM 1 dose
H. influenzae: Rifampin

37
Q

What vaccines can be used to prevent meningitis

A

Pneumonia (S. pneumo)
Hib (H. influenzae)
Meningococcal (n. meningitidis)
Recombinant meningitis vaccine that protects against serotype B

38
Q

Which specific meningitis vaccines can be used in certain ages?

A

Menomune: ages 2 and above
Menveo: 2 months-55 years
Menactra: 9 months-55 years

39
Q

What are the causes of ascetic meningitis

A 
Cryptococcal meningitis (fungal): Usually occurs in patients co-infected with HIV and CD4 count < 50.
Viral: West nile, MMR, polio, varicella,zoster, HIV.
Medication induced: NSAIDs, B-lactams, sulfa drugs, IVIG
40
Q

What is the recommended treatment for ascetic meningitis?

A

Supportive care.
Herpes simplex virus is the exception and it should be treated with IV acyclovir 10mg/kg (IBW for obese patients)
If medication induced patient should d/c the offending agent

41
Q

Where is CSF resorbed?

A

At the arachnoid villi

IP-10 Final Exam (5 decks)

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