Lec7 Strep Pneumoniae Flashcards

1
Q

What is shape of strep pneumoniae? gram + or -?

A

gram positive

encapsulated diplocci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do you identify s. pneumonia?

A
  • gram +
  • encapsulated diplocci
  • alpha hemolytic
  • no lancefield antigen
  • optochin sensitive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are risk factors for pneumonia?

A
  • transmission through respiratory droplets
  • overcrowding, day care, smoking
  • age [60]
  • immunosuppression
  • csf leaks
  • cochlear implants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How are serotypes categorized?

A
  • more than 90 exist
  • based on capsular polysaccharide
  • vary by geo location
  • means hard to have single vaccine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the symptoms of pneumonia?

A
  • fever
  • cough
  • sputum
  • dyspnea
  • pleuritic chest pain
  • consolidation on exam and CXR
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is meningitis?

A

pneumococcus nfection in subarachnoid space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are symptoms and 3 signs of meningitis?

A

symptoms
- fever
- photophobia
- headache
- altered mental status
3 signs
- nuchal rigidity: neck stiffness, inability to flex neck forward
- kernig sign: bend the thigh at the hip and knee at 90 degree angles, positive if it is then very painful/difficult to extend the knee
- brudzinsky sign: positive if when someone is lying down and you lift their head they have involuntary hip and knee flexion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are signs of otitis media?

A
  • fever, earache
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what causes otitis media?

A
  • by pneumococcus
  • or by other bacteria [haemphilus influenzae, moraxella catarrhalis]
  • or by virus
    most severe if caused by pneumococcus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are possible complications of otitis media?

A
  • usually self limited

- can lead to hearing loss, mastoiditis, meningitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What causes sinusitis?

A
  • pneumoccocus
  • or other bacteria [haemphilus influenza, moraxella catarrhalis]
  • or virus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the main virulence factor of pneumococcus?

A

the capsule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What mediates pneumococcus binding? What can counteract it?

A
  • mediated by surface adhesion
  • counteracted by secretory IgA
  • pneumococci can produce IgA protease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is pneomococcus spread?

A
  • by contiguity [lungs, sinus, ears]

- through blood stream [meningitis, endocarditis, arthritis]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is mech of capsule evading phagocytosis?

A
  • prevents mechanical clearance by mucosa

- interferes with complement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens if pneumococcus has no capsule?

A

get no disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is pneumolysin?

A
  • virulence factor of pneumococcus released from cell
  • cytotoxic to phagocytic cells
  • cytotoxic to respiratory epithelial cells
  • increases TNF-a and IL-1 secretion which triggers inflammatory cascade
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is IgA protease?

A

virulence factor of pneumococcus

- breaks down IgA that is trying to inhibit pneumococcus binding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is pneumococcus immunity specific for? What organ system regulates pneumococcus immunity?

A
  • capsular type specific immunity

- lymphoreticular system –> main place where phagocytosis to take place in spleen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is functional or anatomic asplenia a risk factor for?

A
  • risk factor for overwhelming infection with encapsulated organisms since spleen is place where phagocytosis of bugs primarily occurs
21
Q

What is most effect treatment for most pneumococcus infections?

A
  • beta lactams
22
Q

what is the mech of beta-lactam resistance in pneumococcus? what does this mean for use of beta-lactamase inhibitors?

A
  • resistance by altering penicillin binding proteins [PBP]
  • thus does not use betalactamases
  • betalactamase inhibitors [clavulinic acid, sulbactam] will not help
23
Q

What 4 beta lactams are primarily used to treat pneumococcus?

A

penicillins:
amoxicillin [oral]
ampicillin [IV]

for sicker patients use gen 3 cephalosporins:
cefotaxime
ceftriaxone

24
Q

What can cetriaxone treat?

A
  • gram + or gram -
  • gets into CSF
  • good activity against 3 most common causes of meningitis [s. pneumoiae, n. meningitidis, H influenzae]
25
What is drug of choice for listeria?
ampicillin
26
Is meningitis caused by listeria treatable by cephalosporins?
No -- you have to use ampicillin
27
what are some times when ceftatrioxe is not good choice
- not as good for MSSA as anti-stpah penicillins or 1st gen cephalosporins - can't treat MRSA, enterococcus, listeria, psueomonas, nonsocomial gram neg, anaerobes
28
Is ceftriaxone IV/IM or oral?
IV/IM only
29
How long is ceftriaxone half life? how frequent dosing?
- long half life | - once daily dosing
30
Does ceftriaxone penetrate blood-brain barrier?
yes
31
How is ceftriaxone excreted? significance?
- secreted via bile - thus does not require renal adjustment - but also means it can cause biliary sludging so not good for newborns
32
What are possible side effects of ceftriazone?
- allergy [rash --> anaphylaxis] | - some cross-rxn with penicillin
33
How does cefotaxime differ from ceftriaxone?
- shorter half life so need more frequent dosing | - excreted by kidneys so preferable for newborns and those with underlying liver disease
34
What are the three fluoroquinolones?
- ciprofloxacin - levofloxacin - mocifloxacin
35
What do the fluoroquinolones treat?
specific to each drug but overall do: - gram negatives including pseudomonas - gram + but not MRSA/enterococcus consistently [not cipro] - anaerobes [only moxi] - atypicals [mycoplasma, chlamydia, legionella]
36
which fluroquinolones treat gram neg? gram pos? anaerobes? atypicals?
gram -: all 3 [cipro, levo, moxi] gram +: levo and moxi anaerobes: only moxi atypicals [mycoplasma, chlamydia, legionella]: all 3 [cipro, levo, moxi]
37
What is the preferred fluoroquinolone for respiratory infection?
levofloxacin
38
Will ciprofloxacin treat respiratory infections?
not good choice because no reliable activity against gram + organisms
39
What is mech of fluoroquinolone action [action, bioavailability, half life, CNS penetration]?
- inhibit bacterial DNA synthesis by inhibitng topoisomerase and DNA gyrase - 100% bioavailability - long half life - good CNS penetration
40
What are side effects of fluoroquinolones?
- GI intolerance - dizziness/headache - tenodonitis and tendone rupture - GTc interval prolongation
41
Are fluoroquinolones okay for kids?
- not used in kids unless other alternative not available
42
What is the empiric treatment of bacterial meningitis? why?
- vancomycin and ceftriaxone | - use both in case it is resistant to beta-lactams
43
What does vancomycin act against? oral or IV?
IV only | active only against gram pos
44
What is empiric treatment of otitis media and sinusitis?
oral amoxicillin main organism is s. pneumoniae
45
What is empiric treatment for pneumonia?
- amoxocillin [oral] - azithromycin [oral] - ceftriaxone [IV] (+/- azithromycin) - levofloxacin [IV or oral]
46
What is pneumovax?
- vaccine against 23 serotypes of pneumococcus - not immunogenic in children under 2 because T cell dependent - made of purified capsule antigens
47
What is PCV13 [Prevnar-13]?
- vaccine against capsular polysaccharide from 13 serotypes | - made of capsular polysaccharides conjugated to mutant diphtheria toxoid
48
How can you prevent pneumococcus besides vaccines?
- chemoprophylaxis with penicillin