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Microbiology Part 1 > Lec7 Strep Pneumoniae > Flashcards

Lec7 Strep Pneumoniae Flashcards

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1
Q

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

A

gram positive

encapsulated diplocci

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2
Q

How do you identify s. pneumonia?

A
  • gram +
  • encapsulated diplocci
  • alpha hemolytic
  • no lancefield antigen
  • optochin sensitive
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3
Q

What are risk factors for pneumonia?

A
  • transmission through respiratory droplets
  • overcrowding, day care, smoking
  • age [60]
  • immunosuppression
  • csf leaks
  • cochlear implants
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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
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5
Q

What are the symptoms of pneumonia?

A
  • fever
  • cough
  • sputum
  • dyspnea
  • pleuritic chest pain
  • consolidation on exam and CXR
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6
Q

What is meningitis?

A

pneumococcus nfection in subarachnoid space

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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

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8
Q

What are signs of otitis media?

A
  • fever, earache
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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
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10
Q

What are possible complications of otitis media?

A
  • usually self limited

- can lead to hearing loss, mastoiditis, meningitis

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11
Q

What causes sinusitis?

A
  • pneumoccocus
  • or other bacteria [haemphilus influenza, moraxella catarrhalis]
  • or virus
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12
Q

What is the main virulence factor of pneumococcus?

A

the capsule

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13
Q

What mediates pneumococcus binding? What can counteract it?

A
  • mediated by surface adhesion
  • counteracted by secretory IgA
  • pneumococci can produce IgA protease
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14
Q

How is pneomococcus spread?

A
  • by contiguity [lungs, sinus, ears]

- through blood stream [meningitis, endocarditis, arthritis]

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15
Q

What is mech of capsule evading phagocytosis?

A
  • prevents mechanical clearance by mucosa

- interferes with complement

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16
Q

What happens if pneumococcus has no capsule?

A

get no disease

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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
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18
Q

What is IgA protease?

A

virulence factor of pneumococcus

- breaks down IgA that is trying to inhibit pneumococcus binding

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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

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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
Q

What is drug of choice for listeria?

A

ampicillin

26
Q

Is meningitis caused by listeria treatable by cephalosporins?

A

No – you have to use ampicillin

27
Q

what are some times when ceftatrioxe is not good choice

A
  • 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
Q

Is ceftriaxone IV/IM or oral?

A

IV/IM only

29
Q

How long is ceftriaxone half life? how frequent dosing?

A
  • long half life

- once daily dosing

30
Q

Does ceftriaxone penetrate blood-brain barrier?

A

yes

31
Q

How is ceftriaxone excreted? significance?

A
  • secreted via bile
  • thus does not require renal adjustment
  • but also means it can cause biliary sludging so not good for newborns
32
Q

What are possible side effects of ceftriazone?

A
  • allergy [rash –> anaphylaxis]

- some cross-rxn with penicillin

33
Q

How does cefotaxime differ from ceftriaxone?

A
  • shorter half life so need more frequent dosing

- excreted by kidneys so preferable for newborns and those with underlying liver disease

34
Q

What are the three fluoroquinolones?

A
  • ciprofloxacin
  • levofloxacin
  • mocifloxacin
35
Q

What do the fluoroquinolones treat?

A

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
Q

which fluroquinolones treat gram neg? gram pos? anaerobes? atypicals?

A

gram -: all 3 [cipro, levo, moxi]

gram +: levo and moxi

anaerobes: only moxi

atypicals [mycoplasma, chlamydia, legionella]: all 3 [cipro, levo, moxi]

37
Q

What is the preferred fluoroquinolone for respiratory infection?

A

levofloxacin

38
Q

Will ciprofloxacin treat respiratory infections?

A

not good choice because no reliable activity against gram + organisms

39
Q

What is mech of fluoroquinolone action [action, bioavailability, half life, CNS penetration]?

A
  • inhibit bacterial DNA synthesis by inhibitng topoisomerase and DNA gyrase
  • 100% bioavailability
  • long half life
  • good CNS penetration
40
Q

What are side effects of fluoroquinolones?

A
  • GI intolerance
  • dizziness/headache
  • tenodonitis and tendone rupture
  • GTc interval prolongation
41
Q

Are fluoroquinolones okay for kids?

A
  • not used in kids unless other alternative not available
42
Q

What is the empiric treatment of bacterial meningitis? why?

A
  • vancomycin and ceftriaxone

- use both in case it is resistant to beta-lactams

43
Q

What does vancomycin act against? oral or IV?

A

IV only

active only against gram pos

44
Q

What is empiric treatment of otitis media and sinusitis?

A

oral amoxicillin

main organism is s. pneumoniae

45
Q

What is empiric treatment for pneumonia?

A
  • amoxocillin [oral]
  • azithromycin [oral]
  • ceftriaxone [IV] (+/- azithromycin)
  • levofloxacin [IV or oral]
46
Q

What is pneumovax?

A
  • vaccine against 23 serotypes of pneumococcus
  • not immunogenic in children under 2 because T cell dependent
  • made of purified capsule antigens
47
Q

What is PCV13 [Prevnar-13]?

A
  • vaccine against capsular polysaccharide from 13 serotypes

- made of capsular polysaccharides conjugated to mutant diphtheria toxoid

48
Q

How can you prevent pneumococcus besides vaccines?

A
  • chemoprophylaxis with penicillin

Microbiology Part 1 (24 decks)

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