Lec7 Strep Pneumoniae Flashcards
What is shape of strep pneumoniae? gram + or -?
gram positive
encapsulated diplocci
How do you identify s. pneumonia?
- gram +
- encapsulated diplocci
- alpha hemolytic
- no lancefield antigen
- optochin sensitive
What are risk factors for pneumonia?
- transmission through respiratory droplets
- overcrowding, day care, smoking
- age [60]
- immunosuppression
- csf leaks
- cochlear implants
How are serotypes categorized?
- more than 90 exist
- based on capsular polysaccharide
- vary by geo location
- means hard to have single vaccine
What are the symptoms of pneumonia?
- fever
- cough
- sputum
- dyspnea
- pleuritic chest pain
- consolidation on exam and CXR
What is meningitis?
pneumococcus nfection in subarachnoid space
what are symptoms and 3 signs of meningitis?
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
What are signs of otitis media?
- fever, earache
what causes otitis media?
- by pneumococcus
- or by other bacteria [haemphilus influenzae, moraxella catarrhalis]
- or by virus
most severe if caused by pneumococcus
What are possible complications of otitis media?
- usually self limited
- can lead to hearing loss, mastoiditis, meningitis
What causes sinusitis?
- pneumoccocus
- or other bacteria [haemphilus influenza, moraxella catarrhalis]
- or virus
What is the main virulence factor of pneumococcus?
the capsule
What mediates pneumococcus binding? What can counteract it?
- mediated by surface adhesion
- counteracted by secretory IgA
- pneumococci can produce IgA protease
How is pneomococcus spread?
- by contiguity [lungs, sinus, ears]
- through blood stream [meningitis, endocarditis, arthritis]
What is mech of capsule evading phagocytosis?
- prevents mechanical clearance by mucosa
- interferes with complement
What happens if pneumococcus has no capsule?
get no disease
What is pneumolysin?
- 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
What is IgA protease?
virulence factor of pneumococcus
- breaks down IgA that is trying to inhibit pneumococcus binding
What is pneumococcus immunity specific for? What organ system regulates pneumococcus immunity?
- capsular type specific immunity
- lymphoreticular system –> main place where phagocytosis to take place in spleen
What is functional or anatomic asplenia a risk factor for?
- risk factor for overwhelming infection with encapsulated organisms since spleen is place where phagocytosis of bugs primarily occurs
What is most effect treatment for most pneumococcus infections?
- beta lactams
what is the mech of beta-lactam resistance in pneumococcus? what does this mean for use of beta-lactamase inhibitors?
- resistance by altering penicillin binding proteins [PBP]
- thus does not use betalactamases
- betalactamase inhibitors [clavulinic acid, sulbactam] will not help
What 4 beta lactams are primarily used to treat pneumococcus?
penicillins:
amoxicillin [oral]
ampicillin [IV]
for sicker patients use gen 3 cephalosporins:
cefotaxime
ceftriaxone
What can cetriaxone treat?
- gram + or gram -
- gets into CSF
- good activity against 3 most common causes of meningitis [s. pneumoiae, n. meningitidis, H influenzae]
What is drug of choice for listeria?
ampicillin
Is meningitis caused by listeria treatable by cephalosporins?
No – you have to use ampicillin
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
Is ceftriaxone IV/IM or oral?
IV/IM only
How long is ceftriaxone half life? how frequent dosing?
- long half life
- once daily dosing
Does ceftriaxone penetrate blood-brain barrier?
yes
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
What are possible side effects of ceftriazone?
- allergy [rash –> anaphylaxis]
- some cross-rxn with penicillin
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
What are the three fluoroquinolones?
- ciprofloxacin
- levofloxacin
- mocifloxacin
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]
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]
What is the preferred fluoroquinolone for respiratory infection?
levofloxacin
Will ciprofloxacin treat respiratory infections?
not good choice because no reliable activity against gram + organisms
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
What are side effects of fluoroquinolones?
- GI intolerance
- dizziness/headache
- tenodonitis and tendone rupture
- GTc interval prolongation
Are fluoroquinolones okay for kids?
- not used in kids unless other alternative not available
What is the empiric treatment of bacterial meningitis? why?
- vancomycin and ceftriaxone
- use both in case it is resistant to beta-lactams
What does vancomycin act against? oral or IV?
IV only
active only against gram pos
What is empiric treatment of otitis media and sinusitis?
oral amoxicillin
main organism is s. pneumoniae
What is empiric treatment for pneumonia?
- amoxocillin [oral]
- azithromycin [oral]
- ceftriaxone [IV] (+/- azithromycin)
- levofloxacin [IV or oral]
What is pneumovax?
- vaccine against 23 serotypes of pneumococcus
- not immunogenic in children under 2 because T cell dependent
- made of purified capsule antigens
What is PCV13 [Prevnar-13]?
- vaccine against capsular polysaccharide from 13 serotypes
- made of capsular polysaccharides conjugated to mutant diphtheria toxoid
How can you prevent pneumococcus besides vaccines?
- chemoprophylaxis with penicillin
