B3.014 Pulmonary Pathogens Flashcards
who is susceptible to opportunistic pneumonia?
immunocompromised patients
what types of pneumonia are typically caused by bacteria?
CAP and HAP
what are the primary bacteria that cause pneumonia?
streptococcus pneumoniae
mycoplasma pneumoniae
legionella pneumophila
what types of pneumonia are typically caused by viruses?
opportunistic (pediatric/geriatric)
what are the primary viral causes of pneumonia?
flu a and b, parainfluenza virus, respiratory syncytial virus (RSV)
what type of pneumonia are typically caused by fungi?
opportunistic (immunosuppressed, AIDS, cancer therapy, transplants)
hemolytic properties of s. pneumoniae
alpha hemolytic
what type of capsule surrounds s. pneu?
carbohydrate
>90 sertoypes
what does it mean to be naturally competent for DNA transformation?
has the ability to mutate by taking up DNA from plasmids to make itself more pathogenic
discuss the classification of streptococci
gram + chains normal flora of skin and mouth catalase negative may produce exotoxins
what types of strep are B hemolytic?
group A strep (GAS) : s. pyrogenes
group B strep (GBS) : s. agalactiae
what types of strep are alpha hemolytic?
viridans (green) strep: s. mutans
s. pneumoniae
what types of strep are gamma hemolytic?
enterococcus (GDS)
who hosts s.p.?
humans
where is asymptomatic carriage of s.p. common?
nasopharyngeal mucosa
5-75% of population
considered a commensal
how does transmission of s.p.?
respiratory droplets
how do most cases of s.p. arise?
spread of endogenous organisms
our own natural flora gets into the wrong niches
other than pneumonia, what common illnesses develop as a result of s.p.?
sinusitis, otitis media, meningitis
what are predisposing factors for getting s.p?
respiratory viral infections
what is pneumonia?
aspiration of bacteria and replication in alveolar spaces
how long is the incubation period of pneumonia?
1-30 days
what are symptoms of pneumonia?
abrupt onset of fever and shaking chills
pleurisy, productive cough, blood tinged sputum
risk factors for pneumonia
antecedent viral infection of resp tract, especially influenza
smoking
age <2 or >65
hematological disorders, asplenia, chronic pulmonary disease, diabetes, renal
how can you differentiate typical vs atypical pneumonia?
based on symptoms atypical "walking" pneumonia: -slow onset -moderate fever -non-productive cough -headache
key atypical pneumonia pathogens
chlamydia pneumoniae legionella pneumonia mycoplasma pneumonia chlamydia psittaci coxiella burnetii some viruses
describe meningitis
100% mortality without antibiotic treatment
25% with treatment
inflammation frequently leads to permanent brain damage, blindness, hearing loss, learning disabilities
describe otitis media and sinusitis caused by s.p.
50% of middle ear infections
sinusitis occurs in all age groups
can develop into megingitis
virulence factors of s.p.
polysaccharide capsule
C polysaccharide
describe the s.p. polysaccharide capsule
90 serotypes
essential for pathogenesis
anti phagocyctic
immunogenic
describe the s.p. C polysaccharide
complex of phosphorylcholine, peptidoglycan and teichoic acid
common to all serotypes
present in urine and serum during infection
what toxins are associated with s.p.
pneumolysin
autolysin
IgA protease
describe pneumolysin
cholesterol dependent pore forming toxin
toxic to bronchial epithelial cells
activates classical complement pathway
describe autolysin
binds to cell wall
degrades peptidoglycan, resulting in bacterial cell lysis
releases pneumolysin from cell
releases cell wall components that activate the inflamm response
antibodies to autolysin can be protective
describe IgA protease
blunts mucosal adaptive immune response
what are other characteristics of s.p. culture other than hemolysis/shape/catalase neg
bile solube
optochin-sensitive
Quellung (swelling) reaction: shows capsule on bacteria
where can C polysaccharide be found?
urine and serum
how is capsular antigen detected?
latex agglutination assap
what MIC values are considered susceptible?
<2 ug/ml
what MIC values are considered resistant?
> 8 ug/ml