L13: Bacterial Pneumonias II Flashcards
Mycoplasma pneumoniae morphology
Smallest
Lack cell walls→ stain poorly, pleomorphic shape
Plasma membranes contain sterols→ fusing to host cell membrane→ disguise
Mycoplasma pneumoniae can cause
atypical CAP
Also causes otitis, rhinitis, pharyngitis, tracheobronchitis (chest cold)
Atypical CAP caused by mycoplasma pneumoniae presentation
Non-productive cough 1-2 months, crackles, HA, chest pain, fever (except in <5 years)
is mycoplasma pneumoniae immunity long term?
no
mycoplasma pneumonia releases
hydrogen peroxide→ damage
Prevents clearance of airway→ colonization
lack cell walls, has sterols
Mycoplasma pneumoniae
fried egg appearance on culture
Mycoplasma pneumoniae
Mycoplasma pneumoniae CXR
patchy infiltrates
cold agglutinin assay
used to detect Mycoplasma pneumoniae by IgM antibodies that bind to the I antigen on the surface of RBCs at 4 C
mycoplasma pneumniae reservoir
HUMANS ONLY
person-to-person by respiratory droplets
chlmaydophila pneumoniae morphology
Tiny, non-motic coccoid, G-
Obligate intracellular parasites
2 forms of chlamydophila pneumoniae
Elementary body: infectious, endocytosed by cell→ Reticulate body: intracellular, replicates, becomes elementary body for release and reinfection
chlamydophila pneumoniae virulence factors
2 exotoxins
chlamydophila pneumoniae causes
Atypical CAP
+/- asymptomatic, mild sx
Non-productive cough, malaise for weeks/months
who gets chlamydophila pneumoniae
> 60 years
chlamydophila pneumoniae causes damage by
Replication→ Direct tissue destructionand inflammatory response
how to culture chlamydophilia pneumoniae
it’s difficult
immunity to chlamydophilia pneumoniae
Inflammatory response by neutrophils→ short term immunity
what to look for on microscopy of chlamydophilia pneumoniae
inclusions (RBs)
how else to detect chlamydophilia pneumoniae
serology
PCR
inclusions on microscopy
chlamydophilia pneumoniae
reservoir for chlamydophilia pneumoniae
person-to-person via respiratory droplets
Legionaella pneumphila morphology
Most are serogroup 1
Thin, pleomorphic, G- bacillus
Fimbriae, single, polar flagellum
Beta lactamase producer
Legionaella pneumphila reservoir
in nature, survive in protozoans
nature and moist environments
Aerosol transmission
NO person-to-person transmission
risk of legionella
Large inoculum
Compromised pulmonary or immune function:
Smoking, CHF, Chronic lung disease, elderly, alcoholics, immunosuppression
immunity of legionella
long lasting
legionella MOA
Inhalation of aerosols→ opsonized with C3b→ phagocytosis by macrophages→ facultative intracellular parasite: inhibit phagolysosome fusion→ replication inside phagosome→ phagolysosome lyses→ release chemotactic factors→ host cell dies, bacteria released
intracellular facultative macrophage parasite
chemotactic factors
legionella
Pontiac fever
Caused by legionella
self-limited, 2-5 days, resolves spontaneously: fever, chills, malaise, myalgia, HA, no pneumonia
Legionnaire’s disease
severe, acute atypical CAP with high mortality rate. 2-10 day incubation→ abrupt onset of fever, chills, dry cough, HA, GI and neuro sx, death due to shock or respiratory failure
how acute fibropurulent necrotizing pneumonia occurs in Legionnaire’s disease
Release of chemotactic factors→ influx of monocytes and PMNs→ increased serum proteins, deposition of fibrin in alveoli, release of enzymes and cytokines
gold standard for legionella diagnsoss
Culture on buffered charcoal yeast extract (BCYE) medium
rapid test for antigen production of legionella
URINE
EIA: highly sensitive but only serotype 1
Pseudomonas aeruginosa morphology
G- aerobic motile bacillus w/single flagellum
who does pseudomonas infect
Not extremely virulent→ requires compromised host
Opportunistic
pseudomonas can cause
UTI
pneumonia following respiratory therapy
Contaminated hot tubs→ skin, ear infection
Contaminated contact lenses→ eye infection
2nd leading cause of infection in burn patients
Common cause of death in cystic fibrosis
where is pseudomonas found/how it’s transmitted
Widespread in environment
Used for bioremediation
Carriage on skin and in feces, transmission via fomites, plants, fruits, hands
Opportunistic
Diagnosis of pseudomonas without tools
blue-green tinged sputum
patient may fluoresce
“fruity-smell”
how to culture pseudomonas
BAP or MacConkey media
Pyoverdin
green fluorescence:
Pyocyanin
blue “pus” virulence factor
catalyzes ROS production→ tissue damage
blue green color of pseudomonas is
water soluble
fluorescent
Elastases of pseudomonas
LasA, LasB
Work synergistically
Exotoxin A
Pseudomonas
A-B exotoxin (diphtheria, EF-2) → ciliastasis in the trachea, immunosuppression
Alginate
Pseudomonas
mucoid polysaccharide/slime layer
Adherence, inhibits mucociliary escalator (cystic fibrosis), antiphagocytic glycocalyx: inhibits complement, antibodies
Other pseudomonas virulence factors
Pili for attachment in clinical isolates
LPS endotoxin: shock, pyrogenic, DIC, necrosis
