L13: Bacterial Pneumonias II Flashcards by Jeri Sheldon (AZ PA Mast 20)

Mycoplasma pneumoniae morphology

Smallest
Lack cell walls→ stain poorly, pleomorphic shape
Plasma membranes contain sterols→ fusing to host cell membrane→ disguise

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Mycoplasma pneumoniae can cause

atypical CAP

Also causes otitis, rhinitis, pharyngitis, tracheobronchitis (chest cold)

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Atypical CAP caused by mycoplasma pneumoniae presentation

Non-productive cough 1-2 months, crackles, HA, chest pain, fever (except in <5 years)

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is mycoplasma pneumoniae immunity long term?

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mycoplasma pneumonia releases

hydrogen peroxide→ damage

Prevents clearance of airway→ colonization

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lack cell walls, has sterols

Mycoplasma pneumoniae

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fried egg appearance on culture

Mycoplasma pneumoniae

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Mycoplasma pneumoniae CXR

patchy infiltrates

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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

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mycoplasma pneumniae reservoir

HUMANS ONLY

person-to-person by respiratory droplets

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chlmaydophila pneumoniae morphology

Tiny, non-motic coccoid, G-

Obligate intracellular parasites

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2 forms of chlamydophila pneumoniae

Elementary body: infectious, endocytosed by cell→ Reticulate body: intracellular, replicates, becomes elementary body for release and reinfection

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chlamydophila pneumoniae virulence factors

2 exotoxins

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chlamydophila pneumoniae causes

Atypical CAP
+/- asymptomatic, mild sx
Non-productive cough, malaise for weeks/months

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who gets chlamydophila pneumoniae

> 60 years

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chlamydophila pneumoniae causes damage by

Replication→ Direct tissue destructionand inflammatory response

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how to culture chlamydophilia pneumoniae

it’s difficult

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immunity to chlamydophilia pneumoniae

Inflammatory response by neutrophils→ short term immunity

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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