Lower respiratory tract bacteria 2 Flashcards
(14 cards)
Describe the Two classes of Atypical pneumonia and the bacteria involved
Walking Pneumonia - Mycoplasma pneumoniae - Chlamydophila pneumnoiae Toxic Pneumonia - Legionella pneumophila
Describe the symptoms and treatment of atypical pneumonia
Symptoms:
- Bronchopneumonia with gradual onset
–> fever, headache, fatigue, muscle ache, dry cough, with SCANT/WATERY SPUTUM
Treatment:
- Tetracycline and erythromycin
–> empiric therapy for atypical pneumonia (absence of signs of pneumococcal pneumonia)
Describe the characteristics of Mycoplasma pneumoniae
- Smallest free living bacteria, pleomorphic
- NO PEPTIDOGLYCAN!!!
- Membrane contains sterol
- culture requires supplementation with sterols and nucleotide precursors
- fried egg colon morphology
- RESTRICTED TO HUMANS
- -> Low infectious dose transmission by respiratory droplets –> tracheobronchitis
describe the virulence factors of mycoplasma pneumoniae
P1 adhesion
- binds to base of cilia causing ciliostasis which results in epithelial cell damage/death and defective mucociliary clearance.
- -> loss of mucociliary clearance results in mucous/fluid accumulation in lungs which causes pneumonia.
Describe the diagnosis and treatment of mycoplasma pneumoniae
Diagnosis:
- microscopy/ culture NOT RECCOMENDED
- colg agglutinin test not very specific or sensitive, utility has been questioned
- PCR has high sensitivity, specificity improving
- Serology
Treatment: Tetracycline and macrolide (erythromycin)
- NOT BETA-LACTAMS –> no peptidoglycan thus no target
Describe Chlamydophila pneumoniae
- Small gram-negative, obligate intracellular pathogen
- cause Atypical pneumonia (walking pneumoniea
- Implicated in atherosclerotic plaque formation, asthma, MS and rheumatoid arthritis
Describe treatment/diagnosis of chlamydophila pneumoniae
Diagnosis:
- Microimmunofluorescence = test for anti-chlamydophila ab
- PCR detection
Treatement = tetracycline and macrolide (same as M. pneumoniae)
describe chlamydophila pneumoniae infection cycle
1) an elementary body (EB, infectious particle) attaches and enters the cytoplasm of the susceptible host cell.
2) The EB reorganizes to form a reticulate body (RB)
3) the RB then undergoes several binary fissions and reorganize back into EB’s
4) EB’s emerge from the inclusions and infect another host cell.
Describe legionella pneumophila
- Gram negative (inside of cells = coccobacilli and outside the cell = pleomorphic)
- difficult to culture due to slow growth, fastidious, high humidity
- Ubiquitious in freshwater lakes, streams, ground water, potting soil, mud, riverbanks
- mainly exist as parasites of amoeba (intracellular lifestyle)
- Transmission = aerosols from manmade water supplies that harbor legionella and their amoeba host
What are the two diseases that legionella pneumophila cause
Legionnaires disease (pneumonia) and Pontiac fever
describe the pathogenesis of legionella pneumophila
- Target and attach to alveolar macrophage using pili, flagella, numerous proteins
- enter macrophage in a endocytic vacuole (coiling phenomenon)
- Hijacks the cell and injects hundreds of bacterial proteins into cytosol using type 4 secretion systems
- -> prevents fusion with lysosome, recruits ribosome, mitochondria, ER to the vacuole (now called legionella-containing vacuole (LCV))
- -> replication of bacteria and eventually leads to the lysis of the host cell and the process starts over again.
describe the clinical manifestation of legionella pneumophila
- Severe toxic pneumonia develops
- myalgia, headache, rapidly rising fever,
- dry cough, may become productive
- chills, pleurisy, vomiting, diarrhea, confusion, delirium
- patchy infilitrates on Chest X-ray
- ELEVATED WBC count
- patient becomes progressivel ill over 3-6 days and results in shock, respiratory failure or both
how to diagnose legionella pneumophila
- Culture
- Direct fluorescent antibody detection of organism (only positive in 50% of patients)
- Nucleic acid amplification test (possibility for false positives
Describe treatment legionella pneumophila
Treatment:
- NOT BETA-LACTAMS (most isolates produce beta-lactamases
- Currently a macrolide or a fluoroquinolone is preferred
PREVENTION:
minimizing exposure to/production of contaminated aerosols
