February 9, 2016 - Microbiology and Pathology Flashcards
Spread of Organisms to Alveoli
1) Aspiration of the oropharynx
2) Inhaled droplets or airborne particles
3) Hematogenous spread
4) Contiguous spread
Stages of Lobar Pneumonia
Congestion - Day 1/2
Rep Hepatization - Day 3/4 - Blood cells, neutrophils, and fibrin make their way into the pulmonary alveoli.
Grey Hepatization - Day 5-7 - The blood cells are broken down leaving a fibrinosuppurative exudate.
Recovery - Day 8-21
Red Hepatization
The second stage of lobar pneumonia. The lungs are filled with red cells.
Grey Hepatization
The third stage in lobar pneumonia when the red cells and infiltrate have been broken down, leaving a thick exudate.
Interstitial Pneumonia
Is a form of interstitial lung disease.
Infiltrates in the alveolar walls, but an absence of alveolar exudate.
Can cause scarring of the lungs.
Common Organisms of Community Acquired Pneumonia
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catharralis
Klebsiella pneumoniae
Common Organisms of Healthcare Acquired Pneumonia
Staphylococcus aureus (including MRSA)
Pseudomonas auruginosa
E. coli
Other Gram-negative bacteria
Typical vs. Atypical Pneumonia
Typical pneumonia is often caused by the typical pathogens and usually causes lobar pneumonia, has a more acute onset, and has a productive cough.
Atypical pneumonia is often caused by atypical pathogens and can cause interstitial pneumonia. It’s onset is usually more insidious and has a dry cough.
Streptococcus pneumoniae
Gram positive cocci (often in pairs or chains)
The most common cause of CAP
Encapsulated organism
Found in the nasopharynx
20-30% of patients will have bacteremia
Pneumococcal Vaccines
Targets antigens on the capsule of Strep. pneumo.
Different types. Recommend for patients over 65.
Common Organisms of Atypical Pneumonia
Chlamydophila pneumoniae
Mycoplasma pneumoniae
Legionella pneumophila
Usually have a less acute onset and an interstitial pattern.
Aspiration Pneumonia
Caused by aspiration.
Typically a mix of upper airway and oral flora. The big thing, is that anaerobes tend to be present and you need to account for them in your antibiotic selection.
“Other” Causes of Pneumonia
Francisella tularensis - Exposure to infected rodents, rabbits, or caribou
Bacillus anthracis - Exposure to infected animals / inhalation of spores
Coxiella burnetti - Exposure to infected sheep
Chlamydia psittaci - Bird exposures (often parakeets)
Hantavirus - Exposure to mouse droppings
Endemic fungi - Specific travel history
