PATH: Pulmonary Infections Flashcards
What is pneumonia?
infection of the lung
What are the two classifications of acute, bacterial pneumonia?
Lobar- involving a whole lobe
Bronchopneumonia
How do almost all bacterial pneumonias start before becoming pneumonia?
MULTIFOCAL BRONCHITIS (may center around bronchi early on)
How common is lobar pneumonia?
very rare
Almost all acute bacterial pneumonias are due to what?
aspiration of saliva containing the pathogen
What is aspiration pneumonia?
pneumonia that is due to (large volume) aspiration of gastroesophageal contents or food misrouted from the oropharynx
What is a pulmonary infiltrate?
a radiologic manifestation of pneumonia or edema or hemorrhage (blood, pus or water).
What is consolidation?
manifestations of alveoli filled with blood, pus or water on physical examination or radiology, again not specific for pneumonia.
How do most types of pneumonia start?
acute inflammation (neutrophilic infiltration)
What occurs during the pathogenesis of pneumonia after acute phase inflammation? When?
subacute phase inflammation with macrophages replacing neutrophils (around day 3 of pneumonia)
What cell type is characteristic of subacute, bacterial pneumonia? What should you NOT get this confused with?
foamy macrophages
DO NOT confuse with “lipid pneumonia” due to lipid aspiration
What is alveolar necrotizing acute bacterial pneumonia commonly due to?
Staph aureus
Pseudomonas aeruginosa
Klebsiella
True or false: acute bacterial pneumonia is typically interstitial.
FALSE: is only interstitial if due to mycoplasma pneumonia
What is acute interstitial pneumonia commonly due to?
viruses
True or false: very few patients with acute bacterial pneumonia are hospatilized for it.
True: only 20%
What is alveolar non-necrotizing acute bacterial pneumonia commonly due to?
Streptococcus pneumoniae (pneumococcus), but can also be due to Legionella species, Mycoplasma species and many other bacterial species.
What is pneumococcal pneumonia?
lung parenchymal infection by Streptococcus pneumoniae (aerotolerant anaerobic Gram-positive diplococcus).
Who is most likely to get pneumococcal pneumonia?
Older men with COPD, who smoke, use alcohol, crack, etc.
What is the pathogenesis of pneumococcal pneumonia?
Normal flora that are acquired by aerosol inhalation that attach to respiratory epithelial cells via platelet activating factor receptor (that can be exposed by influenza neuraminidase), which binds to phosphorylcholine in the pneumococcal cell wall.
What potent cytotoxin is secreted by pneumococci? How does it work?
pneumolysin (binds to cholesterol in membranes and forms lethal pores in erythrocytes and leukocytes)
What is the prototype of pneumococcal pneumonia?
Pneumococcal lobar pneumonia
What are the 4 phases of pneumococcal lobar pneumonia?
(1) day 1: congestion with exudation of serous and frothy, blood-tinged fluid into alveoli
(2) days 2-3: red hepatization with drier, granular, dark red consolidation resembling liver
(3) days 4-7: grey hepatization with continuing consolidation, but color change to grey
(4) day 8 and following: slimy yellowish exudate, resolution without scarring
Describe the microscopic pathology of pneumococcal pneumonia.
acute non-necrotizing alveolitis, which stops at lobar septa because is non-necrotizing
What microscopic pathology lines up to phase 1 of pneumococcal lobar pneumonia?
Phase (1): engorged septal capillaries, with a few erythrocytes, edema fluid and bacteria in alveoli
What microscopic pathology lines up to phase 2 of pneumococcal lobar pneumonia?
Phase (2): continuing congestion, extravasation of red cells and numerous neutrophils and abundant fibrin in alveoli, infection spreading through pores of Kohn into adjacent alveoli
What microscopic pathology lines up to phase 3 of pneumococcal lobar pneumonia?
Phase (3): degenerating dead cells (neutrophils, erythrocytes, sloughed pneumocytes and bacteria) in the alveoli, fibrin nets extending through pores of Kohn, foamy macrophages replace neutrophils
What are the classic symptoms of pneumococcal pneumonia (in young people)?
Sudden single severe shaking chill (rigor), followed by sustained high fever and cough productive of blood-tinged “rusty” sputum +/- pleuritic chest pain.
What are the more common symptoms in heavy drinkers/smokers and older adults?
Increased sputum production and purulence with gradually progressive fever (over 2-3 days).
OR
Confusion, fatigue, and chilly, with no fever or cough.
What are the physical signs of pneumococcal pneumonia?
Low fever (102-103 F) Low tachycardia (HR 90-110/min) Mild tachypnea (RR 20-24/min) Pulmonary crackles Bronchial or tubular breath sounds Dullness to percussion
What do you COMMONLY see on a chest x-ray of pneumococcal pneumonia?
subsegmental alveolar infiltrates without air bronchograms
What value on a blood test gives a poor prognosis for pneumococcal pneumonia?
leukocytosis is a bad prognosis indicator
How do you treat pneumococcal pneumonia?
almost any beta-lactam antibiotic
What is staph aureus pneumonia?
lung parenchymal infection by Staphylococcus aureus
Where is staph aureus pneumonia commonly acquired?
28% of hostital-acquired pneumonias
True or false: lung parenchymal infection by Staphylococcus aureus pneumonia commonly follows viral respiratory infections.
True! (especially influenza)
List the virulence factors of staph aureus.
1) exotoxins (e.g. leukocidins, hemolysins)
2) Protein A
3) Resistance to many commonly used antibiotics in methicillin-resistant strains.
What is the role of Protein A (staph aureus virulence factor)?
binds to TNF receptor 1 and opens path for invasion between epithelial cells
Describe the gross pathology of staph aureus pneumonia.
Heavy plum-colored lungs, which exude bloody fluid on sectioning and develop numerous small abscesses, which enlarge (and in children can be thin-walled “pneumatoceles”).
What pathogenic features commonly accompany staph aureus pneumonia?
Commonly with pleuritis and empyema.
Describe the microscopic pathology of staph aureus pneumonia.
Acute necrotizing bronchitis, bronchiolitis and alveolitis, with abundant neutrophils, fibrin and edema fluid (that can condense into hyaline membranes). Commonly with hemorrhage and abscesses.
What does a chest x-ray of a patient with staph aureus pneumonia look like?
bronchopneumonic (alveolar) infiltrates +/- abscesses, pleural effusions
What is the treatment for staph aureus pneumonia
Oxacillin (or another beta-lactam) for methicillin-sensitive
Vancomycin (or linezolid) for methicillin-resistant.
Which is worse, staph aureus pneumonia or pneumococcal pneumonia? Why?
Staph aureus pneumonia (it is necrotizing and abscessing and has a 50% mortality rate)
What is legionella pneumonia?
Lung parenchyma infection by Legionella species (fastidious Gram-negative bacilli)
What is the habitat of legionella?
Warm water (25-42 degrees) in water heaters, shower heads, air conditioners, etc.
Can hide inside amoebae.
What is the pathogenesis of legionella pneumonia?
Once inhaled or aspirated, attaches to respiratory epithelial cells and macrophages by flagellae and pili. After phagocytosis, evade intracellular destruction by inhibiting phagosome-lysosome fusion
What two legionella genes are involved with inhibiting phagosome-lysosome fusion?
DOT (defective organelle trafficking)
ICM (intracellular multiplication)
True or false: legionella is transmitted from person to person?
FALSE! It is NEVER transmitted from person to person
Describe the gross pathology of legionella pneumonia.
bulging firm rubbery areas of consolidation
Describe the microscopic pathology of legionella pneumonia.
acute non-necrotizing alveolitis, with early infiltration by numerous macrophages (unusual in acute pneumonia)
What specific symptom suggests legionellla pneumonia?
GI symptoms (like diarrhea)
What specific signs suggest Legionella?
neurological signs (like confusion)
What does a chest x-ray of a patient with legionella pneumonia look like?
initially patchy unilobar bronchopneumonic (alveolar) infiltrate that progresses, + (in 50%) pleural effusion
What is the result of a gram stain for legionella?
usually a false negative
What type of culture agar does legionella require?
buffered charcoal yeast extract agar (ideally supplemented with antibiotics and dyes).