SFP: respiratory infections Flashcards
Describe bacteria seen in bacterial pneumonias
Lots of pyogenic bacteria (neutrophils present, not lymphocytes), potentially mycobacteria (TB), sometimes actinomyces but unusual
Why do lung infections cause a large proportion of death?
The large alveolar surface area is exposed to contaminated air, we can aspirate nasopharyngeal flora, and the lungs are often involved in multisystem and systemic issues causing vulnerability
What are physical defenses to infection?
Cilia/mucus, surfactant, and cough reflex
What are immunological or humoral defenses to infection?
IgA/G/M, cytokines IL1 and TNF, and complement or fibronectin
What are cell mediated defenses to infection?
Neutrophils, eosinophils, macrophages, and lymphocytes
Neutrophils indicate ___ infection, while lymphocytes indicate ___ infection.
Bacterial, viral
Describe lobar pneumonia.
Impacts only one lobe of the lung and can be seen on CXR
Describe bronchopneumonia.
Patchy pattern seen throughout the lung, seen on CXR
What does ‘ground glass’ infiltrate tend to indicate?
Bronchopneumonia
What are the different etiological classifications of pneumonia?
- Community acquired
- Nosocomial (hospital acquired)
- Aspiration pneumonia (aspiration of gastric contents resulting in bacterial and chemical pneumonia)
What type of pneumonia is community acquired?
Bacterial
What type of pneumonia is community acquired atypical pneumonia?
Usually viral but may be bacterial
What type of pneumonia is nosocomial pneumonia?
Bacterial
What type of pneumonia is aspiration pneumonia?
Chemical and bacterial
What is necrotizing pneumonia?
A pneumonia in which bacteria collect and lung abscesses form; the tissue is damaged
What is the most common cause of bacterial pneumonia?
Strep pneumonia
What is the clinical presentation of bacterial pneumonia?
High fever, chills, productive cough, pleuritic chest pain
How do we diagnose bacterial pneumonia?
Blood culture
What is organizing pneumonia?
The infiltrate can organize, and fibrin can develop into fibrosis in the alveolar spaces
What are some complications of bacterial pneumonias?
Abscess, empyema (pus in pleural space), organization and fibrosis, bacteremia, pleuritis, pleural effusion
Describe lung abscess.
They often evolve from necrotizing pneumonia and are a localized suppurative process that involves necrosis of lung tissue. They vary, almost always rupture into airways, and may have a fibrous wall in chronic cases
What are the common organisms associated with lung abscess?
Staph aureus/MRSA, gram-negatives (pseudomonas), mixed infection
Why can abscesses be harder to treat than infection in alveolar spaces?
They tend to wall themselves off and do not allow the antibiotic into the abscess, while the alveolar spaces are highly vascularized and allow antibiotic in
Describe the clinical presentation of lung abscess.
Cough, fever, weight loss, chest pain; the course is variable and most resolve with antibiotic, but 10% die from sepsis.
What are complications of lung abscess?
Empyema, pneumothorax, hemorrhage, brain abscess
What is empyema?
Prurulent debris in the pleural space
Describe who gets aspiration pneumonia.
Often seen in debilitated patients, including those who are unconscious or have abnormal swallowing/gag reflex.
What are complications of aspiration pneumonia?
Lung damage with edema and bleeding, necrotization, lung abscess
Describe nosocomial pneumonia.
Acquired during hospitalization and seen in seriously ill patients
Who is particularly vulnerable to nosocomial pneumonia?
Those on ventilators
What are some common nosocomial pneumonias?
Gram negative rods such as klebsiella, pseudomonas, staph aureus (MRSA), Enterobacter, E. coli
What is the most common cause of community acquired pneumonia?
Strep pneumoniae
Which infectious agent is associated with acquiring pneumonia in groups through airway systems like air conditioning?
Legionella pneumophila
What is a special way to diagnose legionella pneumophila?
Fluorescent antibody technique using urine
Describe staph aureus as a cause of pneumonia.
Cause of secondary bacterial pneumonia and nosocomial pneumonia; has a high incidence of complications such as empyema and abscess. It is also seen in pneumonia associated with infective endocarditis in IV drug users
Describe klebsiella pneumoniae as a cause of pneumonia.
Big cause of gram-negative bacterial pneumonia. It impacts debilitated patients and is associated with thick sputum that may be difficult to cough up
What infectious agent is highly associated with pneumonia in a patient with poorly controlled diabetes?
Klebsiella pneumoniae
Describe pseudomonas aeruginosa as a cause of pneumonia.
Most common in nosocomial setting, and commonly seen in patient with burns, on respirators, or chemo. Can invade blood vessels and disseminate
What infectious agent is highly associated with pneumonia in cystic fibrosis patients?
Pseudomonas aeruginosa
Consolidation is seen in… (bacterial vs viral)
Bacterial pneumonia due to the presence of neutrophils
What is nocardia?
A rare pneumonia that occurs in the immunocompromised. Has poorly formed granulomas, necrotizing acute bronchopneumonia with abscess, and filamentous branching organisms
What can be identified by modified acid fast stains?
Nocardia
What is actinomyces?
Occurs in immunologically intact patients with emphysema and bronchiectasis. It leads to extensive tissue destruction and fistula formation. They have thin filamentous rods with terminal clubbing
Which pneumonia agent is associated with sulfur granules?
Actinomyces
Describe viral pneumonias.
They’re atypical, meaning a lack of consolidation or sputum production. We see interstitial pneumonitis and patchy inflammatory changes in the lung
What is the morphology of viral pneumonia?
Interstitial pneumonitis
Describe the clinical course of viral pneumonia.
Variable but usually mild and resolves. It can predispose patients to bacterial infection or cause respiratory distress but often is treated empirically
What is the pathogenic mechanism of viral pneumonia?
Attachment of organisms to the respiratory epithelium leading to necrosis of cells and an inflammatory response. There will be interstitial inflammation if it extends to alveoli
What is the typical histopathology of viral pneumonia?
Interstitial pneumonia with mononuclear infiltrate, and diffuse alveolar damage can occur
When are hyaline membranes seen?
With diffuse alveolar damage in viral pneumonia
What is cytomegalovirus (CMV)?
Produces huge cells with huge nuclei, and may produce severe pneumonia. Usually, it is just scattered cells without making the host sick, but can impact GI or retina
What is herpes simplex viral pneumonia?
Usually accompanied by extensive necrosis. May have intranuclear inclusions or ground glass nucleus
Where are atypical mycobacteria usually seen?
Immunocompromised patients
What is the most common atypical mycobacteria?
Mycobacterium avium intracellulare
What is a typical presentation of atypical mycobacteria?
Poorly formed granulomas or histiocytic inflammation
Describe M. bovis.
Found in unpasteurized milk and can cause GI and oropharyngeal infections
Acid-fast stains are often used for…
Mycobacteria
Describe aspergillus in terms of fungal pneumonia.
Usually found in patients with chronic disease or immunocompromised patients. Can be invasive and allergic and can cause hemorrhagic infarction with sparse inflammatory infiltrate. Can invade vessels and alveolar septa. Makes fungus balls
What is a characteristic of aspergillus?
45-degree branches and highly organized hyphae
What do we use silver stain for?
Fungus
What is mucormycosis?
A fungal pneumonia usually found in those with chronic disease. The fungus has 90 degree branching points and hyphae look scattered. It likes to invade blood vessels
Describe candida in terms of fungal pneumonia.
Usually in the immunocompromised and can have aspiration or hematogenous spread. They have pseudohyphae and budding yeasts.
Describe histoplasma in terms of pneumonia.
A granulomatous pneumonia that causes necrotizing granulomas that are calcified and surrounded by scar tissue. Common in Ohio river valley
Describe coccidiomycosis in terms of pneumonia.
Endemic in southwestern US; endospores and necrotizing granulomas with eosinophilic infiltrate
Describe cryptococcus in terms of pneumonia.
Granulomatous pneumonia with intracellular collection in histiocytes that looks bubbly. Found in pigeon droppings and mucicarmine stains capsule bright red
Describe pneumocystis jirovecii in terms of pneumonia.
Causes interstitial pneumonitis with basophilic alveolar exudate. It is confined to the lungs and may transform to cyst form. They cyst may rupture to release new trophozoites that attach to alveolar lining cells
What is the clinical presentation of someone with pneumocystis?
Variable; symptoms may be minimal but there may be fever, dyspnea, or dry cough that progresses to respiratory distress
How do we diagnose pneumocystis?
Bronchoalveolar lavage, tracheobronchial biopsy, immunofluorescent antibody kits, PCR assay
Describe blastomycosis in terms of pneumonia.
Associated with broad based budding and causes granulomas with central neutrophilic necrosis
