M-Community Acquired Pneumonia Flashcards
Pneumonia is the _____ most common cause of death in the US.
_________ adults in the US per year die.
I
8th, 4 million
What are the 4 main routes of infection for community acquired pneumonia?
What are the organisms for each route?
- microaspiration
- s. pneumoniae
- h. influenzae - macroaspiration
- normal flora
- anaerobes - inhalation
- mycobacterium
- mycoplasma
- chlamydia
- RSV
- Influenza
- legionella - hematogenous spread
- s. aureus
- s. typhi
What are the 3 major innate immunity defenses the body uses against pneumonia?
What are the 2 major acquired immunity defenses?
Innate
- cough reflex
- mucus production and ciliary elevator
- neutrophils
Acquired
- Cell-mediated immunity
- antibodies
What are the main diseases and drugs known to decrease the bodies defenses against pneumonia?
- altered mental status
- viral illness
- HIV/AIDs
- corticosteroids
- Tobacco
- diabetes
- drugs
- hypogammaglobinemia
- multiple myeloma
What cells line the respiratory tract?
What defenses are presented by these cells?
The respiratory tract is lined by:
- columnar epithelial cells with cilia
- stem cells
- mucous cells
This creates a mucus later that traps particulate matter and the cilia beats the foreign object/bacteria/whatever upward, out of the respiratory tract and then we swallow it into GI
What is the most common mode of acquisition for pneumonia by the following pathogens:
- S. pneumo
- mycoplasma pneumo
- H. influenzae
- Chlamydia pneumonia
- moraxella catarrhalis
- Legionella
- S. aureus
- G- bacilli
- viral (RSV, Influenza, metapneumovirus)
- GI content (aspiration)
- MTb, PCP
- microaspiration
- inhalation
- microaspiration
- inhalation
- inhalation
- inhalation
- hematogenous spread
- massive aspiration
- inhalation
- massive aspiration
- inhalation
What is the most common cause of pneumonia:
- under 5
- 5-45 yrs
- over 45
- bacterial/viral
- mycoplasma/chlamydia
- bacterial
Describe the history and physical of someone with pneumococcal pneumonia.
previously well individual who RAPIDLY develops:
- fever, chills
- pleurisy
- purulent sputum
Physical exam:
- tachycardic- acutely ill
- chest exam shows consolidation
- pleural friction rub
What would the CXR, labs, and sputum gram stain show for someone with pneumococcal pneumonia?
CXR- lobar consolidations, air bronchograms
Labs- leukocytosis, hypoxemia
Sputum G stain : PMNs and G+ diplococci, G+ cocci in chains and pairs
Describe the gram staining, hemolysis pattern, catalase, and sensitivities of S. pneumoniae.
How many serotypes are there?
G+ cocci in pairs or chains
Alpha-hemolytic
Catalase negative
Sensitive to:
Optichin and bile lysis
91 serotypes
For CAP, what is the prevalence of pneumonia caused by S. pneumoniae? How does this compare to other causes of CAP?
S. pneumoniae has a prevalence of 20-60% which is the greatest of any causes of CAP.
[viruses are 2-15, H. flue and G- are 3-10]
What are the 5 common clinical presentations associated with S. pneumoniae infections?
- Respiratory tract (upper- sinisitis, otitis media, lower- bronchitis, pneumonia, pleural effusion, empyema, bacteremia)
- Endocarditis
- Meningitis
- Arthritis
- Spontaneous bacterial peritonitis
What are the 2 upper respiratory tract infections associated with S. pneumonia?
- sinusitis
2. otitis media
What are the lower airway infections associated with S. pneumoniae?
- bronchitis
2. pneumonia (pericarditis, pleural effusion, empyema, bacteremia)
S. pneumonia colonizes ___ to ____% of adults and ______% of children in the nasopharynx.
Rates of ____% are detectable in the first year of life and ______with age.
5-10% of adults and 40% of children.
In the first year of life 70% are colonized but the rate decreases with age.
When do most s. pneumonia infections occur during the year?
How do most patients that get colonized present?
What does the infection usually follow?
Most infections occur in the winter and spring.
Most patients that are colonized are asymptomatic
The infection usually follows a viral URI
What are the major risk factors for getting a S. pneumoniae infection? (8)
- Younger than 2 or older than 65
- asplenia
- alcoholism
- diabetes
- antecedent influenza *****
- HIV
- new virulent strain of s. pneumonia
- defective humoral immunity
What are the 5 major virulence factors of s. pneumoniae? Which is the “major virulence determinant”?
- Polysaccharide capsule (major virulence determinant)
- pneumolysin
- PspA (pneumococcal surface protein A)
- PsaA (pneumococcal surface antigen A)
- IgA protease
What is the major virulence determinant of s. pneumoniae?
How many types are there?
Polysaccharide capsule- 91 types
There are smooth and rough strains of s. pneumoniae.
Which has a capsule?
Which is more virulent?
What are the functions of each?
Smooth- capsule, increased virulence, decreases phagocytosis in tissue and bloodstream invasions
Rough- no capsule- decreased virulence but promotes adherence to epithelium in respiratory tract
Spontaneous variation can occur between the 2 forms!
What does the highly negative charge of the s. pneumoniae capsule allow it to inhibit?
- interactions between CR3 and iC3b (neutrophil adhesive molecules)
- interactions with Fcgamma receptors and Fc portion of IgG to prevent phagocytosis
What are the 4 functions of the s. pneumoniae virulence factor, pneumolysin?
- pore forming cytotoxin released by autolysis that is lytic to the host cell.
- inhibits ciliary action of epithelial cells
- impairs respiratory burst of phagocytes
- induces inflammatory cytokines
What are the 2 functions of pneumococcal surface protein A?
Why is this surface protein relevant?
PspA:
- blocks binding of C3b to factor B
- binds to epithelial membranes
There are anti-PspA antibodies that are protective in animal models for infection
What are the 3 functions of pneumococcal surface antigen A?
- mediates metal ion uptake
- protects against oxidative stress
- binds GlcNac-B-1,3 Gal on respiratory epithelial cells
Basically, the four steps of pathogenesis of s. pneumoniae are colonization, evasion of mechanical barriers, evasion of immune mechanisms, and invasion.
How is the pathogen able to evade mechanical barriers?
- Aspiration below the larynx-
- chance increases with decreased conciousness (opiates, alcohol, barbiturates, benzodiazepine)
- chance increases with neurological disease (absence of gag reflex) - lack of mucociliary clearance
- smoking, COPD, bronchiectasis
What are the host defenses against s. pneumonia colonization?
IgA directed against capsular antigens
What are the host defenses against s. pneumoniae in the lungs? (3 things)`
- Alveolar macrophages (IgG, C3b for opsonization)
- PMN recruitment (IL8, TNFa)
- Th1 cytokines (IL12, TNF, IFNg)
What are the 3 main host defenses against s. pneumoniae in the blood?
- IgG2, C3
- C-reactive proteins
- splenic clearance
Starting with microaspiration, how does the progression of pneumonia with s. pneumonia occur?
- aspiration from nasopharynx
- failure of tracheobronchial clearance (mucus/cilia)
- intra-alveolar spread via pore of Kohn in small airways
- Congestion
- Red Hepatization
- Grey hepatization
- resolution
How does the lung appear during:
- congestion
- red hepatization
- grey hepatization
- edema and bacteria in alveoli
- PMNs, RBCs and fibrin in alveoli
- degeneration of cellular infiltrates and reabsorption
A patient comes to you saying that they felt fine and then all of a sudden, they had chills, fever (>38.5) and felt crappy.
They have been coughing up rust-colored sputum. They are having pleuritic chest pain, exacerbated by movement.
There is also referred abdominal pain.
What is the likely cause?
pneumococcal pneumonia due to:
- rapid onset
- rust sputum
- pleurisy
- ab pain (lower lobe infiltrate)
In someone with pneumococcal pneumonia, what do you notice on physical exam of the lungs?
- Toxic looking with tachycardia and fever
- Splinting on affected side
- Fremitus
- Auscultation - inspiratory crackles, E->A, pectoriloquy
- Pleural effusion- dullness to percussion, decreased breath sounds
What do you see on lab work for pneumococcal pneumonia?
CXR- lobar infiltrate, air bronchograms, (maybe pleural effusion)
WBC >15,000/mm3
Hypoxemia with VQ mismatch
What are the 4 major complications of pneumococcal pneumonia?
- Pleural effusion (uncomplicated, empyema 1%)
- Pericarditis
- Bacteremia- increased mortality, DIC, endocarditis, meningitis
- Meningitis