Flashcards in P- Pulmonary Infections Deck (79):
Pneumonia (infection of the lung parenchyma) can occur when host defenses are breached. What are the 6 most common causes of this?
1. loss of cough reflex
2. injury to mucociliary apparatus
3. alveolar macrophage dysfunction
4. immune defects
5. immunosuppressive therapy
What are 4 situations that could cause the loss or suppression of cough reflex?
3. neuromuscular disorder
4. drugs --> aspiration or gastric contents
What are 4 things that can injure the mucociliary apparatus leading to pneumonia?
2. hot/corrosive gas
3. viral infections
4. Kartagener's (ciliary impairment)
What are 4 causes of alveolar macrophage dysfunction?
3. anoxia (complete of oxygen)
4. oxygen intoxication
Defects in innate or humoral immunity lead to infections by ___________ while defects in cell-mediated immunity lead to infections with ___________________ like ______ and _______ or low virulence organisms like _________________.
Humoral = pyogenic bacteria
1. intracellular pathogens like herpesvirus or mycobacteria
2. low virulence like pneumocystis
What are the 3 most common infections that leukopenia predisposes a person to?
What are the 3 general ways pneumonias can be classified?
1. clinical setting - to guide initiation of empiric therapy
2. identity of the pathogen - directed therapy
3. lobar vs. bronchopneumonia
What is the cause of most cases of community acquired acute pneumonia?
(_______following a _________)
What is the typical clinical presentation?
bacterial infection following a viral URI
Rapid onset with high fever, chills, pleuritic chest pain, cough with purulent sputum, hemoptysis
What are the 4 major risk factors for CAAP?
1. Chronic disease: COPD, diabetes, CHF
3. extremes of age
4. asplenia/splenic dysfunction (sickle cell)
What are the five infectious agents associated with CAAP (community acquired acute pneumonia)?
When they are cultured, which do you perform susceptibility testing on before giving antibiotic?
1. Streptococcus pneumoniae- susceptibility testing
2. Haemophilus influenza
3. Moraxella catarrhalis
4. S. aureus- susceptibility (oxacillin and vancomycin)
5. Klebsiella pneumoniae
What would cause a sputum test submitted for pneumonia to be rejected by the microbiology lab?
If it is found to have oropharyngeal bacteria it will not be representative of lower respiratory tract contents and will be rejected.
How do you know that a sample is sputum and not "spit" (thus coming from the lower respiratory tract and not oropharyngeal)?
Sputum - neutrophils, mucus, very FEW squamous epithelial cells
You did a sputum gram stain and noticed lancet shaped G+ diplococci in the background of neutrophils. What is the suspected organisms?
What also needs to be present for this to be considered diagnostic?
What test is more specific but less sensitive that can be used to confirm?
S. pneumonia is likely, but pneumococci can also be found in normal oropharyngeal flora, so the gram stain and culture must have:
1. CONSIDERABLE amounts of the organism
2, virtual absence of other flora
Positive blood culture is more specific but less sensitive so it will often come up negative
What are the 4 major infections causes by S. pneumoniae?
2. otitis media
How is S. pneumonia treated?
How can it potentially be prevented?
It is treated with quinolones and/or beta lactams.
there is a vaccine but it is available for high risk groups (elderly, immunocompromised, splenectomized individuals)
Describe the gram staining capabilities of H. influenza.
What are the requirements for culturing it?
What are the 2 major subgroups of H. flu?
Which used to cause meningitis, septicemia, septic arthritis and epiglottitis? Why doesn't it anymore?
H influenza is a small gram negative rod that is normally found in the oropharyngeal flora
To culture it, you must use chocolate agar.
1. Encapsulated (a-f)- type B caused meningitis, arthritis, septicemia, epiglottitis. A vaccine was developed in the 80s so it is less prevelant
2. Unencapsulated - most diseases today
What is the most common bacterial cause of acute exacerbations of COPD?
This bacteria has also been implicated in CF, otitis media, epiglottitis and sinusitis.
H. influenza is the most common bacterial exacerbation of ________, but also causes infections in patients with __________.
However, most infections are ______, _______, and __________.
COPD, but also causes infection in cystic fibrosis patients.
2. otitis media
You take a sputum sample from someone with CAAP. You perform a gram stain and see G- diplococci.
What do you think the organism is?
What type of plates can it be cultured on?
What drug can NOT be used to treat it?
Moraxella catarrhalis - common exacerbation of COPD
Culture it on blood agar/chocolate agar
You cannot use ampicillin because all strains of M catarrhalis produce a beta lactamase
What organism is an important cause of secondary pneumonias in patients with antecedent viral infections like measles and influenza?
What do lung infections with s. aureus lead to?
What can these infections occur as a by-product of?
S. aureus lung infection can occur as a by-product of right sided endocarditis in IV drug users, or as a byproduct of nosocomial infection
Susceptibility testing for s. aureus are directed at what two drugs?
1. oxacillin resistance - MRSA, most beta lactams don't work
2. vancomycin-resistance - rare in the US
A chronic alcoholic comes into the hospital and is suspected of CAAP. You do a sputum gram stain and notice large gram negative rods with thick, mucoid polysaccharide capsules. What is the suspected organisms?
Klebsiella pneumoniae- affects malnourished/debilitated
What is the main virulence/pathogenic factor of klebsiella pneumonia?
thick mucoid polysaccharide capsule
Describe lobar pneumonia.
What are the 4 stages?
Fibrinosuppurative consolidation in a large portion of lobe or whole lobe.
2. red hepatization
3. grey hepatization
What is the gross appearance of congestion? What is the microscopic appearance?
Thick, red, boggy, heavy lung
Alveoli contain a few neutrophils, proteinaceous fluid, bacteria. Alveolar capillaries are congested with RBCs
What is the gross appearance of red hepatization? What is the microscopic appearance?
Looks like a liver
RBCs, neutrophils, fibrin fill the alveolar spaces
Describe the gross appearance of grey hepatization?
What is the microscopic appearance?
dry, grey, firm
RBCs lyse, intraalveolar exudate persists
What happens during resolution of lobar pneumonia after grey hepatization stage?
Alveolar exudate is digested making a fluid debris that is reabsorbed, ingested by macrophages, coughed up or swallowed.
How does the appearance of bronchopneumonia differ from lobar pneumonia?
Which is more likely to have pleural involvement?
Bronchopneumonia is more patchy and diffuse with the consolidation involving multiple lobes.
Usually bilateral and basal with an elevated, granular appearance.
Lobar pneumonia is more likely to involve the pleura
What are common complications of pneumonia if it doesn't resolve without residual damage?
2. abscess formation
3. organization with fibrosis
4. bacteremic spread via septic emboli
Describe the inflammatory changes and location found in atypical pneumonia.
"Walking pneumonia" has patchy inflammatory changes confined to the alveolar septae and pulmonary interstitium. There is little to no consolidation, only mildly elevated WBC count and no alveolar infiltrates.
What are the 5 major causes of atypical community acquired pneumonia?
1. Mycoplasma pneumoniae
3. Chlamydia pneumoniae
4. Legionella pneumophila
5. Coxiella burnetti (Q fever)
What is unique about the structure of mycoplasma pneumonia?
What is diagnosis based on?
What is treatment?
mycoplasma pneumonia lacks a cell wall.
Diagnosis is made on clinical criteria (young adults, insidious onset) but serology can be helpful.
Treatment is antibiotics but NOT beta- lactams or cephalosporins because it lacks a cell wall
What viruses can cause pneumonia?
How can they be diagnoses?
2. Human metapneumovirus
3. influenza A and B
4. adenovirus (conjunctivitis, sore throat in transplant/military)
5. parainfluenza virus
Diagnosed with direct fluorescent antibody (DFA) on nasopharyngeal secretions
What are the 2 obligate intracellular pathogens that cause atypical pneumonia?
How are they diagnoses?
1. Coxiella burnetti
2. chlamydia pneumoniae
Diagnosis is based on history and serology (cannot be cultured)
Atypical pneumonia has patchy involvement with mononuclear infiltrate consisting of ______, ______ and _______ confined to the ___________. The septae are ______ and _______ but free of exudate.
Nuclear infiltrate consisting of:
3. plasma cells
confined to the alveolar septae which is widened and edematous but free of exudate.
Atypical pneumonia caused by bacteria are usually treated with what? How are viral pneumonias treated?
Bacteria - fluoroquinolone or macrolide (azithromycin, ZPAC)
Viral pneumonia- resolves with time
Describe the organism of Legionella pneumophila.
What stain is used to visualize it?
What are the 2 potential diseases people get from it?
What is the distinguishing clinical feature that differentiates it from other causes of pneumonia?
Who is at greatest risk?
It is a small gram neg rod that does not stain with gram stain, but rather silver stain.
1. Legionnaire's disease- pneumonia
2. Pontiac fever- influenza-like without pneumonia
More likely to present with alveolar exudate, and diarrhea.
Transplant patients, underlying cardiac, renal, immunologic or hematologic conditions are at greatest risk.
What media is required to grow legionella?
buffered charcoal yeast extract agar
What test is necessary for diagnosis of legionella?
Urinary antigen test because most patients with legionella aren't making sputum.
What are the most common causes of nosocomial pneumonia?
Why are these organisms difficult to treat?
1. S. aureus
2. Gram neg rods - pseudomonas aureginosa, acinetobacter baumanii, enterics
They are difficult to treat because they tend to be multi-drug resistant
What is the criteria for diagnosing ventilator-associated pneumonia?
clinical and radiographic
Not necessarily based on culture results
Who is the patient likely to develop aspiration pneumonia?
What would the infection caused by macroaspiration look like?
1. debilitated patients (older,stroke, recumbent)
2. chronic alcoholics
Aspirate oropharyngeal and/or gastric contents
The infection is often necrotizing and can lead to abscess formation because it contains bacteria AND acidic stomach chemical.
What are the most common organisms (anaerobes and aerobes) involved in macroaspiration pneumonia?
1. S. aureus
2. S. pneumoniae
3. H. influenzae
What is a lung abscess?
What are the mechanisms by which organisms are introduced to cause abscess?
It is a localized, suppurative, necrotic process accompanied by cavitation
1. aspiration of oropharyngeal flora
2. antecendent bacterial pneumonia with CAAP and nosocomial infections
3. post-obstructive pneumonia in lung cancer patients
4. septic emboli from endocarditis
5. hematogenous spread from bacteremia/fungemia
Where would the abscess be if it was caused by aspiration?
A single right-sided abscess because the right sided bronchus is straighter
Describe the abscess that would form because of pneumonia or bronchectasis.
There would be multiple basal areas of abscess
Describe the abscess that would result from septic emboli.
There would be multiple bilateral abscesses in any region.
What are the two locations an abscess can rupture into? What does each cause?
1. rupture into the airway--> air/fluid level on imaging
2. pleural space--> empyema, bronchopleural fistula
In immunocompetent patients, chronic pneumonia presents most often as _________.
In the immunocompromised patients, chronic pneumonia can cause ______________.
The main agents are ____ and _______ agents,
localized, granulomatous, with or without regional lymphadenopathy
2. fungal infection
Describe the structure of mycobacteria.
How do they stain?
Mycobacteria are rods with waxy mycolic acid cell walls. Because of this they resist decolorization and do not gram stain.
They can be stained with AFB stain where they appear red.
Describe Primary TB.
How does the bacteria get to the lung?
What area of the lung is infected?
When does CMI start? How?
What factors are utilized to begin granuloma formation?
Bacteria in inhaled from close contact with an actively infected individual.
The organisms lodge in distal airspaces in the lower lobes or lower portion of the upper lobes.
They get ingested by macrophages but are not killed due to inhibition of acidification and ceasing of maturation of phagolysosomes.
After 3 weeks, CMI begins because the bacteremic spread has reached lymph nodes.
IL-12 from the macrophage induces IFNg production from TH1 which further activates macrophages which make TNFa, NO and chemokines (which attract monocytes -->histiocytes--> granulomas)
A caseating granuloma containing AFB present in the parenchyma is called ___________. If an associated draining lymph node also has AFB, it is called a _____________________.
Ghon focus = just parenchyma
Ghon complex = lung parenchyma and associated lymph node
What is seconday TB?
When does it typically arise?
What region of the lung is it localized to?
What does it cause?
Can follow primary TB, but usually arises from reactivation of dormant primary TB after years of latency.
It occurs when host resistance is weakened.
Localizes to the apex of the lung (more O2).
Foci are walled off and cavitation may occur.
How do you differentiate active lesions from fibrocalcific nodules of secondary TB?
Active lesions - coalescing caseating granulomas with AFB
Fibrocalcific lesions- no identifiable AFB
What is progressive TB?
If depends on the immune status of the host.
It can resemble acute bacterial pneumonia with lower/middle consolidation, hilar lymphadenopathy, pleural effusion.
Can lead to miliary TB or TB meningitis
What are the common places extrapulmonary miliary TB can spread?
2. bone marrow (pott's disease)
How are M. kansasii, MAC and M. abscessus spread?
Who is likely to be infected?
They are acquired from the environment and are NOT spread person-to-person.
Infect immunocompromised people OR
Immunocompetent with COPD, pneumoconiosis, CF
If a patient is suspected of having active TB, how many sputum samples should be submitted to Micro lab for AFB culture and smears?
What is the time frame for collection?
3 sputum samples should be collected over 24 hours with atleast one in the early morning (which usually has higher concentration of the organism)
If the patient is having trouble providing a sputum sample (ex. small child that is unable to differentiate spit from sputum), what should be done to get a specimen?
Bronchoscopy to collect "induced sputum"
Why can you not use a swab to get a culture for mycobacteria?
mycobacteria present in low numbers so a high volume specimen is required for testing.
The culturing of MTb is the gold standard for diagnosis of Tb. In addition to proving the presence of MTb, why is the culture important?
It is used for susceptibility testing to guide therapy.
(isoniazid, rifampin, pyrazinamide, ethambutol)
What are the 4 features endemic fungi have in common?
1. they have typical geographic distribution
2. Immunocompetent have isolated pulmonary involvement
3. immunocompromised have disseminated disease
4. fungi are dimorphic (moulds at 25 degrees in the soil and yeasts at 37 degrees in the body)
What three organism are the most common endemic fungi in the US?
1. histoplasma capsulatum
2. coccidioides immitis
3. blastomyces ermatitidis
Where would one find histoplasma capsulatum geographically?
What does it look like as a mould? Yeast?
Mississippi/Ohio, SE US
Mold : tuberculate macroconidia
Yeast: small budding yeast
Where would one find coccidioides immitis geographically?
What does it look like as a mold? Yeast?
It is found in SW and western US (RGV, Arizona, southern CA)
Mold- alternating barrel shaped arthroconidia
Yeast- spherules with endospores
Where would one find blastomyces dermatititidis?
What does it look like as a mold? Yeast?
It is found in SE US, Mississippi/Ohio River valleys
Mold: single round spores on cocidia (lollipops)
Yeast: thick walled, broad based budding yeasts
Coccidioides may have a ____________________ response where _________ form in response to spherules and ________ respond to released _____________.
Pyrogranulomatous response where granulomas form in resonse to spherules and neutrophils respond to released endospores
What is the initial response to blastomyces infection?
How is diagnosis of an endemic fungal infection made?
2. appropriate cultures
3. Urinary antigen test (histoplasma in HIV)
Need a sufficient volume of specimen- NO SWABS
Do NOT do UAT for immunocompetent people
What is the likely cause of pneumonia in a patient with CD4 count:
1. more than 200
2. less than 200
3. less than 50
1. bacteria, TB
3. CMV, MAC
What family of virus does CMV belong to?
What infection does it cause in immunocompetent people?
What does it cause in immunocompromised people?
How is diagnosis made?
Immunocompetent- asymptomatic or mono-like presentation
-Transplant patients get pneumonitis with systemic disease
- HIV patients get GI and CNS infection
CMV has an "owl eye" appearance on histology with eosinophilic/basophilic inclusions
DO biopsy, molecular testing
Who is likely to get infection by pneumocytis jiroveci (PCP)?
What is the characteristic appearance of the lungs?
What tests can be done?
Lungs have foamy pink staining intraalveolar exudate.
1. Silver stain hilights cysts
2. GW stain shows trophozoite stage
3. Brochoalveolar Lavage (BAL)
4. DFA (direct fluorescent Antibody)
Who does MAC affect?
How do they acquire this infection?
Do you see granulomas?
MAC is in water, soil and dust.
Immunocompromised people (CD4t have T cells, but there are macrophages full of AFB.
What kind of fungi (yeast, mold, dimorphic) is Aspergillus? Where is it found?
What diseases can it cause?
What happens if it colonizes an old TB cavity?
It is a mold found in nature that causes:
2. otitis externa
3. allergic bronchopulmonary aspergillosis (ABPA)
If it colonizes an old TB cavity if forms "fungus balls" which can cause hemoptysis or become invasive.
What patients are most likely to be infected by aspergillus?
1. neutropenic patients
What assay is used in cases of suspected invasive aspergillus?
Galactomannan antigen assay- quantitative assay done on BAL or blood which confirms a fungal cell wall (galactomannan).