Infections of lower respiratory tract - Kozel Flashcards
1
Q
What is Bronchitis?
A
inflammation of the large and mid-sized airways, due primarily to viral infections
2
Q
What is Bronchiolitis?
A
inflammation of the bronchioles, the smaller air passages, infection is primarily viral - 50-90% by RSV
3
Q
What is acute pneumonia?
A
Inflammation of the lungs caused by microbial inception of the alveoli and surrounding lung - present for days. Typically bacterial.
4
Q
What is atypical pneumonia?
A
Characterized by moderate amounts of sputum, absence of physical findings of consolidation, only moderate elevation of WBC’s and lack alveolar exudates. Mycoplasma is a major source of this.
5
Q
What is chronic pneumonia?
A
Inflammation of lungs caused by microbial infection of the alveoli and surrounding lung or non-infecious causes; present for weeks to months
6
Q
What are Pleural effusion and Empyema?
A
accumulation of pus in the pleural cavity
7
Q
What is a bacterial lung abscess?
A
infection causing necrosis of the lung parenchyma
8
Q
Cystic fibrosis leads to increased risk of…?
A
Lower respiratory tract infections.
9
Q
What factors contribute to the development of pneumonia?
A
- Defect in host defenses
- Exposure to particularly virulent microbe - ie. Influenza
- Overwhelming inoculum - exposure to high doses can overwhelm normal defenses
- Can involve one or more of the above
10
Q
What structures of the nasopharynx provide defense for the pulmonary system?
A
- nasal hair
- anatomy of upper airway
- presence of mucocilliary apparatus
11
Q
What structures of the oropharynx provide defense for the pulmonary system?
A
- saliva
- cough
- bacterial interference - normal flora keep pathogens from taking hold
12
Q
What structures of the trachea and bronchi provide defense for the pulmonary system?
A
- cough, epiglottal reflexes
- mucocilliary apparatus
- airway surface liquid - has lysozyme (targets cell wall of gram positives) and lactoferrin (iron chelator)
13
Q
What structures of the terminal airways and alveoli provide defense for the pulmonary system?
A
- alveolar lining fluid - contains surfactant, fibronectin, iron-binding proteins
- alveolar macrophages
- neutrophil recruitment
14
Q
How does alteration in level of consciousness impair pulmonary defenses?
A
Stroke, seizure, drugs, anesthesia and alcohol abuse all alter consciousness. This can compromise epiglottic closure leading to aspiration of oropharyngeal flora. Microbes in the mouth are often anaerobes and are often gram negatives so can lead to pneumonia and especially to abscesses.
15
Q
How does cigarette smoke impair pulmonary defenses?
A
- disrupts mucociliary function
2. disrupts macrophage activity
16
Q
How does alcohol abuse impair pulmonary defenses?
A
- impairs cough and epiglottic reflexes
- increased colonization of oropharynx with gram-negative bacilli
- decreased cellular responses
17
Q
How does infection with M. pneumonia, H. flu or viruses impair pulmonary defenses?
A
- interfere with or destroy cilia
2. causes defective cell function
18
Q
Why are older patients at increased risk for pulmonary infections?
A
- increased number and severity of underlying diseases
- less effective mucociliary clearance and coughing
- increased micro aspiration
- immune senescence
19
Q
What types of underlying diseases can increase risk of pulmonary infection?
A
- COPD
- immune deficiencies
- asplenia - especially associated with decreased clearance of strep pneumo
- functional asplenia can occur too - ie. with sickle cell disease
20
Q
Name the microbes associated with community-acquired acute pneumonia.
A
In order of importance:
- Strep pneumo
- legionella pneumophila
- klebsiella pneumoniae
- H. flu
- Staph aureus
- Pseudomonas
21
Q
Name the microbes associated with community acquired atypical pneumonia.
A
In order of importance:
- mycoplasma pneumophila
- Chlamydia species - C. pneumonia, C. psittaci and C. trachomatis
22
Q
Name the microbes associated with hospital acquired pneumonia.
A
In order of importance:
- Klebsiella
- Legionella
- pseudomonas species
- staph aureus
23
Q
Name the microbes associated with chronic pneumonia.
A
In order of importance:
- Nocardia
- mycobacterium
- tuberculosis and atypical mycobacteria
- Histoplasma capsulatum
- coccidioides immitis
- Blastomyces dermatitidis
24
Q
Name the microbes associated with necrotizing pneumonia and lung abscess.
A
In order of importance:
- klebsiella
- staph aureus
25
Name the microbes associated with pneumonia in an immune compromised host.
In order of importance:
1. pneumocystis jiroveci
2. mycobacterium avium-intracellulare
26
Name the microbes associated with aspiration pneumonia.
Anaerobic oral flora admixed with aerobic bacteria.
27
Name some infectious agents that cause pneumonia that infect via environmental exposure.
1. legionanaires - via exposure to contaminated aerosols such as air coolers
2. anthrax - exposure to goat hair, raw wool and animal hides
3. brucellosis - ingestion of unpasteurized milk
4. histoplasmosis - exposure to bat or bird droppings
5. leptospirosis - exposure to water contaminated with animal urine
6. hantavirus - exposure to rodnt droppings, urine or saliva
7. anthrax, plague, tularemia - potential bioterrorism exposure
28
What are some zoonotic exposures that can cause pneumonia?
1. brucellosis - employment as abattoir work or veterinarian
2. antrhax, brucellosis - exposure to cattle, goats, pigs
3. plague - exposure to ground squirrels, chipmunks, rabbits, prairie dogs and rats in Africa or SW US
4. tularemia- hunting or exposure to rabbits, foxes or squirrels or bites from flies or ticks
5. Psittacosis - exposure to birds
6. Q fever via Coxiella burnetii - exposure to infected goats, cattle, sheep, domestic animals (dogs and cats) and their secretions
7. Pasteurella multocida - exposure to infected dogs and cats
29
What are some potential travel exposures that may be an etiology for pneumonia?
1. coccidioidomycosis - exposure in San Joaquin valley, S. CA, SW Texas, S. AZ and New mexico
2. Histoplasmosis and blastomycosis - exposure in Mississippi or Ohio river valleys, Caribbean, central america or africa
3. SARS, avian flu - exposure in china
4. MERS -CoV - exposure in Arabian peninsula
5. Melioidosis - exposure in SE asia, West indies, australia or guam
30
Describe the pathogenesis of cystic fibrosis.
1. Lung obstructed by viscous secretions
| 2. Persistent bacterial infection produces airway wall damage
31
What microbes are associated with infection in cystic fibrosis?
1. staph aureus
2. pseudomonas
3. burkholderia cepacia complex
4. H. flu
5. other bacteria, anaerobes, fungi and viruses
32
What treatments are there for infection in cystic fibrosis?
1. remove viscous and purulent airway secretions
2. control bacterial infection with antibiotics
3. provide proper nutrition for host defense
33
What are some diagnostic tests to help evaluate pneumonia?
1. examination and culture of sputum
2. fiber-optic bronchoscopy
3. examination and culture of pleural effusions
4. blood culture, serology (looks for antibodies so good for chronic), urine studies including antigen detection
5. radiology
34
What is the gold standard for making a clinical diagnosis of pneumonia?
Radiology
35
What is the most common cause of bacterial pneumonia and meningitis?
Strep pneumo
36
Describe the characteristics of pneumococcal pneumonia.
1. abrupt onset, sharp pleural pain, bloody rusty sputum
2. largely a disease of a compromised host - age, physical condition, genetic (sickle cell disease)
3. generally localized in lower lobes - lobar pneumonia
37
What is the major antigen associated with strep pneumo?
Capsular polysaccharide. This is a T independent antigen. The capsule includes C polysaccharide or teichoic acid. THis cell wall carbohydrate reacts with acute phase protein (C-reactive protein)
38
What are some other virulence factors of strep pneumo?
1. Pneumolysin - a porin similar to Streptolysin O; contributes to inflammation
2. peptidoglycan and lipoteichoic acid - these are cell wall components. They activate the alternative pathway, they elicit production of IL-1 and TNF -a and are largely responsible for inflammation
39
How is strep pneumo differentiated from strep viridans?
Streptococcus pneumoniae is alpha hemolytic, optochin sensitive and bile soluble. Strep viridans is alpha hemolytic, catalase negative, optochin resistant.
40
What serologic tests can be used to identify strep pneumo?
Testing for free antigen (C polysaccharide) in body fluids.
41
What is the treatment for strep pneumo infection?
1. penicillin or ceftriaxone - drug of choice if susceptible
| 2. if resistant then use vancomycin, macrolides, doxycycline or a quinolone.
42
What is the mechanism of resistance of strep pneumo to penicillin or Beta-lactams?
Acquisition of penicillin binding proteins with reduced affinity for antibiotic.
43
What is Klebsiella pneumoniae?
A gram negative, encapsulated, lactose-fermenting rod.
44
What diseases does Klebsiella cause?
1. Pneumonia – necrotic destruction of alveolar spaces (mostly in a hospital setting)
2. Thick, bloody mucoid sputum
3. Patients are usually compromised
Immune suppressed
Impaired respiratory defenses
4. Other infections
UTI – second most common cause among elderly after E. coli
Wound infection
Bacteremia and meningitis
45
What is the key virulence factor of Klebsiella?
Polysaccharide capsule.
46
What is negative stain?
A special stain that can be used on Klebsiella to visualize it's capsule. Growing Klebsiella results in thick mucoid colonies.
47
How is Klebsiella identified in the lab?
1. sample of sputum, blood, pus or CSF
2. isolated on a typical enteric medium (designed specifically for growth of gram negative rods)
3. is identified by characteristics - fermenter, mucoid colonies, grows on enteric media
48
What is an API strip?
A test used to determine if a microbe is a fermenter. There are lots of carbohydrates on the strip and these turn yellow in the presence of fermenters.
49
How are Klebsiella infections treated?
Often Polymyxins (targets outer membranes of gram negative rods) because it is resistant to many antibiotics. Treatment is dependent on susceptibility testing.
50
Describe the resistance of Klebsiella.
1. carbapenem-resistant Klebsiella - encoded by bla gene
2. can hydrolyze all known beta lacatam antibiotics
3. resistant to beta lactamase inhibitors
51
What is Legionella pneumophila?
A thin pleomorphic gram negative rod. Replicates inside macrophages or amoebae's in nature. Can replicate inside a macrophage because it can prevent phagolysosome fusion and avoid death.
52
What does Legionella need to grow on agar?
Cysteine and iron. Are generally grown on enteric agar such as MacConkey agar.
53
What diseases does Legionella cause?
1. Legionaires disease
| 2. pontiac fever - mild respiratory infection, no pneumonia, self limiting and low mortality
54
What is Legionnaires disease?
A severe, acute pneumonia. Presents with fever, non-productive cough and SOB. Has a high mortality rate - 15-20%
55
What are some risk factors associated with Legionnaires disease?
1. 50 years or older
2. current or former smokers
3. chronic lung disease such as COPD and emphysema
4. weakened immune system, diabetes, kidney failure, immunosuppression
56
Describe the pathogenesis of Legionnaires disease.
1. Inhale infectious aerosol
2. Infects alveolar macrophages, monocytes and alveolar epithelial cells
3. Inhibition of phagolysosomal fusion prevents exposure to superoxide, H2O2 and OH radicals
4. Intracellular proliferation
5. Inflammatory response
6. Eventually, cell-mediated immunity
57
How is Legionnaires disease diagnosed?
1. X-ray or physical exam
2. sputum or endotracheal aspirate
3. not sensitive to conventional microscopy
4. requires special media to culture - needs iron and cysteine
5. Urinary antigen test - MOST commonly used diagnostic tool
6. Direct fluorescence antibody
7. nucleic acid amplification assays
58
The urinary antigen test used for diagnosis of Legionnaire's disease only picks up what serogroup?
Serogroup 1. This is the serogroup that is involved in 80-90% of community acquired infections.
59
How is Legionella transferred?
Acquired by exposure to contaminated aerosols - free cooling towers, hot tubs, water misters etc.
60
What are some issues with diagnosis of Legionnaires disease?
1. susceptibility tests not done due to difficulty of growing bacterium
2. many antibiotics ineffective due to poor penetration of macrophages
61
What is the treatment of Legionnaires disease?
1. macrolides - azithromycin, clarithromycin
2. floroquinolones - levofloxacin, moxifloxacin
3. tetracycline - doxycycline
62
What is the smallest free- living bacterium?
Mycoplasma
63
Describe some characteristics of Mycoplasma.
1. lack a cell wall so are resistant to antibiotics that target cell walls
2. cell membrane contains sterols (i.e.. cholesterol) that are obtained from host
3. growth in culture requires medium such as animal serum that contains sterols
64
Would penicillin, cephalosporins or vancomycin work on a mycoplasma infection?
No. These antibiotics target the cell wall and mycoplasma does not have a cell wall.
65
Describe the pathogenesis of mycoplasma.
1. Adheres to respiratory epithelium via an attachment organelle
- P1 protein is primary adhesin
- Receptors on host cells
2. Destroys cilia, then ciliated epithelial cells themselves
3. Irritation and secondary infection cause persistent cough
66
What diseases are caused by mycoplasma?
Most infection is asymptomatic.
1. tracheobronchitis - most common and presents with low-grade fever, myalgia, headache and non-productive cough
2. primary atypical pneumonia - patients are not terribly ill (why called walking pneumonia), presents with patchy bronchopneumonia on chest radiograph
67
How is mycoplasma infection diagnosed?
Usually diagnosed empirically on basis of clinical presentation:
1. microscopy - not useful due to poor staining
2. culture - not common because takes 2-6 weeks to grow and is not sensitive
3. nucleic acid amplification - not widely available
4. serology - can use a cold agglutinin test but this is not common because it lacks sensitivity and specificity
68
What is the cold agglutinin test?
Mycoplasma infection causes formation of IgM antibodies that are cross reactive with I blood group antigen on RBC's. Agglutination will only occur at low temps - 4 degrees C
69
What is the treatment for mycoplasma infection?
1. macrolides - azithromycin used most commonly but also erythromycin
2. tetracycline (also doxycycline) - cheap and effective but cannot be used in children
3. fluoroquinolone - very effective but expensive
70
What is Histoplasma capsulatum?
A dimorphic fungi that has two varieties:
1. H. capsulatum - capsulatum variety
2. H. capsulatum - duboisii variety
71
What is Coccidioides?
A dimorphic fungi that has two types:
1. coccidioides immitis
2. coccidioides posadasii
72
What is Blastomyces dermatitis?
A dimorphic fungi.
73
Blastomyces and histoplasma are both endemic where?
The Ohio and Mississippi river valleys.
74
Describe the pathophysiology of histoplasma capsulatum.
1. Inhalation of microconidia
2. Germination into yeasts
3. Intracellular growth in lungs
4. May remain localized or disseminate
75
Where can histoplasma capsulatum (capsulation variety) be found?
It inhabits soil with high nitrogen content such as soil with bat and bird droppings. It can be found in:
1. Ohio and Mississippi river valleys
2. Mexico, Central and South America - AIDS is a major risk factor in these areas
76
Where can histoplasma capsulatum (duboisii variety) be found?
It inhabits soil with high nitrogen content such as soil with bat and bird droppings. It can be found in:
1. tropical areas of Africa
