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Microbiology > L28-30: Bacterial Infections of the Respiratory Tract > Flashcards

L28-30: Bacterial Infections of the Respiratory Tract Flashcards

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1
Q

Characteristics of lower respiratory tract infections (LRTI)

A

Less common than URTI but more severe, includes pertussis, bronchitis, and pneumonia

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2
Q

Airway defenses

A

Ciliated epithelium and mucociliary escalator

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3
Q

General features of bacterial pneumonia

A

Inflammation of the lung as a result of bacterial infection, causes fever, malaise, cough and crackles, pleuritic chest pain, dyspnea, and potentially sputum production

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4
Q

Those at increased risk to pneumonia

A

Comorbidities (heart disease, diabetes, lung disease/cancer, immunosuppression), age extremes, smoking/alcohol/narcotics

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5
Q

Pathogenesis of bacterial pneumonia

A

Bacteria enter small airways or alveoli and grow in rich lung environment; local effects are due to inflammatory immune response to bacteria; can cause accumulation of fluid, bacteria, neutrophils, and fibrin

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6
Q

Typical/lobar pattern of CXR and what causes it

A

Alveoli are full of bacteria (consolidation occurs in one lung), associated with S. pneumo, S. aureus, H. influenzae, and most G- bacteria

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7
Q

Atypical/patchy pattern of CXR and what causes it

A

Mostly all of the lobes of the lung are involved, not entire lung is full, associated with M. pneumoniae, C. pneumoniae, and L. pneumophila (special pattern)

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8
Q

Characteristics of typical (“lobar”) pneumonia

A

Sudden onset, patient looks sick, productive cough, bloody sputum, fever of 103-104 oF, consolidation and pleurisy, WBC count elevated (typically neutrophils), most commonly caused by S. pneumoniae

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9
Q

Characteristics of atypical (“patchy”) pneumonia

A

Onset is gradual, patient looks well, nonproductive cough, scant/watery sputum, no fever (usually), normal WBC count, most commonly caused by M. pneumoniae

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10
Q

Complications of pneumonia

A
  • -Pleural effusion (excess fluid buildup in pleural space)
  • -Anemia (with chronic) or thromboxytopenia
  • -With chronic: decrease in oxygen arterial pressure, weight loss/muscle atrophy, and bronchiectasis
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11
Q

Aspiration pneumonia

A

Introduction of foreign material into the bronchial tree (usually fluid with bacteria); associated with alcoholics, coma/stroke patients

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12
Q

Community acquired pneumonia (CAP)

A

Any pneumonia not acquired in a healthcare setting

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13
Q

Hospital acquired pneumonia (HAP)

A

Acquired in a healthcare setting, occurs more often in immunocompromised patients and associated with ventilator use (VAP) – frequently caused by MDR Gram- bacteria

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14
Q

Importance of labs with pneumonia

A

Elevated WBC count (“left shift”), blood culture (positive = severe disease), sputum analysis (>25 PMNS and <10 epithelial cells)

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15
Q

Streptococcus pneumoniae

A

Normal colonizer of URT but causes pneumococcal pneumonia, Gram+ diplococci, alpha-hemolytic, catalase-, many serotypes

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16
Q

Pneumococcal virulence factors

A
  • -Surface adhesins (colonize pharynx)
  • -IgA protease (cleaves IgA, prevents clearance)
  • -Pneumolysin*** (pore-forming toxin, colonization, invasion, inflammation, complement activation, etc.)
  • -Teichoic acid and peptidoglycan (inflammation)
  • -Thick polysaccharide capsule (antiphagocytic)
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17
Q

Lab diagnosis of S. pneumoniae

A

Gram+ sputum, alpha-hemolysis on blood agar, catalase-, bile solubility positive, optochin sensitive

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18
Q

Treatment for S. pneumoniae pneumonia

A

Empiric therapy of penicillin, azithromycin, or azithromycin + cephalosporin

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19
Q

Prevention of S. pneumoniae pneumonia

A

Vaccination with 23-valent pneumococcal polysaccharide vaccine or 13-valent conjugated-pneumococcal vaccine

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20
Q

Staphylococcus aureus

A

Normal microbiota in some, Gram+ cocci clusters, catalase+, coagulase+, protein A binds Fc portion of antibody

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21
Q

Panton-Valentine leukocidin (PVL)

A

Virulence factor of S. aureus; cyotoxin that causes severe necrosis of tissue that is irreversible

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22
Q

MRSA (methicillin resistant S. aureus)

A

Resistant to all beta-lactam antibiotics, harder to treat (more dangerous because less options for treatment)

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23
Q

1 causes of Gram- bacterial pneumonia

A

Klebsiella pneumoniae (facultative anaerobe), Pseudomonas aeruginosa (aerobe)

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24
Q

Gram- pneumonia characteristics

A

Generally an underlying disease, anaerobic bacterial etiology includes foul-smelling sputum, antibiotic resistance is HUGE

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25
Gram- pneumonia diagnosis and treatment
Can diagnose with sputum culture and Gram-staining, sometimes blood culture; treat with broad spectrum antibiotics and multiple drug therapy
26
Klebsiella pneumoniae
Gram- rod, non-motile, mucoid colonies, oxidase-, present in respiratory tract and occasionally feces
27
How does Klebsiella pneumoniae present?
Classic lobar pneumonia with bloody sputum
28
Virulence factors of Klebsiella pneumoniae
LPS and capsule
29
Pseudomonas aeruginosa
Gram- rod, flagellated, obligate aerobe (sugar fermentation-), oxidase+, smells like grapes
30
Where does Psuedomonas aeruginosa grow?
Water, hand soaps (soap containers), dilute antiseptics (like at restaurants), humidifiers -- forms biofilms
31
Pseudomonas aeruginosa virulence factors
- -Toxin A (ribosylates EF-2) - -Leukocidin (targets leukocytes) - -Phospholipase C (membrane disruption) - -Capsule (anti-phagocytic) - -Pyocyanin - -Pyoverdin
32
Treatment for Pseudomonas aeruginosa
Antipseudomonal penicillin (ticarcillin or piperacillin) + aminoglycoside (gentamycin, tobramycin, amikacin)
33
Correlation between Psuedomonas aeruginosa and CF
Most common cause of death in this population -- cystic fibrosis patients have a significantly impaired mucociliary escalator, so when strains convert from non-mucoid to mucoid there are significant effects and it is almost impossible to eradicate
34
Causes of walking pneumonia
Mycoplasma pneumoniae, Chlamydophila pneumoniae, Chlamydophila psittaci, Coxiella burnetti
35
Cause of toxic pneumonia
Legionella pneumophila
36
Symptoms of atypical pneumonia
Bronchopneumonia with gradual onset (fever, headache, fatigue, muscle ache, dry cough, scant/watery sputum)
37
Treatment of atypical pneumonia
Tetracycline and erythromycin (empiric therapy for atypical pneumonia)
38
Mycoplasma pneumoniae
One of the smallest bacteria, pleomorphic, no peptidoglycan, membrane contains sterols, restricted to humans, low infectious dose transmission by respiratory droplets
39
Virulence factor of Mycoplasma pneumoniae
P1 adhesin (binds to base of cilia to cause ciliostasis --> epithelial cell damage/death --> defect in mucociliary clearance)
40
Diagnosis of Mycoplasma pneumoniae
Cold agglutinin test (when RBCs agglutinate at 4 oC), PCR, serology, culture and microscopy not recommended
41
Treatment for Mycoplasma pneumoniae and Chlamydophila pneumoniae
Tetracycline and macrolide (erythromycin), NOT beta-lactams!
42
Chlamydophila pneumoniae
Gram-, obligate intracellular, causes atypical pneumonia
43
Diagnosis of Chlamydia pneumoniae
Microimmunofluorescence and PCR
44
Life cycle of Chlamydophila pneumoniae
Elementary body (EB) attaches and enters cytoplasm, then forms reticulate body (RB) which undergoes binary fission and divides, then releases EBs from cell
45
2 types of disease caused by Legionella pneumophila
1. Legionnaires' disease (rare, requires antibiotics) | 2. Pontiac fever (not much known)
46
Legionella pneumophila
Gram-, coccobacilli inside cells and pleomorphic outside, difficult to culture, grows outside in water sources (parasites of amoebas)
47
Transmission of Legionella pneumophila
Aerosols from man-made water supplies -- outbreaks are associated with cooling towers/air conditioning and old buildings
48
Virulence/pathogenesis of Legionella pneumophila
1. Target and attach to alveolar macrophage using pili, flagella, and other proteins 2. Enter macrophage in endocytic vacuole (coiling phenomenon) 3. Hijacks cell and replicates
49
Clinical manifestation of Legionella pneumophila
Severe toxic pneumonia, causes myalgia, headache, rapidly rising fever, dry cough, etc. -- patchy infiltrates on CXR and elevated WBC count -- patient becomes progressively ill over 3-6 days
50
Diagnosis of Legionella pneumophila
Culture, direct fluorescent antibody (DFA), nucleic acid amplification test (NAAT)
51
Treatment of Legionella pneumophila
NOT beta-lactams, macrolide or fluoroquinolone is best
52
Mycobacteria cell wall
Recognize these terms: membrane, peptidoglycan, arabinogalactan, lipoarabinomannin, mycolic acids, mycolic acid-associated glycopipids
53
What causes tuberculosis?
Mycobacterium tuberculosis
54
Transmission of TB
Only in humans, person-to-person transmission via respiratory aerosol droplets (coughs, sneezes, speaking, singing)
55
Process of infection with TB
- -Mtb is inhaled into lungs and enters alveoli - -Mtb is taken up and multiplies within alveolar macrophages; lymphocytes are recruited - -Mtb can't be killed so granulomas form around it
56
How does latent TB infection occur?
The immune system is unable to kill Mtb and surrounds Mtb-infected macrophage to form a granuloma -- necrotic
57
What occurs with primary TB infection?
Usually asymptomatic and can lead to clearance, active TB (in immunosuppressed individuals), or latent TB (most individuals) that can reactivate
58
Cell-mediated immunity in TB
Causes most of the damage/pathology from TB but also can control it
59
Disseminated TB infection
Granuloma formation, also called miliary or extrapulmonary TB
60
Active TB symptoms
Gradual onset, variable manifestations including fatigue, weight loss*, weakness, fever, night sweats*, chest pain and dyspnea -- cough*
61
Reactivation TB symptoms
Similar to/same as active TB
62
Diagnosis of TB
- -CXR (Ghon focus: lung lesion seen on CXR as granuloma calcifies, Ghon complex: lung lesion and calcification seen together in hilar lymph) - -Rapid lab tests - -Must be reported immediately
63
Lab diagnosis of TB
- -Tuberculin skin test: ID injection of PPDs from Mtb cell wall looking for immune reaction (BCG vaccine = positive test) - -IFN-y release assay: blood sample tested for IFN-y release with Mtb - -Microscopy: acid-fast stains (not definitive), nucleic acid amplification tests, culture -- less useful
64
Treatment of TB
Drug cocktail including isonaizid
65
Vaccine for TB
BCG vaccine (Mycobacterium bovis), not common in US and not completely protective
66
TB and AIDS
TB infection risk, progression to active TB, and reactivation risk all much greater in HIV+ individuals; drug-resistant strains common -- leading causes of premature death in the world
67
Nontuberculous Mycobacteria
- -Mycobacterium avium-intracellulare (like TB, immunocompromised or those with lung disease) - -Mycobacterium kansasii (common in elderly)
68
Laryngitis, tracheitis, and epiglottitis basic info
Symptoms: hoarseness, burning retrosternal pain Causes: most likely viral, less common are GAS, Haemophilus influenzae, and S. aureus
69
Characteristics of Haemophilus influenzae serotype B (HiB)
Gram- coccobacilli, requires NAD and hemin, typed strains based on capsule and nontypeable but B has polysaccharide capsule of PRP (important)
70
Transmission of HiB and most susceptible population
Transmitted by respiratory droplets or direct contact; mostly pediatric
71
Virulence factors of HiB
LPS, IgA protease, PRP
72
Diagnosis of HiB
Gram staining and culture of blood, nasopharyngeal swab, sputum, etc.
73
Treatment of HiB
Broad-spectrum cephalosporin if severe, amoxicillin if less severe (also there is vaccine)
74
Common cause of acute bacterial bronchitis
Mycoplasma pneumoniae -- adhesin/receptor combo, can also cause pneumonia
75
Common cause of pertussis/whooping cough
Bordetella pertussis
76
Characteristics of Bordetella pertussis
Gram- coccobacilli, highly susceptible to toxic metabolites, adheres to ciliated respiratory mucosa and produces toxic factors, makes it hard to breathe due to paroxysmal cough and patients can become cyanotic
77
Progression of symptoms of pertussis
7-10 days = no symptoms 1-2 weeks = rhinorrhea, malaise, fever, sneezing (like common cold) -- MOST COMMUNICABLE 2-4 weeks = repetitive cough with whoops, vomiting, leukocytosis 3-4 weeks+ = diminished cough, secondary complications
78
Major adhesins in pertussis
B. pertussis mainly binds to ciliated epithelial cells using these: filamentous hemagglutinin***, peractin, fimbrae
79
Major toxins in pertussis
Activation of adenylate cyclase --> increase cAMP --> increase in respiratory secretions --> paroxysmal cough: pertussis toxin*** (AB toxin), adenylate cyclase/hemolysin toxin, LPS
80
Diagnosis of pertussis
Culture, nucleic acid amplification test, microscopy
81
Treatment of pertussis
Supportive therapy and macrolides (Z-packs and clarithromycin)
82
Vaccine for pertussis
DTap (contains detoxified pertussis toxin)

Microbiology (20 decks)

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