18: Respiratory Infections

Question 1

What is pneumonia?

Answer 1

• Infection of alveoli in lungs with an immune response causing signs/sx
• Classifications:
  
  • CAP
  • Hospital-acquired (HAP)
  • Healthcare-assoc’d (HCAP)
  • Ventilator-assoc’d (VAP)
• # 1 worldwide infectious cause of death (followed by diarrhea, AIDS, TB)
• Most common organism: strep pneumoniae
• General risk factors: old/young age, altered mental status (dementia, alcohol, intubation), immunosuppression (AIDS, primary, drug-ind, chemo), smoking, lung disease (COPD, CF, Kartagener’s)
• Modes of aspiration: microaspiration, macroaspiration, hematogenous (tricuspid endocarditis), direct spread

Question 2

List the common microbial causes of CAP in:

1. Infants
2. Children
3. Adults

Answer 2

1. GBS, GNRs, Listeria
2. Pneumococcus (strep pneu), viruses, pertussis, atypical, H. flu
3. Pneumococcus, atypical, H. flu

Question 3

List the environmental factors and their corresponding suspected pathogens causing pneumonia.

Answer 3

1. Caves, bats, OH and MS rivers: Histoplasma capsulatum
2. Pigeon droppings: Cryptococcus neoformans
3. Parrots: Chlamydophila psittaci
4. Southwestern US: Coccidiodes immitis
5. Farm animals, parturient cats: Coxiella burnetii
6. Cruise ships, hotel, plumbing: Legionella
7. ICU: Pneumococcus, staph aureus, legionella, GNRs

Question 4

List common signs/symptoms of pneumonia.

Answer 4

• Complaints: dyspnea, fever, cough, chills, chest pain, myalgia, headache
• History: age, co-morbidities, sick contacts, unusual exposures, travel, social
• PEX: altered mental status, rales, tactile fremitus (palpable vibration), decreased breath sounds, rhonchi (course rattling), grunting, nasal flaring
• Radiology: S. pneumonia (lobar), s. aureus (multilobar/abscess), mycoplasma (diffuse interstitial)

Question 5

For sterptococcus pneumoniae:

1. Microbiology
2. Virulence Factors
3. Diagnosis
4. Treatment
5. Vaccine?

Answer 5

1. GPD, oval/lancet-shaped
2. Polysaccharide capsule (90 types; most common = 6, 14, 18, 19, 23); IgA protease; pneumolysin
3. Blood/sputum culture, urine antigen test, gram stain
4. PCN (ampicillin) or cephalosporins (ceftriaxone); fluoroquinolone, vancomycin, macrolide, linezolid
5. 23-valent for at-risk adults (Pneumovax), 13-valen for children (Prevnar)

Question 6

For mycoplasma:

1. Microbiology
2. Virulence Factors
3. Diagnosis
4. Treatment
5. Vaccine?

Answer 6

1. No cell wall (not visible on gram stain); membrane contains sterols not present in other bacteria
2. TLR2 for binding epithelium, P1 for attachment; remains extracellular; acts as superantigen
3. Serology (IgG) or PCR
4. Macrolides (erythromycin, azithromycin, clarithromycin), fluoroquinolones (levofloxacin)

NB: Atypical, “walking pneumonia”

Question 7

For chlamydophila:

1. Microbiology
2. Virulence Factors
3. Diagnosis
4. Treatment
5. Vaccine?

Answer 7

1. Intracellular parasite; uses host ATP; trilaminar outer membrane; 3 types: trachomatis (meternal to fetal transmission; staccato-like cough, rapid respiratory rate, afebrile), pneumoniae (child and elderly; sore throat, chronic cough, afebrile), psittaci (parrot exposure; fever, rash, neuro sx)
2. Two-phase life cycle: Elementary body (infx), reticulate body (divides by binary fission in host)
3. Serology: 4-fold rise in titer
4. Erythromycin for trachomatis, macrolide, doxycycline or levofloxacin for pneumoniae, doxy, tetra, eryth for psittaci
5. None

Question 8

For Legionella:

1. Microbiology
2. Virulence Factors
3. Clinical
4. Diagnosis
5. Treatment
6. Vaccine?

Answer 8

1. Legionella pneumophila and micdadei; GNR, poorly staining
2. Flagellae, pili, phagosome evasion, intracellular replication, exotoxins –> microabscesses
3. Fever (105), rigors, cough, HA, multilobular infiltrates, microabscesses, diarrhea, abdominal pain, nausea, high WBC
4. Urine antigen detection assay: EIA; serology >1:128 (late dev of abb)
5. Macrolide or levofloxacin
6. None

Question 9

For Bordatella pertussis:

1. Microbiology
2. Virulence Factors
3. Clinical
4. Diagnosis
5. Treatment
6. Vaccine?

Answer 9

1. GNC; pertussis, parapertussis, holmseii
2. Pertussis toxin, heat-labile toxin
3. Apnea, cyanotic spells, fever, cough
4. Culture (special order on Bordet-Gengou), PCR

NB: Known as “whooping cough”