Community Acquired Pneumonia Hospital-Acquired Pneumonia
Typical Atypical non-VAP HAP VAP
Definition Acute infection of the pulmonary parenchyma acquired outside of the hospital Acquired ≥48 hours after hospital admission Acquired ≥48 hours after endo
Etiology - S. pneumoniae → #1 cause - Mycoplasma pneumoniae ● S. aureus Highly resistant strains of:
- H. influenzae - Chlamydia pneumoniae ● P. aeruginosa ● P. aeruginosa
- M. catarrhalis - Legionella pneumophila ● Enterobacter ● Enterobacter spp.
- S. aureus - Mycobacterium tuberculosis ● Klebsiella ● MRSA
- S. pyogenes - Coxiella burnetii ● E. coli ● Acinetobacter
- Aerobic gram(-): E. coli, Klebsiella Viral pneumonia → >50% in kids, ¼ in adults ● Acinetobacter ● E. coli
- Anaerobic bacteria → aspiration In AIDS & immunocompromised pxs: ● B. cepacia ● Klebsiella
● Non-tb mycobacteria ● Higher incidence of S. ● Stenotrophomonas
● Pneumocystis jirovecii & other fungi pneumoniae than VAP CF → Pseudomonas & staph
Epidemiology Risk Risk for illness, severity, & Risk factors for specific pathogens: For MDR pathogens: ● Critical illness
factors atypical pathogens - Contaminated water → Legionella ● IV antibiotic use in previous 90 ● Poor nutrition
- Older age (>65) → ↑anaerobes - Poor dental hygiene, aspiration → days ● Sedation
- Chronic comorbidities anaerobes ● Prolonged hospitalization ● Immobilization
- Viral RTI - Influenza infection → S. aureus ● Hemodialysis ● Factors that affect ment
- Impaired airway defenses - COPD → S. pneumoniae, H. influenzae, ● Poor functional status For MDR pathogens:
- Smoking and alcohol overuse M. catarrhalis ● Severe pneumonia ● Prolonged hospitalization b
- Crowded living conditions - Caves & bat droppings → Histoplasma ● Prior antibiotic use (90 day
- Low income settings - Diabetes → Klebsiella ● ↑ frequency of antibiotic res
- Exposure to environmental toxins - Southwestern USA & northwestern unit
Loss of consciousness → gram(-) Mexico → coccidioidomicosis ● Immunosuppression
→ Additive risk ● Patient's severity
● Prolonged mechanical vent
Pathophysiology Transmission via person-person, droplets, or aerosol - 24-48 hours after hospital admission → patient microbiota starts
1. Nasopharynx colonization - Factors in hospital patients that predispose to pneumonia
2. Microaspiration → lung colonization - Immunosuppression
3. Immunocompromise OR large inoculum → infection - Supine position
4. Inflammation & virulence factors → lung parenchymal damage - Surgery and anesthesia
Exogenous insults (smoking, viral infection) may change lung microbiota & favor - Length of hospital stay → Change of microbiota
bacterial growth - ↑ resistance of hospital pathogens
Specific virulence factors - Patients w/o aspiration rarely present anaerobic pathogens
- Influenza virus → reduces mucus secretion speed (until 12 weeks post infection) - ↓ severity : ↑ likelihood of non-nosocomial pathogens: S. pneum
- H. influenzae → direct cilia damage & M. catarrhalis
- S. pneumoniae → proteases against IgA ⇥ phagocytosis (also by capsule) → Microaspirations
- Mycoplasma → breaks off cilia Endotracheal tube ⇥ ciliary clearance & cough, → biofilm formation
Older & immunocompromised pxs are less likely to exhibit typical symptoms despite
Clinical Features etiological agent. - ↑ in basal lung areas
- Histological heterogeneity → patchy inflammation
Abrupt onset Insidious onset - From bronchiolitis to bronchopneumonia to frank abscess, even within
- Productive cough - Nonproductive, dry cough
Typical Atypical non-VAP HAP VAP
Definition Acute infection of the pulmonary parenchyma acquired outside of the hospital Acquired ≥48 hours after hospital admission Acquired ≥48 hours after endo
Etiology - S. pneumoniae → #1 cause - Mycoplasma pneumoniae ● S. aureus Highly resistant strains of:
- H. influenzae - Chlamydia pneumoniae ● P. aeruginosa ● P. aeruginosa
- M. catarrhalis - Legionella pneumophila ● Enterobacter ● Enterobacter spp.
- S. aureus - Mycobacterium tuberculosis ● Klebsiella ● MRSA
- S. pyogenes - Coxiella burnetii ● E. coli ● Acinetobacter
- Aerobic gram(-): E. coli, Klebsiella Viral pneumonia → >50% in kids, ¼ in adults ● Acinetobacter ● E. coli
- Anaerobic bacteria → aspiration In AIDS & immunocompromised pxs: ● B. cepacia ● Klebsiella
● Non-tb mycobacteria ● Higher incidence of S. ● Stenotrophomonas
● Pneumocystis jirovecii & other fungi pneumoniae than VAP CF → Pseudomonas & staph
Epidemiology Risk Risk for illness, severity, & Risk factors for specific pathogens: For MDR pathogens: ● Critical illness
factors atypical pathogens - Contaminated water → Legionella ● IV antibiotic use in previous 90 ● Poor nutrition
- Older age (>65) → ↑anaerobes - Poor dental hygiene, aspiration → days ● Sedation
- Chronic comorbidities anaerobes ● Prolonged hospitalization ● Immobilization
- Viral RTI - Influenza infection → S. aureus ● Hemodialysis ● Factors that affect ment
- Impaired airway defenses - COPD → S. pneumoniae, H. influenzae, ● Poor functional status For MDR pathogens:
- Smoking and alcohol overuse M. catarrhalis ● Severe pneumonia ● Prolonged hospitalization b
- Crowded living conditions - Caves & bat droppings → Histoplasma ● Prior antibiotic use (90 day
- Low income settings - Diabetes → Klebsiella ● ↑ frequency of antibiotic res
- Exposure to environmental toxins - Southwestern USA & northwestern unit
Loss of consciousness → gram(-) Mexico → coccidioidomicosis ● Immunosuppression
→ Additive risk ● Patient's severity
● Prolonged mechanical vent
Pathophysiology Transmission via person-person, droplets, or aerosol - 24-48 hours after hospital admission → patient microbiota starts
1. Nasopharynx colonization - Factors in hospital patients that predispose to pneumonia
2. Microaspiration → lung colonization - Immunosuppression
3. Immunocompromise OR large inoculum → infection - Supine position
4. Inflammation & virulence factors → lung parenchymal damage - Surgery and anesthesia
Exogenous insults (smoking, viral infection) may change lung microbiota & favor - Length of hospital stay → Change of microbiota
bacterial growth - ↑ resistance of hospital pathogens
Specific virulence factors - Patients w/o aspiration rarely present anaerobic pathogens
- Influenza virus → reduces mucus secretion speed (until 12 weeks post infection) - ↓ severity : ↑ likelihood of non-nosocomial pathogens: S. pneum
- H. influenzae → direct cilia damage & M. catarrhalis
- S. pneumoniae → proteases against IgA ⇥ phagocytosis (also by capsule) → Microaspirations
- Mycoplasma → breaks off cilia Endotracheal tube ⇥ ciliary clearance & cough, → biofilm formation
Older & immunocompromised pxs are less likely to exhibit typical symptoms despite
Clinical Features etiological agent. - ↑ in basal lung areas
- Histological heterogeneity → patchy inflammation
Abrupt onset Insidious onset - From bronchiolitis to bronchopneumonia to frank abscess, even within
- Productive cough - Nonproductive, dry cough
