Bacterial pneumonia risk factors

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Arooj Naz, M.B.B.S

Overview

Bacterial pneumonia can affect individuals of any age, gender, or race and has minimal significance in relation to family history. Individuals with underlying immunoglobulin defects have a significantly higher likelihood of infection. Bacterial pneumonia tends to affect men more often than women, and is more common in African Americans compared to Caucasians. Socioeconomic status is an important contributing factors and may explain the increased prevalence rate in low to middle-income nations. Pneumonia may also be affected by the use of medications such as proton pump inhibitors and ACE inhibitors. Immunocompromised patients requiring in-hospital treatment may develop nosocomial pneumonia but this can also present in seemingly healthy patients with prolonged durations of stay. A majority of nosocomial pneumonia will developed within 48 hours but some may present later on. The most common pathogens causing nosocomial pneumonia include Gram-positive cocci (e.g, Staphylococcus aureus, which includes methicillin-resistant S. aureus, and Streptococcus species) and Aerobic gram-negative bacilli (e.g. Pseudomonas Aeruginosa, Escherichia Coli, Klebsiella Pneumoniae, Enterobacter species, Acinetobacter species).

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Risk Factors

Common risk factors in the development of bacterial pneumonia include:

• Age; Infants and geriatric patients greater than 65 years
• Comorbidities
  • Diabetes
  • Chronic kidney disease
  • COPD
  • Asthma
  • Lung cancer
• Underlying Genetic conditions
  • Cystic Fibrosis
  • X-linked Agammaglobulinemia
  • Selective IgA deficiency
  • Common variable immunodeficiency
  • Immotile cilia syndrome
  • Kartagener's syndrome
• Smoking
• Excessive alcohol intake
• Post viral complication (often after an Influenza infection)
• Immunosuppresion (eg, HIV, use of corticosteroids that may be iatrogenic)
• Low socioeconomic status
• Males
• African Americans

Pneumonia in relation to other Drugs/ Other medications used:

• Atypical antipsychotics have been shown to increase the risk of pneumonia, especially in elderly individuals.
• Use of Acid Suppressing drugs (H2 blockers, proton pump inhibitors, and other antacids) may increase the risk of pneumonia.
• ACE inhibitors may be helpful in reducing the risk of pneumonia.

Risk Factors and specific bacterial microorganisms leading to Pneumonia:

Underlying Condition	Most Common Bacterial Microorganisms
Alcohol Abuse	Streptococcus Pneumoniae, oral anaerobes, Klebsiella Pneumoniae, Acinetobacter
Aspiration	Oral anaerobes, Gram-negative enteric bacteria
COPD	Haemophilus Influenzae, Pseudomonas Aeruginosa, Legionella, Streptococcus Pneumoniae, Moraxella Catarrhalis
Endotracheal Obstruction	Streptococcus Pneumoniae, oral flora anaerobes, Haemophilus Influenzae, Staphylococcus Aureus
Lung Abscess	Community-acquired MRSA, oral anaerobes, Atypical Mycobacteria
HIV	Streptococcus Pneumoniae, Haemophilus Influenzae
IV Drug Abuse	Staphylococcus Aureus, oral anaerobes, Streptococcus Pneumoniae
Smoking	Haemophilus Influenzae, Pseudomonas Aeruginosa, Legionella, Streptococcus Pneumoniae, Moraxella Catarrhalis
Structural Lung Diseases	Pseudomonas Aeruginosa, Burkholderia Cepacia, Staphylococcus Aureus
Avian Related	Chlamydia psittaci

Nosocomial Pneumonia:

While in the hospital, especially after surgical procedures when immunity may be affected, patients are at risk of acquiring infections, especially with certain strains of bacteria. Furthermore, patients with pre-existing comorbidities or risk factors and have a prolonged duration of stay at the hospital predisposing them to increased susceptibility. A majority of cases of nosocomial pneumonia occur after 48 hours or more. The most common pathogens causing pneumonia include:

• Gram-positive cocci (e.g, Staphylococcus aureus, which includes methicillin-resistant S. aureus, and Streptococcus species)
• Aerobic gram-negative bacilli (e.g. Pseudomonas Aeruginosa, Escherichia Coli, Klebsiella Pneumoniae, Enterobacter species,  Acinetobacter species)