Risk Factor Evaluation for Methicillin-Resistant Staphylococcus aureus and Pseudomonas aeruginosa in Community-Acquired Pneumonia.

BACKGROUND: The 2019 community-acquired pneumonia guidelines recommend using recent respiratory cultures and locally validated epidemiology plus risk factor assessment to determine empirical coverage of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. OBJECTIVE: To develop a methodology for evaluating local epidemiology and validating local risk factors for P aeruginosa and MRSA. METHODS: This multicenter, retrospective cohort evaluated adult patients admitted for pneumonia. Risk factors for MRSA and P aeruginosa were evaluated using multivariable logistic regression and reported as adjusted odds ratios (aORs). RESULTS: There were 10 723 cases evaluated. Lung abscess/empyema had the highest odds associated with MRSA (aOR = 4.24; P < 0.0001), followed by influenza (aOR = 2.34; P = 0.01), end-stage renal disease (ESRD; aOR = 2.09; P = 0.006), illicit substance use (aOR = 1.7; P = 0.007), and chronic obstructive pulmonary disease (COPD; aOR = 1.26; P = 0.04). For P aeruginosa, the highest odds were in bronchiectasis (aOR = 6.13; P < 0.0001), lung abscess/empyema (aOR = 3.36; P = 0.005), and COPD (aOR = 1.84; P < 0.0001). Isolated COPD without other risk factors did not pose an increased risk of either organism. CONCLUSION AND RELEVANCE: Influenza, ESRD, lung abscess/empyema, and illicit substance use were local risk factors for MRSA. Bronchiectasis and lung abscess/empyema were risk factors for Pseudomonas. COPD was associated with MRSA and Pseudomonas. However, isolated COPD had similar rates of MRSA and Pseudomonas pneumonia compared with the total population. This study established a feasible methodology for evaluating local risk factors.