Bacteremia in previously hospitalized patients: prolonged effect from previous hospitalization and risk factors for antimicrobial-resistant bacterial infections.

Study Objective: Patients who came from the community but were recently discharged from the hospital have a higher risk of contracting antimicrobial-resistant bacterial infections. Our objectives are to determine the time from previous hospital discharge that affects subsequent antimicrobial susceptibility pattern and risk factors for antimicrobial-resistant infection in bacteremia in recently discharged patients.

Methods: Excluding patients of hospital-acquired, patients with regular health care-associated exposure, and patients whose previous hospitalization was not at our hospital, a total of 789 nonduplicated bacteremia episodes from community adult patients were enrolled in a 1-year study period. Antimicrobial-resistant bacteria, including multidrug-resistant gram-negative bacilli, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci causing bacteremia, were logistically analyzed according to different posthospitalization periods (3 to 90 days, 91 to 180 days, 181 to 360 days, and no hospitalization in the past 360 days) to identify the independent effect from previous hospitalization on subsequent antimicrobial-resistant bacteremia.

Results: Of the 789 bacteremia patients, the proportion of antimicrobial-resistant bacteremia is 14.6% (95% confidence interval [CI] 9.8% to 19.4%) for 3 to 90 days, 9.6% (95% CI 1.6% to 17.6%) for 91 to 180 days, and 6.4% (95% CI 0% to 13.4%) for 181 to 360 days since last hospitalization and 1.0% (95% CI 0.1% to 1.9%) for no hospitalization within the last 360 days. Risk of antimicrobial-resistant bacteremia decreased monthly after discharge by an odds ratio of 0.83 (95% CI 0.76 to 0.90) (P<.01). Previous carriage of antimicrobial-resistant bacteria in the past 360 days and previous stay at ICU in the past 180 days were independent risk factors for antimicrobial-resistant bacteremia in previously hospitalized patients.

Conclusion: Previous hospitalization affects the antimicrobial susceptibility of subsequent bacteremia up to 360 days after hospital discharge. Presence of risk factors for antimicrobial-resistant bacteremia in previously hospitalized patients may help emergency physicians in selecting empirical antimicrobial agents and prompting infection control precautions.