Predicting antibiotic resistance to community-acquired pneumonia antibiotics in culture-positive patients with healthcare-associated pneumonia

Abstract

Objective: To develop and validate a model to predict resistance to community-acquired pneumonia antibiotics (CAP-resistance) among patients with healthcare-associated pneumonia (HCAP), and to compare the model's predictive performance to a model including only guideline-defined criteria for HCAP.

Design: Retrospective cohort study.

Setting: Six Veterans Affairs Medical Centers in the northwestern United States.

Patients: Culture-positive inpatients with HCAP.

Measurements: Patients were identified based upon guideline-defined criteria for HCAP. Relevant cultures obtained within 48 hours of admission were assessed to determine bacteriology and antibiotic susceptibility. Medical records for the year preceding admission were assessed to develop predictive models of CAP-resistance with logistic regression. The predictive performance of cohort-developed and guideline-defined models was compared.

Results: CAP-resistant organisms were identified in 118 of 375 culture-positive patients. Of guideline-defined criteria, CAP-resistance was associated (odds ratio (OR) [95% confidence interval (CI)]) with: admission from nursing home (2.6 [1.6-4.4]); recent antibiotic exposure (1.7 [1.0-2.8]); and prior hospitalization (1.6 [1.0-2.6]). In the cohort-developed model, CAP-resistance was associated with: admission from nursing home or recent nursing home discharge (2.3 [1.4-3.8]); positive methicillin-resistant Staphylococcus aureus (MRSA) history within 90 days of admission (6.4 [2.6-17.8]) or 91-365 days (2.3 [0.9-5.9]); cephalosporin exposure (1.8 [1.1-2.9]); recent infusion therapy (1.9 [1.0-3.5]); diabetes (1.7 [1.0-2.8]); and intensive care unit (ICU) admission (1.6 [1.0-2.6]). Area under the receiver operating characteristic curve (aROC [95% CI]) for the cohort-developed model (0.71 [0.65-0.77]) was significantly higher than for the guideline-defined model (0.63 [0.57-0.69]) (P = 0.01).

Conclusions: Select guideline-defined criteria predicted CAP-resistance. A cohort-developed model based primarily on prior MRSA history, nursing home residence, and specific antibiotic exposures provided improved prediction of CAP-resistant organisms in HCAP.