Rationale: The 2016 guidelines for hospital-acquired pneumonia (HAP) suggest applying a universal antibiogram resistance threshold in addition to patient criteria to determine empiric coverage. The impact of these recommendations is unknown.Objectives:1) Describe national antibiotic use and microbiology patterns for HAP among patients with noninfectious admissions, 2) measure the predictive performance of the antibiogram threshold and risk factors, and 3) estimate the change in practice with guideline implementation.Methods: We conducted a retrospective analysis of all hospitalizations without initial infection but with secondary pneumonia diagnoses at Veterans Affairs Medical Centers between October 1, 2012, and September 30, 2015. For each hospitalization we extracted: presence of methicillin-resistant Staphylococcus aureus (MRSA) and resistant gram-negative rods (R-GNR) in cultures, anti-MRSA and antipseudomonal antimicrobial administration, and facility-level prevalence of MRSA and R-GNR. We calculated the percentage of hospitalizations with resistant organisms, broad-spectrum antibiotics, and the predictive performance of patient characteristics and prevalence thresholds for MRSA.Results: Among 3,562 cases, 5.17% were positive for MRSA and 2.30% for R-GNR. The recommended MRSA prevalence threshold was 100.00% sensitive (95% confidence interval [CI], 98.02-100.00%) and 0.03% specific (95% CI, 0.00-0.16%) for MRSA-positive culture, leading to overtreatment of 94.81% (95% CI, 94.02-95.50%) of patients. Pressor order (odds ratio [OR], 3.89; 95% CI, 1.17-12.91) and intravenous antibiotics within the past 90 days (OR, 1.98; 95% CI, 1.03-3.81) were associated with MRSA. Mechanical ventilation was associated with R-GNR (OR, 4.37; 95% CI, 1.52-12.57).Conclusions: The guideline-recommended antibiogram threshold and characteristics did not improve prediction of MRSA or R-GNR and would have led to an increase in MRSA treatment.
Keywords: antibiograms; hospital-acquired pneumonia; resistance.