The Impact of Carbapenem Resistance on Resource Utilization in Enterobacteriaceae Infections

Background: Carbapenem-resistant Enterobacteriaceae (CRE) infections represent an emerging health care threat, resulting in excess morbidity and mortality. The purpose of this study is to estimate healthcare utilization and costs for CRE patients in the Intermountain Health Care (IHC) system.

Methods:Patients ≥18 years, admitted to an IHC facility from 2005-2015, submitting a culture to the microbiology lab were eligible for this study. Carbapenem-resistance was defined by CDC definition. Patient data were retrospectively abstracted from the IHC Data Warehouse. Each CRE case was matched to 4 non-resistant controls admitted the same year, with the same culture site, genus and species. Characteristics of study patients were compared using non-parametric methods.

Results: Of 176,902 patients eligible, 120 patients with CRE were identified. 45.8% CRE samples were isolated from urine, with Escherichia coli and Klebsiella pneumoniae(41.6%) the most common pathogens. Distribution of age (median 65 years), gender (50% male), and ethnicity (Caucasian 88%) were similar across the two groups, with a trend toward older age among CRE cases (p=0.08). Approximately half (52.5%) were cultured in the Salt Lake City area, with most (89.2%) from larger health care facilities (p=0.00001). Facility transfer was a more common admission source for CRE patients (vs clinic or ER, 13.3% vs 9.7%, p=0.12).

Extreme severity of illness per the APR-DRG mortality score was more common in CRE patients than controls (43.7% vs 31.7%, p=0.008). Median Charlson Comorbidity Index (5 vs 4, p=0.0001) was also higher. Median total antimicrobial days of therapy for CRE was 14 (range: 1,286), 7 more than controls (p<0.0001). In-hospital mortality (15.0% vs 8.3%, p=0.04), median total cost of hospitalization ($30,910.38 vs $18,098, p<0.0001) and length of stay after CRE identification (16.8 days vs 8.2 days p=0.04) were nearly twice that of controls. While readmission rates were similar, CRE patients were more likely to be discharged to post-acute care facilities than controls (15.0% vs 8.8%, p=0.02).

Conclusion: CRE infections are complicated by high patient acuity and antibiotic resistance, resulting in significantly higher health care costs, antimicrobial use, and mortality.