Carbapenem Resistant Enterobacteriaceae: Risk Factors and Role of Extended Care Facilities

Background: Carbapenem resistant Enterobacteriacae (CRE) were first isolated in USA in the 1990’s, with subsequent strains identified worldwide. Presently, these multidrug-resistant organisms have been isolated in 32 states, and numbers are increasing as asymptomatic carriers migrate and more advanced diagnostic tools are developed. CRE have been isolated in blood, urine, genital tract, catheters, wounds and sputum. Their emergence has been linked to many factors: intensive care unit (ICU) or extended hospital stay, mechanical ventilation, poor functional status, and previous antibiotic use. Patients with CRE also have longer hospital stays and increased mortality, even when receiving appropriate antibiotic treatment. Due to limited treatment options, most interventions are currently being directed at prevention of transmission by early detection and contact precautions. Few address the epidemiology of confirmed cases.

Objective: The purpose of this study is to assess the risk factors for CRE infections in adults in an acute care hospital.

Methods: The hospital is a level I trauma center with 551 licensed beds, including 2 adult ICUs and a neonatal ICU. The study population included adults who were hospitalized from July 2008 through September 2010 and had positive cultures for CRE. Patient records were reviewed for co-morbidities, type and location of residence, presence of indwelling devices, antibiotic exposure prior to acquisition of CRE, signs and symptoms of infection, and mortality. The sites of positive cultures, microorganisms isolated, and antibiotic sensitivities were also evaluated.

Results: Twenty-six patients had 34 CRE positive cultures. Of the 26 cases: 23 (88.5%) were infected and 3 (11.5%) were colonized. Of the 23 infected patients 10 (43.5%) had two sites of infection. Sites of positive cultures included urine (19), blood (6), sputum (5), wound (3), and PEG tube (1). Three (13%) infected cases died during their hospitalization, all from CRE bacteremia. Four cases (15.4%) were hospital associated. Of the 26 cases, 23 (88.5%) resided in an extended care facility (ECF): 15 (57.7%) nursing home, 7 (26.9%) long term acute care, 1 (3.8%) rehabilitation institution. Only 3 (11.5%) lived in a private residence. Of 12 patients who had a chronic indwelling urinary catheter, 10 (83.3%) presented with CRE in the urine. Of the 34 CRE isolates, 32 (94%) were K. pneumoniae, 1 (3%) E. coli and 1 (3%) P. mirabilis. Susceptibility data revealed: 88% were susceptible to colistin, 73.5% to gentamicin and 73.5% to tigecycline.

Conclusions: This study showed that patients in ECFs are at high risk for acquiring CRE. The ECFs were located throughout the Chicago metropolitan area. Chronic illnesses and indwelling devices were associated with acquisition of CRE infections, and mortality was greatest with bacteremia with a rate of 50%. Screening for CRE should be considered in areas of high CRE endemicity.