Risk factors for carbapenemase-producing organisms among inpatients in Scotland: A national matched case-control study

Abstract

Objective: To determine risk factors for carbapenemase-producing organisms (CPOs) and to determine the prognostic impact of CPOs.

Design: A retrospective matched case-control study.

Patients: Inpatients across Scotland in 2010-2016 were included. Patients with a CPO were matched with 2 control groups by hospital, admission date, specimen type, and bacteria. One group comprised patients either infected or colonized with a non-CPO and the other group were general inpatients.

Methods: Conditional logistic regression models were used to identify risk factors for CPO infection and colonization, respectively. Mortality rates and length of postisolation hospitalization were compared between CPO and non-CPO patients.

Results: In total, 70 CPO infection cases (with 210 general inpatient controls and 121 non-CPO controls) and 34 CPO colonization cases (with 102 general inpatient controls and 60 non-CPO controls) were identified. Risk factors for CPO infection versus general inpatients were prior hospital stay (adjusted odds ratio [aOR], 4.05; 95% confidence interval [CI], 1.52-10.78; P = .005), longer hospitalization (aOR, 1.07; 95% CI, 1.04-1.10; P < .001), longer intensive care unit (ICU) stay (aOR, 1.41; 95% CI, 1.01-1.98; P = .045), and immunodeficiency (aOR, 3.68; 95% CI, 1.16-11.66; P = .027). Risk factors for CPO colonization were prior high-dependency unit (HDU) stay (aOR, 11.46; 95% CI, 1.27-103.09; P = .030) and endocrine, nutritional, and metabolic (ENM) diseases (aOR, 3.41; 95% CI, 1.02-11.33; P = .046). Risk factors for CPO infection versus non-CPO infection were prolonged hospitalization (aOR, 1.02; 95% CI, 1.00-1.03; P = .038) and HDU stay (aOR, 1.13; 95% CI, 1.02-1.26; P = .024). No differences in mortality rates were detected between CPO and non-CPO patients. CPO infection was associated with longer hospital stay than non-CPO infection (P = .041).

Conclusions: A history of (prolonged) hospitalization, prolonged ICU or HDU stay; ENM diseases; and being immunocompromised increased risk for CPO. CPO infection was not associated with increased mortality but was associated with prolonged hospital stay.