Risk factors for colonization with ampicillin and high-level aminoglycoside-resistant enterococci during hospitalization in the ICU and the impact of prior antimicrobial exposure definition: a prospective cohort study

Abstract

The aim of our prospective cohort study was to determine the incidence, genetic relatedness and risk factors for colonization with ampicillin and high-level aminoglycoside-resistant enterococci (ARHLARE) among patients hospitalized in the intensive care unit. During 15-month period, we included 105 patients. The only independent risk factor for ARHLARE colonization was days of cefotaxime/ceftriaxone therapy [odds ratio (OR): 1·13; 95% confidence interval (CI) 1·10–1·27; P  =  0·045]. Patients with higher total use of antibiotics, patients on prolonged mechanical ventilation, and patients with urinary tract infection (UTI), were also found to be at increased risk to become colonized with ARHLARE. Pulsed-field gel electrophoresis suggested multifocal origin of the majority of the colonizing strains. Our results show that an increase in total antibiotic consumption for 10 defined daily doses (DDD)/patient increased the odds of colonization with ARHLARE for 36%. Further efforts to optimize antimicrobial use in high risk patients are proposed.

Keywords:

• Antibiotic consumption
• Antimicrobial resistance
• Enterococci
• Nosocomial colonization
• Risk factors

We thank to all the patients who participated in this study, nurses from the ICU for collecting most of the surveillance samples, personnel in the microbiological laboratory for all the additional work they had to do, Tom Bajec for helping us with the computer work and Andrej Zejn for proofreading the manuscript.

This work was supported by the Young Researchers Project from the Slovenian Research Agency (3311-02-831459).