Extended-Spectrum β-Lactamase Resistance in the ICU

Abstract

Despite the recent focus on gram-positive infections in the intensive care unit (ICU), gram-negative resistance mechanisms continue to challenge the critical care practitioner. A recent national surveillance study of United States ICUs found Escherichia coli, Enterbacter species, Klebsiella species, and Pseudomonas aeruginosa represented 72% of all gram-negative bacilli recovered. E coli, Klebsiella pneumoniae, and Enterobacter species are significant producers of a β-lactamase that inactivates almost all β-lactam antibiotics, so-called extended-spectrum β-lactamases or ESBLs. Many clinical laboratories may not test for ESBL-production in these organisms, thus clinicians may be unaware of the rising incidence of this plasmid-mediated resistance mechanism. Since initial reports of ESBLs in the 1980s, investigators have found an association with ESBL-producing organisms and the critically ill population. Risk factors for ESBL-related infection in the ICU include arterial, central-venous, and urinary-catheters; mechanical ventilation; abdominal surgery; prior antibiotic therapy with ceftazidime or other extended spectrum cephalosporins; length of time in the ICU; and overall acuity of illness. This article reviews the emergence and epidemiology of the ESBL evolution, describes the clinical implications of ESBL production in the ICU, and outlines a strategy for management of infection in patients at risk for ESBL-producing organisms.