Nosocomial Outbreak Due to Extended-Spectrum-Beta-Lactamase- Producing Enterobacter cloacae in a Cardiothoracic Intensive Care Unit

Abstract

Enterobacter cloacae has been associated with several outbreaks, usually involving strains that overproduce chromosomal ␤-lactamase or, uncommonly, strains expressing extended-spectrum ␤-lactamases (ESBL). Only sporadic cases of ESBL-producing E. cloacae have been identified in our hospital in recent years. We describe the epidemiology and clinical and microbiological characteristics of an outbreak caused by ESBL-producing E. cloacae in a cardiothoracic intensive care unit (CT-ICU). Prospective surveillance of patients with infection or colonization by ESBL-producing E. cloacae among patients admitted to the CT-ICU was performed during the outbreak. Production of ESBL was determined by decreased susceptibility to expanded-spectrum cephalosporins and a positive double-disk test result. Clone relatedness was determined by pulsed-field gel electrophoresis (PFGE). From July to September 2005, seven patients in the CT-ICU with ESBL-producing E. cloacae were identified (four males; median age, 73 years; range, 45 to 76 years); six patients had cardiac surgery. Four patients developed infections; three had primary bacteremia, one had ventilator-associated pneumonia, and one had tracheobronchitis. ESBLproducing E. cloacae showed resistance to quinolones and aminoglycosides. PFGE revealed two patterns.

The continuing challenge of ESBLs

“…Not detecting ESBLs in these pathogens may have a significant adverse impact on patients, especially those treated with extended-spectrum cephalosporins [68,69]. ESBLs are more difficult to detect in these organisms because AmpC enzymes may be induced by clavulanate (which inhibits them poorly) and may increase resistance to cephalosporins, overcoming the synergy arising from inhibition of the ESBL [70].…”

Cultivation of Enterobacter Hormaechei from Human Atherosclerotic Tissue

“…plasmids 24,25) . E. cloacae have been identified in outbreaks, usually involving strains that overproduce beta-lactamase, including a nosocomial outbreak in a cardiothoracic intensive care unit 26) . It would be interesting to test serum samples for anti-E. hormaechei antibody titers; however, healthy tissue segments could only be obtained postmortem and therefore serum was not available.…”

Method for Phenotypic Detection of Extended-Spectrum Beta-Lactamases in Enterobacter Species in the Routine Clinical Setting

“…No guidelines have been issued for extended-spectrum betalactamase (ESBL) detection in members of the Enterobacteriaceae with inducible chromosomal AmpC beta-lactamases, such as Enterobacter spp., although these species may cause hospital outbreaks (7,9,10), are frequently multidrug resistant (MDR) (9,10), and may constitute a reservoir for plasmidmediated ESBLs (3,12,13) for other Enterobacteriaceae species. The absence of such recommendations likely has two reasons.…”