Method for Phenotypic Detection of Extended-Spectrum Beta-Lactamases

In 271 Enterobacter blood culture isolates from 12 hospitals, extended-spectrum beta-lactamase (ESBL) prevalence varied between 0 % and 30 % per hospital. High prevalence was associated with dissemination, indicating the potential relevance of infection control measures. Screening with cefepime or Vitek 2, followed by a cefepime/cefepime-clavulanate Etest, was an accurate strategy for ESBL detection in Enterobacter isolates (positive predictive value, 100%; negative predictive value, 99%). No guidelines have been issued for extended-spectrum beta-lactamase (ESBL) detection in members of the Enterobacteri-aceae 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 plasmid-mediated ESBLs (3, 12, 13) for other Enterobacteriaceae spe-cies. The absence of such recommendations likely has two reasons. First, phenotypic detection of ESBLs in members of the Enterobacteriaceae coexpressing an AmpC beta-lactamas