Comparison of three biochemical tests for rapid detection of extended-spectrum β-lactamase-producing Enterobacteriaceae

Enterobacterial isolates producing clavulanic-inhibited extended-spectrum β-lactamases (ESBLs) are increasingly spreading in the community and are often responsible for nosocomial infections. Rapid biochemical tests have been developed recently for their detection. Three tests, namely the Rapid ESBL NDP test, the β-Lacta test and the Rapid ESBL Screen have been evaluated with a collection of 108 well-characterized strains including wild-type strains, strains producing ESBLs, overexpressed cephalosporinases, and carbapenemases. The ESBL NDP test and the Rapid ESBL Screen (a copy of the ESBL NDP test) are aimed to detect ESBL producers while the ß-Lacta test is aimed to detect not only ESBL producers but also cephalosporinase and carbapenemase producers. The sensitivity and specificity of detection of ESBL producers (n = 60) were 95% and 100% for the Rapid ESBL NDP test, 80% and 87% (after 30 min) and 92% and 83% (after 2 h) for the Rapid ESBL Screen, and 91% and 96% for the ß-Lacta test. Variable and time-consuming detection (up to 2h) of ESBLs by the Rapid ESBL Screen and concomittant and variable detection of producers of AmpC and several type of carbapenemases correspond to significant shortcomings for using the Rapid Screen ESBL and ß-Lacta tests, respectively