Objcetive To evaluate three routine methods for detection of extended-spectrum β-lactamases(ESBLs). Methods Three routine
methods disk test, double-disk enhancement test and double-disc synergy test were applied to detect 30 ESBLs-producing and 50 non-ESBLs producing strains of Gram
negative bacilli and also to determine the situation of strains producing ESBLs among 65 strains of Gram negative bacilli isoluted from clinical samples.Results The sensitivity of three routine
methods disk test a double disk enhanmcement test and double-disk synergy test, was found to be 93.3%,86.7% and 93.3% respectively and their specificity 90.0%,100.0% and 100.0% respectively. The detectable rate of ESBLs in isolates of Gram negative bacilli was 15.4%.Conclusions Three routine methods are all suitable for detecting ESBLs, but the double-disk synergy test is the most sensitive and reliable among three routine methods for the detection of ESBLs in Gram negative bacilli, and more suitable for screening strains producing ESBLs routinely in all hospitals.