Background: We thought to determine whether extended spectrum β-lactamases (ESBLs) and AmpC β-lactamases (derepressed and inducible) ,alone or in combination,could be detected in clinical isolates of the Enterobacteriaceae using a simple, overnight disc diffusion test. Methods: 178 of 400 Enterobacterial isolates were included according to selection criteria: resistance to third generation cephalosporins (CPD) & (CTX) and to cephamycins (FOX). A scheme for detecting these resistance mechanisms phenotypically using Approximation (DDST, induction test) and combined (clavulanate and boronic) confirmatory tests and E-test strip. Results and Conclusion: By screening tests ESBLs were suspected in 178/400 (44.5%), AmpC were suspected in 98/400 (24.5%). By DDST ESBLs were confirmed in 173/276 (62.7%) while in combined clavulanate test ESBL alone were found in only 2 isolates while 253/276(91.7%) were found to be ESBL in presence of AmpC. AmpCs were detected by the combined clavulanate method in 64/276 (23.2%) and by combined boronic method in 65/276 (23.5%). Comparing these results to the gold standard E-test combined clavulanate method found to be a reliable method (sensitivity 100% &PPV 96%) in relation to the approximation method DDST (sensitivity 64.7% & specificity 83.3%).