Phenotypic Detection of Metallo (3-Lactamase in Carbapenem Resistant Gram Negative Bacilli Isolates

AbstractBackground: A rising threat of the rapid spread of acquired metallo (3-lactamases (MBLs) among Gram Negative Bacilli (GNB) is a matter of public health concern worldwide. Hence, detection of MBLs producing clinical isolates via an accurate and cost effective technique is necessary to prevent their dissemination as well as regulation of antimicrobial steward-ship policy. This study aimed to detect MBLs in Carbapenem Resistant Gram Negative Bacilli (CRGNB) using two pheno-typic tests; Combined Disc Test (CDT) and Double Disc Synergy Test (DDST).Methods: We conducted a prospective study on 130 GNB isolates recovered from different clinical specimens collected from different patients. Isolates were identified then antibiotic susceptibility profile was determined by VITEK® 2 compact system. GNB which showed resistance to meropenem were screened for MBLs production by CDT and DDST.Results: Out of 36 CRGNB isolates, 23 isolates (63.9%) were MBLs positive by CDT, and 20 (55.6%) by DDST. With almost perfect agreement between CDT and DDST.Conclusion: Our study validates two phenotypic methods (CDT and DDST) for the detection of MBLs production, making them highly applicable to routine clinical laboratories.