Abstract

Resistance to broad spectrum β-lactams mediated by AmpC and metallo beta-lactamases (MBLs) enzymes is a rising problem worldwide. The wide dissemination of Gram negative bacteria harboring these enzymes represents a significant clinical threat during the last decade, which is mainly due to treatment failure and restriction of therapeutic options. This problem should be really estimated in our locality with special emphasis on immunocompromised patients. The aim of this study was to isolate Gram negative bacteria from differrent sites of infection among patients with hematological malignancy, and to examine those isolates for AmpC and MBLs production by phenotypic and genotypic methods. Seventy four Gram negative bacterial strains were isolated from 387 clinical samples collected from different infection sites. Those isolates were screened for the presence of AmpC and MBLs by modified three dimensional test and Imipenem–EDTA combined disc test, respectively. Multiplex PCR was done as a confirmatory step for detection of AmpC and MBLs production by these isolates. Pseudomonas aeroginosa was the most common isolated Gram negative strain that was found to be positive for AmpC and MBL production. DHA gene was the most frequently detected AmpC β-lactamase gene, whereas VIM was the only detected MBL gene among the Gram negative bacterial isolates by multiplex PCR. The strong association found between AmpC production and MBL gene carriage is alarming which necessitate continuous surveillance of such resistance mechanisms among the Gram negative bacteria, especially in patients with hematological malignancy.

Key words: AmpC, metallo beta-lactamase (MBL), multiplex polymerase chain reaction, Pseudomonas aeroginosa.