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.
Highlights
Β-Lactamases are important components of the antimicrobial resistance in Gram negative bacteria
The strong association found between AmpC production and metallo beta-lactamases (MBLs) gene carriage is alarming which necessitate continuous surveillance of such resistance mechanisms among the Gram negative bacteria, especially in patients with hematological malignancy
AmpC was detected in 38 (51.3%) of the 74 Gram negative bacterial isolates which were studied in this research
Summary
Β-Lactamases are important components of the antimicrobial resistance in Gram negative bacteria. They are identified in these pathogens as well as their biochemical properties (Zavasci et al, 2010). Primarily hydrolyses cephems (cephamycins and cephalosporins) and hydrolyze penicillins and aztreonam. These enzymes are resistant to the currently available β-lactamase inhibitors such as clavulanate, sulbactam and tazobactam (Philippon et al, 2002). High level production of AmpC by Gram negative bacteria may cause resistance to the first, second and third-generation cephalosporins, penicillins, cephamycins and β-lactamase inhibitor combination. MBL producing Gram negative bacteria are typically resistant to aminoglycosides and fluoroquinolones, further compromising therapeutic options (Uma Karthika et al, 2009)
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