Abstract
The rapid spread of acquired metallo-beta-lactamases (MBLs) among major Gram-negative pathogens is an emerging threat and a matter of particular concern worldwide. This descriptive study was conducted between January and August 2009 in the department of Microbiology, Army Medical College, National University of Sciences and Technology, Rawalpindi, to determine the frequency and susceptibility patterns of MBL-producers among carbapenem-resistant Gram-negative rods (GNRs) from clinical isolates of a tertiary care hospital. All clinical samples were processed according to standard microbiological methods. Isolated GNRs were subjected to susceptibility testing against various antibiotics by disc diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Carbapenem-resistant isolates were subjected to the detection of MBL production by the E-test MBL strip method. Out of 50 carbapenem resistant isolates, 39 (78%) of were confirmed to be MBL producers by the E-strip method. Acinetobacter baumannii were the most frequent MBL producers, followed by Pseudomonas aeruginosa. A total of 19 (37%) of the MBL producers were susceptible to cefoperazone-sulbactam. The findings strongly suggest that there is a need to track the detection of MBL producers and that judicious use of carbapenems is necessary to prevent the further spread of these organisms.
Highlights
The rapid spread of acquired metallo-beta-lactamases (MBLs) among major Gram-negative pathogens is an emerging threat and a matter of particular concern worldwide
All these methods are based on the ability of metal chelators such as Ethylenediaminetetraacetic acid (EDTA) and thiol-based compounds to inhibit the activity of MBLs
From a total of 2347 samples 1,430 consecutive non duplicate Gram-negative bacilli were recovered (61%) Isolated Gram-negative rods were subjected to antimicrobial sensitivity testing per the Clinical and Laboratory Standards Institute (CLSI) guidelines
Summary
The rapid spread of acquired metallo-beta-lactamases (MBLs) among major Gram-negative pathogens is an emerging threat and a matter of particular concern worldwide. Methodology: This descriptive study was conducted between January and August 2009 in the department of Microbiology, Army Medical College, National University of Sciences and Technology, Rawalpindi, to determine the frequency and susceptibility patterns of MBLproducers among carbapenem-resistant Gram-negative rods (GNRs) from clinical isolates of a tertiary care hospital. Isolated GNRs were subjected to susceptibility testing against various antibiotics by disc diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Carbapenem-resistant isolates were subjected to the detection of MBL production by the E-test MBL strip method. Results: Out of 50 carbapenem resistant isolates, 39 (78%) of were confirmed to be MBL producers by the E-strip method. The introduction of carbapenems into clinical practice marked a great advance for the treatment of serious bacterial infections caused by beta-lactam-resistant bacteria [9]. Resistance to extended-spectrum beta-lactams has been frequently observed in non-fermenting bacilli such as Pseudomonas aeruginosa and Acinetobacter spp. These tests include the double disc synergy tests using various combinations such as EDTA with imipenem (IPM) or ceftazidime (CAZ) [10,11,12]; 2-mercaptopropionic acid with CAZ or IPM [15]; the Hodge test [12,13]; a combined disk test using EDTA with CAZ or IPM [14,15,16]; the MBL Etest (AB BioDisk) [17]; and a micro dilution method using EDTA and 1,10-phenanthroline with IPM [18]
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