Molecular characterization of carbapenem-resistant Enterobacteriaceae at a tertiary care laboratory in Mumbai

Abstract

Carbapenem-hydrolyzing β-lactamases are increasingly reported worldwide, leading to therapeutic failure. In an era where the drug development pipeline is stagnant, it is crucial to preserve current classes of antibiotics to help fight against infection caused by multidrug-resistant organisms (MDROs), by practicing a rational approach for the use of antibiotics. Identifying the mechanisms of resistance gives us much needed insights in this field. A total of 113 consecutive, non-duplicate carbapenem-resistant clinical isolates were collected from July to December 2012. These isolates were subjected to the modified Hodge test (MHT) for phenotypic detection of carbapenemases, an inhibitor-based test employing EDTA for the detection of metallo-β-lactamase (MBL), and phenylboronic acid for the detection of Klebsiella pneumoniae carbapenemase (KPC). A multiplex polymerase chain reaction (PCR) assay that characterized the five most predominant carbapenemases (bla NDM, bla OXA, bla VIM, bla IMP, bla KPC) was designed. The 113 isolates consisted of Klebsiella spp. (46), Enterobacter spp. (32), Escherichia coli (31), Citrobacter spp. (2), Proteus spp. (1), and Morganella spp. (1). bla NDM-1 was the most prevalent carbapenemase and accounted for 75.22 % (85/113) of the isolates. This was followed by bla OXA [4.42 % (n = 5)]. 18.5 % (21/113) of the isolates possessed dual carbapenemase genes. 98.9 % concordance was observed between the phenotypic tests and the molecular tests for the detection of MBL. In conclusion, patients infected with resistant bacteria require early appropriate antimicrobial treatment for good clinical outcome. Thus, identifying the resistant mechanisms of suspected pathogens becomes crucial. Also, the high incidence of plasmid-mediated bla NDM-1 calls for the implementation of strict infection control and contact isolation precautions in order to prevent the spread of these organisms.

Carbapenem-Resistant Acinetobacter baumannii and Enterobacteriaceae in South and Southeast Asia

“…Carbapenem resistance rates in Enterobacteriaceae have been more variable than those in CRAB in India, but longitudinal studies have shown dramatic increases in resistance rates over time (10,53,(62)(63)(64)(65)(66)(67)(68)(69)(70)(71). NDM remains consistently the major carbapenemase found in Enterobacteriaceae in that country (72). CP-CRE have been identified in the environment in the community since 2010 (14,73), likely as a consequence of sanitation issues.…”

Intestinal Carriage of Carbapenemase-Producing Organisms: Current Status of Surveillance Methods

“…KPCs were initially detected in a clinical isolate in 1996 in North Carolina; since then, 19 variants have been discovered (21)(22)(23)(24). KPC has been found in a variety of Enterobacteriaceae, including Klebsiella spp., Escherichia coli, Enterobacter spp., Citrobacter spp., Morganella spp., Serratia marcescens (25)(26)(27)(28)(29), Raoultella spp. (30), Kluyvera (31), and Salmonella (32), and in non-Enterobacteriaceae such as Aeromonas (33), Pseudomonas, and Acinetobacter baumannii (34).…”

Antibiotic resistance: What is so special about multidrug-resistant Gram-negative bacteria?

“…An alarming finding from a molecular characterization study of carbapenem-resistant Enterobacteriacea in Mumbai, West India, revealed that 18.5% (21/113) of the clinical isolates investigated possessed dual carbapenemase genes [34]. Moreover, recently a series of 24 cases of colistin-resistant Klebsiella pneumoniae has been reported from a new oncology center at Kolkata.…”