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Karthikeyan Kumarasamy

Bio: Karthikeyan Kumarasamy is an academic researcher from University of Madras. The author has contributed to research in topics: Acinetobacter & Colistin. The author has an hindex of 7, co-authored 7 publications receiving 3768 citations.

Papers
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Journal ArticleDOI
TL;DR: The prevalence of NDM-1, in multidrug-resistant Enterobacteriaceae in India, Pakistan, and the UK is investigated, and co-ordinated international surveillance is needed.
Abstract: Summary Background Gram-negative Enterobacteriaceae with resistance to carbapenem conferred by New Delhi metallo-β-lactamase 1 (NDM-1) are potentially a major global health problem. We investigated the prevalence of NDM-1, in multidrug-resistant Enterobacteriaceae in India, Pakistan, and the UK. Methods Enterobacteriaceae isolates were studied from two major centres in India—Chennai (south India), Haryana (north India)—and those referred to the UK's national reference laboratory. Antibiotic susceptibilities were assessed, and the presence of the carbapenem resistance gene bla NDM-1 was established by PCR. Isolates were typed by pulsed-field gel electrophoresis of XbaI-restricted genomic DNA. Plasmids were analysed by S1 nuclease digestion and PCR typing. Case data for UK patients were reviewed for evidence of travel and recent admission to hospitals in India or Pakistan. Findings We identified 44 isolates with NDM-1 in Chennai, 26 in Haryana, 37 in the UK, and 73 in other sites in India and Pakistan. NDM-1 was mostly found among Escherichia coli (36) and Klebsiella pneumoniae (111), which were highly resistant to all antibiotics except to tigecycline and colistin. K pneumoniae isolates from Haryana were clonal but NDM-1 producers from the UK and Chennai were clonally diverse. Most isolates carried the NDM-1 gene on plasmids: those from UK and Chennai were readily transferable whereas those from Haryana were not conjugative. Many of the UK NDM-1 positive patients had travelled to India or Pakistan within the past year, or had links with these countries. Interpretation The potential of NDM-1 to be a worldwide public health problem is great, and co-ordinated international surveillance is needed. Funding European Union, Wellcome Trust, and Wyeth.

2,680 citations

Journal ArticleDOI
TL;DR: The epidemiology of Klebsiella pneumoniae carbapenemases across continents is summarized, issues around detection, present antibiotic options and those in development, treatment outcome and mortality, and infection control are discussed.
Abstract: Klebsiella pneumoniae carbapenemases (KPCs) were originally identified in the USA in 1996. Since then, these versatile β-lactamases have spread internationally among Gram-negative bacteria, especially K pneumoniae, although their precise epidemiology is diverse across countries and regions. The mortality described among patients infected with organisms positive for KPC is high, perhaps as a result of the limited antibiotic options remaining (often colistin, tigecycline, or aminoglycosides). Triple drug combinations using colistin, tigecycline, and imipenem have recently been associated with improved survival among patients with bacteraemia. In this Review, we summarise the epidemiology of KPCs across continents, and discuss issues around detection, present antibiotic options and those in development, treatment outcome and mortality, and infection control. In view of the limitations of present treatments and the paucity of new drugs in the pipeline, infection control must be our primary defence for now.

1,314 citations

Journal ArticleDOI
TL;DR: The isolation of a strain of Klebsiella pneumoniae from a urine sample from a middle-aged patient admitted to the intensive care unit of a tertiary care hospital in Chennai, India in July 2010 showed wide-spectrum resistance to b-lactams, aminoglycoside, fluoroquinolones, co-trimoxazole, nitrofurantoin and tigecycline, but susceptibility to colistin and fosfomycin
Abstract: Sir, The emergence of NDM-1-producing isolates and their sources have been clearly identified in several countries worldwide. In particular, the blaNDM-1 gene was identified in various genera of Enterobacteriaceae and in non-fermenting Gram-negative bacilli from environmental samples in India. Furthermore, the increasing co-production of NDM-1 with other carbapenemases has been detected amongst isolates of Enterobacteriaceae and Acinetobacter sp. in many parts of India. – 7 We report here the isolation of a strain of Klebsiella pneumoniae (designated IR98) from a urine sample from a middle-aged patient admitted to the intensive care unit of a tertiary care hospital in Chennai, India in July 2010. Species identification and antibiotic susceptibility, determined using an automated system (VITEK-2, bioMerieux Inc.), showed wide-spectrum resistance to b-lactams, aminoglycoside, fluoroquinolones, co-trimoxazole, nitrofurantoin and tigecycline, but susceptibility to colistin and fosfomycin, according to CLSI guidelines. MICs of various antibiotics were determined using the agar dilution method, while the tigecycline MIC was determined using the broth microdilution method. European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were applied to interpret the susceptibilities. The isolate was highly resistant to imipenem (256 mg/L), meropenem (128 mg/L), ceftazidime (.256 mg/L), cefotaxime (.256 mg/L), amikacin (.512 mg/L), gentamicin (.512 mg/L), tobramycin (.512 mg/L), netilmicin (.512 mg/L), co-trimoxazole (.32 mg/L), ciprofloxacin (.32 mg/L) and tigecycline (4 mg/L), but remained susceptible to colistin (0.5 mg/L). The double-disc synergy test (DDST), modified Hodge test (MHT) and combined-disc synergy test (CDST) were used for the detection of metallo-b-lactamases (MBLs), other carbapenemases and KPC, or KPC with MBLs. The simultaneous production of MBL and KPC-like carbapenemases was confirmed by positive DDST, MHT and CDST with meropenem discs containing both EDTA and phenylboronic acid (PBA) or EDTA, while meropenem discs supplemented with PBA were negative. PCR assays for genes encoding b-lactamases and 16S rRNA methylases revealed the presence of blaNDM-1, blaKPC-2, blaCTX-M-15, blaSHV-12, blaTEM-1, blaOXA-1 and rmtB genes. Plasmid analysis using the Kieser technique revealed that K. pneumoniae IR98 harboured four plasmids, with sizes of 160, 120, 70 and 40 kb, using Escherichia coli NCTC 50192 as a reference. To study the transferability of these plasmids (encoding the resistance determinants), transconjugation and transformation experiments were performed using E. coli J53 (Azide-R) and E. coli TOP10 as recipient strains. Transconjugants were selected on MacConkey agar plates using sodium azide (200 mg/L) with ceftazidime (2 mg/L), meropenem (0.5 mg/L) or amikacin (20 mg/L). The plasmid extract of K. pneumoniae IR98 was transformed into E. coli TOP10, and transformants were selected on MacConkey agar plates containing 2 mg/L ceftazidime. Selected colonies were replica-plated onto MacConkey agar plates with or without meropenem (0.5 mg/L) or amikacin (20 mg/L). The genes encoding NDM-1, CTX-M15 and 16S rRNA methylase were transferred in conjugation experiments, whereas transfer of KPC-2 was successful only by transformation. The plasmids purified from the clinical isolate, transconjugants and transformants were typed by PCR-based replicon typing (PBRT). The E. coli J53-p98A transconjugant obtained from the meropenem plate showed an MBL phenotype and elevated MICs of all the b-lactams (except aztreonam) and susceptibility to non-b-lactam antibiotics. Plasmid analysis revealed that E. coli J53-p98A harboured a 160 kb plasmid that belonged to the Inc A/C type. Subsequently, this plasmid was found by PCR to carry the blaNDM-1 gene. In addition, the E. coli J53-p98B transconjugant grown on both ceftazidime and amikacin plates showed decreased susceptibility to aminoglycosides and cephalosporins except cefoxitin, and was positive for extendedspectrum b-lactamase (ESBL) production on DDST. Both blaCTX-M15 and rmtB genes were carried on a 120 kb IncF plasmid that was identified in E. coli J53-p98B. In contrast, the ESBL-negative transformant (E. coli TOP10-p98C) from both ceftazidime and meropenem plates was resistant to all the b-lactams except carbapenems (MICs 2 mg/L). The blaKPC-2 gene together with blaTEM-1 was carried on a 70 kb non-typeable plasmid that was identified in E. coli TOP10-p98C. Although the co-existence of blaNDM-1 with different carbapenemase genes has been reported in India, we believe this to be the first report of the co-occurrence of blaNDM-1 with blaKPC-2 and rmtB in a clinical isolate of K. pneumoniae from India. This co-production of NDM-1 with an unrelated carbapenemase and 16S RNA methylase results in very broad-spectrum antibiotic resistance profiles. The growing emergence of these powerful resistance mechanisms in India is cause for great concern as treatment options are virtually exhausted.

74 citations

Journal ArticleDOI
TL;DR: The gene is associated with the remnants of the Tn125 transposon normally associated with blaNDM-1 in Acinetobacter spp.
Abstract: NDM-1 probably emerged in Acinetobacter species prior to its dissemination among Enterobacteriaceae, and NDM-1-like enzymes are increasingly reported in Acinetobacter species. Here, we report on the genetic context of blaNDM-1 in the earliest known NDM-1-producing organisms, clinical isolates of Acinetobacter from India in 2005. These strains harbor blaNDM-1 plasmids of different sizes. The gene is associated with the remnants of the Tn125 transposon normally associated with blaNDM-1 in Acinetobacter spp. The transposon has been disrupted by the IS26 insertion and subsequent movement events.

50 citations

Journal ArticleDOI
TL;DR: In vitro data on plasmid transfer and stability suggest that p NDM-BJ01-like plasmids could have contributed to the spread of blaNDM-1 into Enterobacteriaceae.
Abstract: The blaNDM-1 gene is associated with extensive drug resistance in Gram-negative bacteria. This probably spread to Enterobacteriaceae from Acinetobacter spp., and we characterized plasmids associated with blaNDM-1 in Acinetobacter spp. to gain insight into their role in this dissemination. Four clinical NDM-1-producing Acinetobacter species strains from India and Pakistan were investigated. A plasmid harboring blaNDM-1, pNDM-40-1, was characterized by whole-genome sequencing of Acinetobacter bereziniae CHI-40-1 and comparison with related plasmids. The presence of similar plasmids in strains from Pakistan was sought by PCR and sequencing of amplicons. Conjugation frequency was tested and stability of pNDM-40-1 investigated by real-time PCR of isolates passaged with and without antimicrobial selection pressure. A. bereziniae and Acinetobacter haemolyticus strains contained plasmids similar to the pNDM-BJ01-like plasmids identified in Acinetobacter spp. in China. The backbone of pNDM-40-1 was almost identical to that of pNDM-BJ01-like plasmids, but the transposon harboring blaNDM-1, Tn125, contained two short deletions. Escherichia coli and Acinetobacter pittii transconjugants were readily obtained. Transconjugants retained pNDM-40-1 after a 14-day passage experiment, although stability was greater with meropenem selection. Fragments of pNDM-BJ01-like plasmid backbones are found near blaNDM-1 in some genetic contexts from Enterobacteriaceae, suggesting that cross-genus transfer has occurred. pNDM-BJ01-like plasmids have been described in isolates originating from a wide geographical region in southern Asia. In vitro data on plasmid transfer and stability suggest that these plasmids could have contributed to the spread of blaNDM-1 into Enterobacteriaceae.

40 citations


Cited by
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Journal ArticleDOI
TL;DR: The emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance, in Enterobacteriaceae and emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria.
Abstract: Summary Background Until now, polymyxin resistance has involved chromosomal mutations but has never been reported via horizontal gene transfer. During a routine surveillance project on antimicrobial resistance in commensal Escherichia coli from food animals in China, a major increase of colistin resistance was observed. When an E coli strain, SHP45, possessing colistin resistance that could be transferred to another strain, was isolated from a pig, we conducted further analysis of possible plasmid-mediated polymyxin resistance. Herein, we report the emergence of the first plasmid-mediated polymyxin resistance mechanism, MCR-1, in Enterobacteriaceae. Methods The mcr-1 gene in E coli strain SHP45 was identified by whole plasmid sequencing and subcloning. MCR-1 mechanistic studies were done with sequence comparisons, homology modelling, and electrospray ionisation mass spectrometry. The prevalence of mcr-1 was investigated in E coli and Klebsiella pneumoniae strains collected from five provinces between April, 2011, and November, 2014. The ability of MCR-1 to confer polymyxin resistance in vivo was examined in a murine thigh model. Findings Polymyxin resistance was shown to be singularly due to the plasmid-mediated mcr-1 gene. The plasmid carrying mcr-1 was mobilised to an E coli recipient at a frequency of 10 −1 to 10 −3 cells per recipient cell by conjugation, and maintained in K pneumoniae and Pseudomonas aeruginosa . In an in-vivo model, production of MCR-1 negated the efficacy of colistin. MCR-1 is a member of the phosphoethanolamine transferase enzyme family, with expression in E coli resulting in the addition of phosphoethanolamine to lipid A. We observed mcr-1 carriage in E coli isolates collected from 78 (15%) of 523 samples of raw meat and 166 (21%) of 804 animals during 2011–14, and 16 (1%) of 1322 samples from inpatients with infection. Interpretation The emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance. Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria. Funding Ministry of Science and Technology of China, National Natural Science Foundation of China.

3,647 citations

Journal ArticleDOI
TL;DR: Recent advances in understanding of the mechanisms by which bacteria are either intrinsically resistant or acquire resistance to antibiotics are reviewed, including the prevention of access to drug targets, changes in the structure and protection of antibiotic targets and the direct modification or inactivation of antibiotics.
Abstract: Antibiotic-resistant bacteria that are difficult or impossible to treat are becoming increasingly common and are causing a global health crisis. Antibiotic resistance is encoded by several genes, many of which can transfer between bacteria. New resistance mechanisms are constantly being described, and new genes and vectors of transmission are identified on a regular basis. This article reviews recent advances in our understanding of the mechanisms by which bacteria are either intrinsically resistant or acquire resistance to antibiotics, including the prevention of access to drug targets, changes in the structure and protection of antibiotic targets and the direct modification or inactivation of antibiotics.

2,837 citations

Journal ArticleDOI
TL;DR: These resistance traits have been identified among nosocomial and community-acquired infections and are being investigated for use in drug discovery and development.
Abstract: Carbapenemases increasingly have been reported in Enterobacteriaceae in the past 10 years. Klebsiella pneumoniae carbapenemases have been reported in the United States and then worldwide, with a marked endemicity at least in the United States and Greece. Metallo-enzymes (Verona integron–encoded metallo-β-lactamase, IMP) also have been reported worldwide, with a higher prevalence in southern Europe and Asia. Carbapenemases of the oxacillinase-48 type have been identified mostly in Mediterranean and European countries and in India. Recent identification of New Delhi metallo-β-lactamase-1 producers, originally in the United Kingdom, India, and Pakistan and now worldwide, is worrisome. Detection of infected patients and carriers with carbapenemase producers is necessary for prevention of their spread. Identification of the carbapenemase genes relies mostly on molecular techniques, whereas detection of carriers is possible by using screening culture media. This strategy may help prevent development of nosocomial outbreaks caused by carbapenemase producers, particularly K. pneumoniae.

2,044 citations

Journal ArticleDOI
28 Aug 2014
TL;DR: In this review the factors that have been linked to the waxing of bacterial resistance are addressed and profiles of bacterial species that are deemed to be particularly concerning at the present time are illustrated.
Abstract: Dangerous, antibiotic resistant bacteria have been observed with increasing frequency over the past several decades. In this review the factors that have been linked to this phenomenon are addressed. Profiles of bacterial species that are deemed to be particularly concerning at the present time are illustrated. Factors including economic impact, intrinsic and acquired drug resistance, morbidity and mortality rates, and means of infection are taken into account. Synchronously with the waxing of bacterial resistance there has been waning antibiotic development. The approaches that scientists are employing in the pursuit of new antibacterial agents are briefly described. The standings of established antibiotic classes as well as potentially emerging classes are assessed with an emphasis on molecules that have been clinically approved or are in advanced stages of development. Historical perspectives, mechanisms of action and resistance, spectrum of activity, and preeminent members of each class are discussed.

1,467 citations

Journal ArticleDOI
TL;DR: A rapid and reliable PCR-based technique was developed for detection of genes encoding carbapenemases belonging to different classes using optimized conditions, with PCR giving distinct amplicon sizes corresponding to the different genes for each mixture.

1,438 citations