Mohibur Rahman1, Chiranjay Mukhopadhyay2, Ravi Prakash Rai1, Sanjay Singh1, Shefali Gupta1, Avinash Singh1, Ashutosh Pathak1, Kashi Nath Prasad3. 1. Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014, India. 2. Department of Microbiology, Kasturba Medical College, Manipal, Karnataka, India. 3. Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014, India. Electronic address: knprasad@sgpgi.ac.in.
Abstract
OBJECTIVES: Carbapenem resistance mediated by New Delhi metallo-β-lactamase 1 (NDM-1) and its variants has caused a major public-health concern worldwide. Here we report for the first time an Escherichia coli isolate positive for a novel variant (NDM-11). METHODS: blaNDM genes were investigated in E. coli by PCR and sequencing, and blaNDM variants were further characterised. The susceptibility pattern of novel blaNDM-11 towards different antimicrobials was compared with blaNDM-1 by cloning and expression in E. coli TOP10. RESULTS: A total of 33 carbapenem-resistant E. coli isolates were screened by PCR for the presence of blaNDM, of which 15 (45.5%) were positive. Sequencing of the PCR products revealed 10 isolates with NDM-1 and 5 isolates with NDM variants (one each of NDM-4, NDM-8 and NDM-11 and two NDM-5). Other resistance genes, including blaTEM-1, blaCTX-M-15, blaVIM, plasmid-encoded AmpC blaCMY-2 and 16S methyltransferases (rmtB and rmtC), were also associated with NDM variants in different combinations. The blaNDM variants were located on a transferable IncF-type plasmid of >100kb. Pulsed-field gel electrophoresis (PFGE) showed that all five E. coli isolates were unrelated, and multilocus sequence typing (MLST) revealed that they all belonged to ST131. Expression of the blaNDM-1 and blaNDM-11 genes in E. coli TOP10 showed no significant difference in MICs to various β-lactams, including carbapenems. CONCLUSIONS: This study underlines the spread of NDM variants with other antimicrobial resistance genes in E. coli in South India. It also describes a novel NDM variant (blaNDM-11) having an antimicrobial resistance pattern similar to blaNDM-1.
OBJECTIVES:Carbapenem resistance mediated by New Delhi metallo-β-lactamase 1 (NDM-1) and its variants has caused a major public-health concern worldwide. Here we report for the first time an Escherichia coli isolate positive for a novel variant (NDM-11). METHODS: blaNDM genes were investigated in E. coli by PCR and sequencing, and blaNDM variants were further characterised. The susceptibility pattern of novel blaNDM-11 towards different antimicrobials was compared with blaNDM-1 by cloning and expression in E. coli TOP10. RESULTS: A total of 33 carbapenem-resistant E. coli isolates were screened by PCR for the presence of blaNDM, of which 15 (45.5%) were positive. Sequencing of the PCR products revealed 10 isolates with NDM-1 and 5 isolates with NDM variants (one each of NDM-4, NDM-8 and NDM-11 and two NDM-5). Other resistance genes, including blaTEM-1, blaCTX-M-15, blaVIM, plasmid-encoded AmpC blaCMY-2 and 16S methyltransferases (rmtB and rmtC), were also associated with NDM variants in different combinations. The blaNDM variants were located on a transferable IncF-type plasmid of >100kb. Pulsed-field gel electrophoresis (PFGE) showed that all five E. coli isolates were unrelated, and multilocus sequence typing (MLST) revealed that they all belonged to ST131. Expression of the blaNDM-1 and blaNDM-11 genes in E. coli TOP10 showed no significant difference in MICs to various β-lactams, including carbapenems. CONCLUSIONS: This study underlines the spread of NDM variants with other antimicrobial resistance genes in E. coli in South India. It also describes a novel NDM variant (blaNDM-11) having an antimicrobial resistance pattern similar to blaNDM-1.