AUTHOR=Singh Sanjay , Pathak Ashutosh , Rahman Mohibur , Singh Avinash , Nag Soumyabrata , Sahu Chinmoy , Prasad Kashi Nath 

TITLE=Genetic Characterisation of Colistin Resistant Klebsiella pneumoniae Clinical Isolates From North India

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.666030

DOI=10.3389/fcimb.2021.666030

ISSN=2235-2988

ABSTRACT=<sec><title>Background</title><p>Increasing use of colistin has led to the world-wide emergence of mobile colistin resistant gene (<italic>mcr</italic>). The present study aimed to identify and characterise mcr and other drug-resistant genes in colistin resistant <italic>Klebsiella pneumoniae</italic> clinical isolates.</p></sec><sec><title>Methods</title><p>Twenty-two colistin resistant <italic>K. pneumoniae</italic> were analysed for mcr and other drug-resistant genes, efflux pumps, and virulence genes, and for their biofilm forming ability. Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) were performed for all <italic>mcr-1</italic> positive isolates. S1-PFGE and Southern hybridisation were performed for localisation of <italic>mcr-1</italic> and <italic>bla</italic><sub>NDM</sub>.</p></sec><sec><title>Results</title><p>Nineteen colistin resistant <italic>K. pneumoniae</italic> harboured <italic>mcr-1</italic> and 3 had <italic>mgrB</italic> disruption. All isolates harboured <italic>bla</italic><sub>OXA-48</sub>-type and ESBL genes; eight strains (five with <italic>mcr-1</italic> and three with <italic>mgrB</italic> disruption) co-harboured <italic>bla</italic><sub>NDM</sub>. Efflux pumps genes <italic>AcrAB</italic> and <italic>mdtK</italic> were detected in all 22 and <italic>tol-C</italic> in 21 isolates. Virulence-related genes entB and <italic>irp-1</italic> were detected in all 22, <italic>mrkD</italic> in 20, and <italic>fimH-1</italic> in 18 isolates; 11 isolates were strong biofilm producers. PFGE clustered <italic>mcr-1</italic> positive isolates into eight groups based on ≥90% similarity; MLST revealed diverse sequence types, predominant being ST-15 (n = 4) and ST-16 (n = 4). Both <italic>mcr-1</italic> and <italic>bla</italic><sub>NDM</sub> were localised on plasmid and chromosome; <italic>mcr-1</italic> was present on IncFII type and <italic>bla</italic><sub>NDM</sub> on IncFIB and IncA/C type plasmids.</p></sec><sec><title>Conclusions</title><p>Colistin resistance in <italic>K. pneumoniae</italic> was predominantly mediated by <italic>mcr-1</italic>. Co-existence of colistin, carbapenem, and other drug-resistant genes along with efflux pumps indicates towards enormous genomic plasticity in <italic>K. pneumoniae</italic> with ability to emerge as super-spreader of drug-resistance.</p></sec>