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=Volume 11 - 2021

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=Background
Increasing use of colistin has led to the world-wide emergence of mobile colistin resistant gene (mcr). The present study aimed to identify and characterise mcr and other drug-resistant genes in colistin resistant Klebsiella pneumoniae clinical isolates.
Methods
Twenty-two colistin resistant K. pneumoniae 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 mcr-1 positive isolates. S1-PFGE and Southern hybridisation were performed for localisation of mcr-1 and blaNDM.
Results
Nineteen colistin resistant K. pneumoniae harboured mcr-1 and 3 had mgrB disruption. All  isolates harboured blaOXA-48-type and ESBL genes; 8 strains (5 with mcr-1 and 3 with mgrB disruption) co-harboured blaNDM. Efflux pumps genes AcrAB and mdtK were detected in all 22 and tol-C in 21 isolates. Virulence-related genes entB and irp-1 were detected in all 22, mrkD in 20 and fimH-1 in 18 isolates; 11 isolates were strong biofilm producers. PFGE clustered mcr-1 positive isolates into 08 groups based on ≥ 90% similarity; MLST revealed diverse sequence types, predominant being ST-15 (n=04) and ST-16 (n=04). Both mcr-1 and blaNDM were localised on plasmid and chromosome; mcr-1 was present on IncFII type, and blaNDM on IncFIB and IncA/C type plasmids. 
Conclusions
Colistin resistance in K. pneumoniae was predominantly mediated by mcr-1. Co-existence of colistin, carbapenem and other drug-resistant genes along with efflux pumps indicates towards enormous genomic plasticity in K. pneumoniae with ability to emerge as super-spreader of drug-resistance.