Propagation of mcr-1 through Inc FIA in Escherichia coli ST5162 in a tertiary referral hospital of North-East India

Abstract

Colistin is regarded as the ultimate choice of antibiotic to use against gram-negative bacteria which are resistant to multiple antibiotics. The plasmid-mediated colistin resistance gene, mcr-1, which can transfer horizontally poses a notable risk to public health. Therefore, this study aimed at investigating the occurrence of mcr-1 harboring colistin-resistant Escherichia coli isolates in a tertiary referral hospital in the North-Eastern part of India. A total of 126 E. coli isolates were obtained from different wards of Silchar Medical College and Hospital during August 2018 to February 2019. Phenotypic resistance to colistin was determined by the broth microdilution method and polymyxin NP test. Genotypic characterization was done by PCR assay followed by sequencing. Co-occurrence of other resistance determinants was determined. Transferability was determined by transformation and conjugation assay. PCR- based plasmid incompatibility typing and Multilocus sequence typing (MLST) were performed. 29 E. coli isolates were screened positive for colistin resistance. The mcr-1 gene was found in two E. coli isolates belonging to sequence type ST5162. Co-occurrence of other antibiotic resistance genes namely aph(4)Ia, ant(2″)-Ia, aac(3)-I, aac(3)-IIc, sul1, and qepA were observed. The resistance determinants were found to be horizontally transferable and located within the IncFIA plasmid. This study revealed the propagation and adaptation of colistin resistance through IncFIA in a single clone of E. coli within a clinical setting which is of great concern for infection control and therapeutic choices. Therefore, urgent need for investigation is required to track down their source and continuance within hospital settings to minimize more lateral transfer.