Genomic insights into a complete deletion of the mgrB locus in colistin-resistant Klebsiella pneumoniae ST2268 isolated from a human infection
Yunjia Song, Jinge Yang, Yingjiao Ju, Dejun Liu, Yang Wang, Xutao Sun, Yuan Lv
Abstract
OBJECTIVES: The emergence of colistin-resistant Klebsiella pneumoniae (CoRKp) is a serious public-health issue as colistin is the last line of defence against infections caused by multidrug-resistant Gram-negative bacteria. In this study, we generated a draft genome sequence for CoRKp strain P094-1 isolated from a sputum sample of an infected patient. METHODS: Whole genomic DNA of strain P094-1 was sequenced using a PacBio sequencing platform. Generated reads were de novo assembled using Hierarchical Genome Assembly Process (HGAP) v.3.0. Colistin resistance-related genes were predicted from the genome sequence and were validated experimentally. RESULTS: The genome of strain P094-1 lacked a 20.3-kb region, including complete deletion of the mgrB gene. Molecular and genome sequencing-based analyses revealed that the observed colistin resistance of P094-1 could not be attributed to plasmid-borne genes mcr-1 to mcr-9 or to alteration of the pmr and pho operons (deletions, insertions or substitutions), but was conferred by an insertion sequence 1 (IS1)-induced total deletion of mgrB. CONCLUSION: This is the first reported whole-genome sequence of an unusual CoRKp isolate containing an IS1-induced deletion of mgrB.