Lipid A-Ara4N as an alternate pathway for (colistin) resistance in Klebsiella pneumonia isolates in Pakistan

Abstract

Objectives This study aimed to explore mechanism of colistin resistance amongst Klebsiella pneumoniae isolates through plasmid mediated mcr-1 gene in Pakistan. Carbapenem and Colistin resistant K. pneumoniae isolates (n = 34) stored at − 80 °C as part of the Aga Khan University Clinical Laboratory strain bank were randomly selected and subjected to mcr-1 gene PCR. To investigate mechanisms of resistance, other than plasmid mediated mcr-1 gene, whole genome sequencing was performed on 8 clinical isolates, including 6 with colistin resistance (MIC > 4 μg/ml) and 2 with intermediate resistance to colistin (MIC > 2 μg/ml). Results RT-PCR conducted revealed absence of mcr-1 gene in all isolates tested. Whole genome sequencing results revealed modifications in Lipid A-Ara4N pathway. Modifications in Lipid A-Ara4N pathway were detected in ArnA_ DH/FT, UgdH, ArnC and ArnT genes. Mutation in ArnA_ DH/FT gene were detected in S3, S5, S6 and S7 isolates. UgdH gene modifications were found in all isolates except S3, mutations in ArnC were present in all except S1, S2 and S8 and ArnT were detected in all except S4 and S7. In the absence of known mutations linked with colistin resistance, lipid pathway modifications may possibly explain the phenotype resistance to colistin, but this needs further exploration.

Determination of Mutational Timing of Colistin-Resistance Genes through Klebsiella pneumoniae Evolution

“…Colistin resistance has been extensively studied with meaningful mutations and their roles in the resistance mechanism identified. Modifications in lipid A moiety of LPS, overexpression of two-component regulatory systems PhoPQ and PmrAB, plasmid-mediated transfer of mobilized colistin resistance genes mcr-1 to mcr-8 , and the inactivation of the PhoQ/PhoP signaling regulator MgrB are some of the most understood mechanisms of colistin resistance in Gram-negative bacteria [ 14 , 37 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. In this study, we narrow the knowledge gap in understanding the importance of mutation timing in the progression of COL-R by gene function for both planktonic and biofilm KP lifestyles.…”