First hybrid complete genome ofAeromonas veroniireveals chromosome-mediated novel structural variantmcr-3.19from human clinical specimen

Abstract

BackgroundRecent findings substantiate the origin of plasmid-mediated colistin resistance gene mcr-3 from Aeromonads. The present study aimed to screen the plasmid-mediated colistin resistance among 30 clinical multidrug resistant (MDR) Aeromonas spp. ResultsThe presence of mcr-1, mcr-2, mcr-3, and mcr-4 were screened by PCR, which revealed mcr-3 in a colistin susceptible isolate (FC951). All other isolates were negative for mcr genes.Sequencing of FC951 revealed that mcr-3 (mcr-3.19) identified was different from previously reported variants and had 95.62 and 95.28% nucleotide similarity with mcr-3.3 and mcr-3.10 gene. A hybrid assembly using IonTorrent and MinION reads revealed structural genetic information of mcr-3.19 with an insertion of ISAs18 within the gene. Due to this, mcr-3.19was non-expressive which makes FC951 susceptible to colistin. Further, in silico sequence and protein structural analysis confirmed the new variant. To the best of our knowledge, this is the first report on novel mcr-3 variant (mcr-3.19). ConclusionsThe significant role of mcr-like genes in different Aeromonas species remains unknown and needs additional investigation to understand the insights on colistin resistance mechanism.