Tn6026 and Tn6029 are found in complex resistance regions mobilised by diverse plasmids and chromosomal islands in multiple antibiotic resistant Enterobacteriaceae

Abstract

Transposons flanked by direct copies of IS26 are important contributors to the evolution of multiple antibiotic resistance. Tn6029 and Tn6026 are examples of composite transposons that have become widely disseminated on small and large plasmids with different incompatibility markers in pathogenic and commensal Escherichia coli and various serovars of Salmonella enterica. Some of the plasmids that harbour these transposons also carry combinations of virulence genes. Recently, Tn6029 and Tn6026 and derivatives thereof have been found on chromosomal islands in both established and recently emerged pathogens. While Tn6029 and Tn6026 carry genes encoding resistance to older generation antibiotics, they also provide a scaffold for the introduction of genes encoding resistance to a wide variety of clinically relevant antibiotics that are mobilised by IS26. As a consequence, Tn6029 and Tn6026 or variants are likely to increasingly feature in complex resistance regions in multiple antibiotic resistant Enterobacteriaceae that threaten the health of humans and food production animals.

Complete Sequences of Multiple-Drug Resistant IncHI2 ST3 Plasmids in Escherichia coli of Porcine Origin in Australia

“…The insertion sequence IS26 of the IS6 family plays a significant role in the capture, assembly and mobilization of drug resistance genes found on plasmids (Dionisi et al, 2009;Cain et al, 2010;Shahid, 2010;Venturini et al, 2010Venturini et al, , 2013Lai et al, 2013;Abbo and Hooton, 2014;Chavda et al, 2015;Reid et al, 2015;Garcia et al, 2016) and in the chromosome (Roy Chowdhury et al, 2015. IS26 may promote plasmid stability and persistence by mediating deletions of plasmid backbone sequence, the expression of which incurs a burden to the host (Porse et al, 2016).…”

Drivers of antimicrobial resistance amongst intestinalEscherichia coliisolated from children in South Asia and sub-Saharan Africa

“…It is notable, however, that the pCERC-like plasmids (which often carried resistance to streptomycin, sulfonamides and trimethoprim), are very common in E. coli, possibly because their small size (~6 kbp, of which half encodes AMR genes) imposes a low fitness cost 32,44 . It is also notable that these and many of the other AMR genes we detected are also associated with composite transposons which can integrate into the bacterial chromosome, where they are maintained at lower fitness cost than large AMR plasmids 36,45,46 .…”

“…Common AMR-associated genes that were shown to be co-occurring, specifically bla , sul1, sul2, strA, strB, multiple dfrA alleles, tet(A) and tet(B), were further investigated in the aEPEC genome assemblies to determine if they were carried on the same mobile elements. The aEPEC genome assemblies generated previously using Velvet 51 were interrogated with BLAST, using as queries the AMR genes and the sequences of the plasmids pCERC1 (accession JN012467) and pCERC2 (accession KX291024), and the transposons Tn6029 (accession CG150541) 45 , Tn1721 (accession X61367) 67 and Tn10 (accession AF223162) 68 . For example, if the pCERC2 backbone and AMR genes were all detected on a single contig in the genome assembly, we inferred that these genes were moving together on a pCERC2-related plasmid.…”

Ecology and Evolution of the Human Microbiota: Fire, Farming and Antibiotics

“…This particularly applies to mobile DNA elements, whose presence can both expand the phylogenetic distribution of the parent element, and increase the number of possible interactions with other elements, thus generating enormous complexity through combinatorial assembly [ 61 ]. As a consequence, multi-resistance plasmids and other resistance loci have become home to an extraordinary array of insertion elements and transposons [ 62 , 63 , 64 ].…”