The IS6 family, a clinically important group of insertion sequences including IS26

Abstract

The IS6 family of bacterial and archaeal insertion sequences, first identified in the early 1980s, has proved to be instrumental in the rearrangement and spread of multiple antibiotic resistance. Two IS, IS26 (found in many enterobacterial clinical isolates as components of both chromosome and plasmids) and IS257 (identified in the plasmids and chromosomes of gram-positive bacteria), have received particular attention for their clinical impact. Although few biochemical data are available concerning the transposition mechanism of these elements, genetic studies have provided some interesting observations suggesting that members of the family might transpose using an unexpected mechanism. In this review, we present an overview of the family, the distribution and phylogenetic relationships of its members, their impact on their host genomes and analyse available data concerning the particular transposition pathways they may use. We also provide a mechanistic model that explains the recent observations on one of the IS6 family transposition pathways: targeted cointegrate formation between replicons.

Whole Genome Sequencing of Extended-Spectrum- and AmpC- β-Lactamase-Positive Enterobacterales Isolated From Spinach Production in Gauteng Province, South Africa

“…Similar to the results of clinical K. pneumoniae strains reported by Mbelle et al (2020), In191, harbouring dfrA14 was identified in the three different K. pneumoniae sequence types of the current study, reiterating that it is not a narrow spectrum integron. In addition, dfrA14b was associated with IS6 that has previously been reported as having a vital role in the rearrangement and dissemination of antibiotic resistance (Varani et al, 2021). The presence of fosA and sul2 in all the K. pneumoniae strains of the current study also corresponds to the results reported by Mbelle et al (2020) from clinical K. pneumoniae strains in Pretoria.…”

IS 26 Is Responsible for the Evolution and Transmission of bla NDM -Harboring Plasmids in Escherichia coli of Poultry Origin in China

“…Furthermore, although in the absence of an active homologous recombination system, excision of TU was demonstrated in the context of Tn 4352B when it was adjacent to the two G residues at the left end of the IS 26 ; in other cases, this does not occur ( 29 ), and generation of a TU from a preexisting transposon would necessarily occur via homologous recombination ( 26 ). RecA-dependent simple homologous recombination from a IS 26 -based PCT could lead to excision for forming the TU ( 30 , 31 ). In our study, the absence of GG at the left end of the IS 26 and target site duplication (TDS) flanking IS 26 suggest that the circular intermediates were most likely generated from preexisting tandem arrays of IS 26 -associated modules on MRR via homologous recombination in the recA -carrying ( recA + ) E. coli strain J53.…”

Co-harboring of Novel blaKPC–2 Plasmid and Integrative and Conjugative Element Carrying Tn6203 in Multidrug-Resistant Pseudomonas aeruginosa

“…This TU might then have inserted into another plasmid. Normally, the integration results in two copies IS 26 in direct orientation, one at each boundary between the two participating molecules ( Harmer et al, 2014 ; Harmer and Hall, 2015 ; Varani et al, 2021 ). However, we observe only one IS 26 in pP33-2; the other might possibly have been lost through a deletion event.…”