Targeted IS-element sequencing uncovers transposition dynamics during selective pressure in enterococci

• Published in: PLoS pathogens 2023-06, Vol.19 (6), p.e1011424
• Main Authors: Kirsch, Joshua M, Ely, Shannon, Stellfox, Madison E, Hullahalli, Karthik, Luong, Phat, Palmer, Kelli L, Van Tyne, Daria, Duerkop, Breck A
• Format: Article
• Language: English
• Subjects: Adaptation; Analysis; Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Antibiotics; Bacteria; Biology and Life Sciences; Chronic infection; Diversification; DNA Transposable Elements - genetics; Dosage and administration; Drug resistance; Drug resistance in microorganisms; Drug Resistance, Microbial; Enterococcal infections; Enterococcus - genetics; Enterococcus faecalis - genetics; Enterococcus faecium; Evolution; Evolutionary biology; Genes; Genetic transcription; Genomes; Genomics; Gram-positive bacteria; Health aspects; Health risks; Humans; Inactivation; Infection; Insertion sequences; Medicine and Health Sciences; Nosocomial infection; Nosocomial infections; Phages; Phylogenetics; Plasmids; Prevention; Recombination; Risk factors; Transposase; Transposase gene; Transposition; Transposons; Virulence; Virulence (Microbiology)
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1011424

Insertion sequences (IS) are simple transposons implicated in the genome evolution of diverse pathogenic bacterial species. Enterococci have emerged as important human intestinal pathogens with newly adapted virulence potential and antibiotic resistance. These genetic features arose in tandem with large-scale genome evolution mediated by mobile elements. Pathoadaptation in enterococci is thought to be mediated in part by the IS element IS256 through gene inactivation and recombination events. However, the regulation of IS256 and the mechanisms controlling its activation are not well understood. Here, we adapt an IS256-specfic deep sequencing method to describe how chronic lytic phage infection drives widespread diversification of IS256 in E. faecalis and how antibiotic exposure is associated with IS256 diversification in E. faecium during a clinical human infection. We show through comparative genomics that IS256 is primarily found in hospital-adapted enterococcal isolates. Analyses of IS256 transposase gene levels reveal that IS256 mobility is regulated at the transcriptional level by multiple mechanisms in E. faecalis, indicating tight control of IS256 activation in the absence of selective pressure. Our findings reveal that stressors such as phages and antibiotic exposure drives rapid genome-scale transposition in the enterococci. IS256 diversification can therefore explain how selective pressures mediate evolution of the enterococcal genome, ultimately leading to the emergence of dominant nosocomial lineages that threaten human health.