# IME_Rho_tet, a novel family of putative integrative mobilizable elements spreading tetracycline resistance genes tet(W) and tet(32) among human and animal gut bacteria

## TL;DR

A new genetic element called IME_Rho_tet is found to spread tetracycline resistance genes in gut bacteria from humans and animals.

## Contribution

Identification of IME_Rho_tet as a novel integrative mobilizable element spreading tet(W) and tet(32) resistance genes.

## Key findings

- IME_Rho_tet elements were detected in 504 complete and 1,090 partial forms, with 68% encoding Tet(W).
- 71% of tet(W) and 87% of tet(32) in gut bacteria are linked to IME_Rho_tet.
- IME_Rho_tet was found in over 60 Bacillota and 20 Actinomycetota genera, showing broad host range.

## Abstract

Antimicrobial resistance remains a major global health concern in human and animal medicine. Tetracycline resistance genes of the ribosomal protection protein (RPP) family, especially tet(W), are among the most abundant resistance genes in livestock animals and human gut microbiota. However, genetic determinants responsible for the spread of tet(W) are not yet fully described. Here, all genomes of the phyla Bacillota and Actinomycetota available in RefSeq were screened for Tet(W)-related proteins as well as signature proteins of a new putative integrative mobilizable element (IME) recently described to carry the tet(W) gene. This element, hereafter named IME_Rho_tet, showed an extensive diversity, both for its relaxase and serine recombinase signature proteins and for the encoded tetracycline resistance protein. A total of 504 complete and 1,090 partial IME_Rho_tet elements were detected, of which 68% encoded Tet(W). The remaining IME_Rho_tet encoded other RPPs, including Tet(32), Tet(O) and the mosaic Tet(O/32/O), as well as a few novel RPP and variants. Overall, 71% of all tet(W) detected in bacteria isolated from human or animal gut were linked to IME_Rho_tet, as well as 87% of all tet(32). IME_Rho_tet elements showed an extensive bacterial host range, as complete elements were detected in more than 60 Bacillota genera, while partial elements were also detected in 20 Actinomycetota genera. Finally, eight of the ten mobile elements reported in the literature as carrying tet(W) or tet(32) included complete or partial IME_Rho_tet. These findings highlight the IME_Rho_tet family as a key genetic player in the dissemination of tet(W) and tet(32) among gut-associated bacteria of humans and food-producing animals.