F2F Poster 21st Lancefield International Symposium for Streptococci and Streptococcal Diseases 2022

A new integrative and mobilizable element is the major contributor to tetracycline resistance in Streptococcus dysgalactiae subsp equisimilis (#309)

Guillem López de Egea Vegas 1 , Aida González 1 , Gérard Guedon 2 , Julie Lao 2 , Dàmaris Berbel 1 , Antonio Casabella 3 , Jose Maria Marimón 4 , Emilia Cercenado 5 , M. Ángeles Domínguez 1 , Nathalie Leblond 2 , Carmen Ardanuy 1
  1. Microbiology, Hospital Universitari de Bellvitge-IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
  2. Université de Lorraine, INRAE DynAMic, Nancy, France
  3. Microbiology, Hospital Universitari Parc Taulí, Sabadell, Barcelona, Spain
  4. Biodonostia, Infectious diseases area, Respiratory infection and antimicrobial resistance group, Osakidetza Basque health
  5. Clinical Microbiology and Infectious Disease Department, Hospital General Universitario Gregorio Marañón, Madrid, Spain

Background:

Tetracycline resistance (TET-R) in streptococci is mainly due to ribosomal protection mediated by tetM gene that is usually located into transposons of the Tn916 family.

This study aimed to analyse the genes involved in TET-R and the mobile genetic elements (MGEs) carrying them in Streptococcus dysgalactiae subsp equisimilis (SDSE) causing invasive disease.

Methods:

TET-R invasive SDSE (2012-2019 period) were analyzed by whole genome sequencing (WGS). Sequences were assembled using INNUCA. Thereafter, genomes were false-closed with CONTIGuator and annotated by RAST. Genes related to MGEs were annotated with ICEscreen (programme under development by the Université de Lorraine). Resistance genes were found using the ResFinder database.

Results:

Among 84 SDSE isolates, 25 (29.8%) were TET-R. Resistance was related to tetM (n=22), tetW (n=2), tetO (n=1) and/or tetL (n=1) genes. The tetM genes were found in transposons of the Tn916 family (n=10) and into a new integrative and mobilizable element (IME; n=12). This IME is composed of a tyrosine integrase and a relaxase of the MOBT family, with an undefined insertion site, and showed more than 95% homology with Enterococcus faecium and Clostridioides difficile genomes. The remaining TET-R genes (tetW, tetO, and tetL) were found in IMEs that were inserted into integrative and conjugative element genes, previously described.

Conclusions:

Tetracycline resistance in SDSE is mostly due to the tetM gene associated with two different elements: the Tn916 transposon and a new IME. This new IME is the most frequent cause of tetracycline resistance in invasive Streptococcus dysgalactiae subsp equisimilis.