Integrative and conjugative elements in streptococci can act as vectors for plasmids and translocatable units integrated via IS 1216E

Mobile genetic elements (MGEs), such as integrative and conjugative elements (ICEs), plasmids and translocatable units (TUs), are important drivers for the spread of antibiotic resistance. Although ICEs have been reported to support the spread of plasmids among different bacteria, their role in mobilizing resistance plasmids and TUs has not yet been fully explored. In this study, a novel TU bearing optrA, a novel non-conjugative plasmid p5303-cfrD carrying cfr(D) and a new member of the ICESa2603 fam-ily, ICESg5301 were identified in streptococci. Polymerase chain reaction (PCR) assays revealed that three different types of cointegrates can be formed by IS1216E-mediated cointegration between the three differ-ent MGEs, including ICESg5301::p5303-cfrD::TU, ICESg5301::p5303-cfrD, and ICESg5301::TU. Conjugation assays showed that ICEs carrying p5303-cfrD and/or TU successfully transferred into recipient strains, thereby confirming that ICEs can serve as vectors for other non-conjugative MGEs, such as TUs and p5303-cfrD. As neither the TU nor plasmid p5303-cfrD can spread on their own between different bacte-ria, their integration into an ICE via IS1216E-mediated cointegrate formation not only increases the plas-ticity of ICEs, but also furthers the dissemination of plasmids and TUs carrying oxazolidinone resistance genes.(c) 2023 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.

Automated summary

This study identified a novel integrative and conjugative element (ICE) that can mobilize resistance plasmids and translocatable units (TUs), contributing to the spread of antibiotic resistance. The formation of different cointegrates between ICEs, plasmids, and TUs was confirmed through PCR assays. Conjugation assays showed that ICEs can transfer non-conjugative MGEs, such as TUs and plasmids, into recipient strains.