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A New Composite Integrative and Conjugative Element Mediates Multiple Drug Resistance from Streptococcus anginosus to
Yingting Wang1, Taoran Liu1, Sida Yi2
1Department of Critical Care Medicine, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, 510080, People's Republic of China.
Introduction:
Integrative and conjugative elements (ICEs) are a category of horizontal mobile genetic elements (MGEs) that play important roles in mediating the spread of antimicrobial resistance in Streptococci.
Methods:
In this study, a novel ICE, namely ICESan26_rplL, was identified from commensal Streptococcus anginosus through routine silico analyses. The genetic characterization of ICESan26_rplL was explored based on a comparison with known ICEs. The cyclization and cross-species transferability (from Streptococcus anginosus to Streptococcus agalactiae) of ICESan26_rplL were explored using inverse PCR and conjugation transfer experiments.
Results:
ICESan26_rplL is 61.618 kb in length at downstream of rplL and carries multiple antibiotic resistance genes, including erm(B) [for erythromycin, clindamycin, and streptococcin B (MLSB)], tetM-tetL (tetracycline), lnu and lsa(E) (clindamycin), and ant(6)-I (aminoglycosides). The comparative analysis results showed that ICESan26_rplL was a composite ICE with a mosaic structure composed of modules in the ICESa2603 and TnGBS families. The inverse PCR results demonstrated that ICESan26_rplL could be excised from the chromosome to form a circular intermediate. The conjugation transfer experiment and sequencing results confirmed the cross-species transfer of ICESan26_rplL to S. agalactiae recipients at a relatively low frequency (2.13 × 10-8). Moreover, core functional modules were retrieved from GenBank to search for any ICEs related to ICESan26_rplL. Eventually, 53 putative ICEs were identified, including three composite ICEs with high similarity to ICESan26_rplL, three ICEs in the TnGBS family, and 47 ICEs in the ICESa2603 family.
Discussion:
In this study, a novel mosaic ICE was reported for the first time. In addition, its transfer to the major pathogen Streptococcus agalactiae was characterized and proved. These findings suggest that this ICE is expected to become a vehicle for the dissemination of multiple antimicrobial resistance through the wider pathogen Streptococci.
Insights
A novel integrative and conjugative element (ICE), ICESan26_rplL, carrying multiple antibiotic resistance genes was identified in Streptococcus anginosus. This ICE demonstrated transferability to Streptococcus agalactiae, highlighting its potential role in spreading antimicrobial resistance.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Integrative and conjugative elements (ICEs) are mobile genetic elements crucial for horizontal gene transfer.
- ICEs contribute significantly to the dissemination of antimicrobial resistance (AMR) in bacterial populations, particularly in Streptococci.
Purpose of the Study:
- To identify and characterize a novel ICE from commensal Streptococcus anginosus.
- To investigate the genetic structure, excision, and cross-species transferability of the novel ICE.
- To assess the potential of this ICE in mediating the spread of antibiotic resistance genes.
Main Methods:
- Bioinformatic analysis for ICE identification.
- Comparative genomics to characterize the ICE structure.
- Inverse PCR to confirm chromosomal excision and circularization.
- Conjugation experiments to assess interspecies transferability.
- Sequencing to verify successful transfer.
Main Results:
- A novel 61.6 kb ICE, ICESan26_rplL, was identified downstream of rplL in S. anginosus.
- ICESan26_rplL carries multiple antibiotic resistance genes, including erm(B), tetM-tetL, lnu, lsa(E), and ant(6)-I.
- The ICE demonstrated successful excision and cross-species transfer to Streptococcus agalactiae at a frequency of 2.13 × 10-8.
- Comparative analysis revealed a mosaic structure composed of modules from ICESa2603 and TnGBS families.
Conclusions:
- ICESan26_rplL represents a novel mosaic ICE with significant implications for AMR dissemination.
- The demonstrated transferability to the pathogen S. agalactiae underscores its potential as a vehicle for spreading multidrug resistance.
- This finding highlights the importance of monitoring ICEs in commensal bacteria for understanding and controlling AMR spread in Streptococci.
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