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Identification of large cryptic plasmids in Clostridioides (Clostridium) difficile
Jacob Amy1, Dieter Bulach2, Daniel Knight3
1Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, VIC 3800, Australia.
Plasmid
|April 28, 2018
Summary
Large plasmids were found in nearly 5% of Clostridioides difficile isolates. These plasmids, resembling bacteriophages, lack known virulence factors, prompting further research into their maintenance.
Area of Science:
- Microbiology
- Bacterial genetics
- Plasmid biology
Background:
- Clostridioides difficile is a significant human and animal pathogen.
- Pathogenic clostridia often possess large plasmids encoding virulence, antibiotic resistance, and metabolic genes.
- Previous studies identified small cryptic plasmids in C. difficile, but recent plasmid prevalence and diversity remain underexplored.
Purpose of the Study:
- To investigate the prevalence and characteristics of plasmids in Clostridioides difficile isolates.
- To identify potential genetic elements and origins of newly discovered large plasmids in C. difficile.
Main Methods:
- Survey of clinical and historical C. difficile isolates.
- Whole-genome sequencing of strains carrying large plasmids.
- Bioinformatic analysis to characterize plasmid structure and identify genetic features.
Main Results:
- Large plasmids (42-47 kb) with high nucleotide identity were identified in 4.9% of surveyed C. difficile isolates.
- These plasmids showed no strong association with specific strain backgrounds.
- Plasmids exhibited characteristics of both bacteriophages (recombination) and plasmids (replication/partitioning loci), but lacked identified virulence or antibiotic resistance genes.
Conclusions:
- A novel type of large plasmid is present in a subset of Clostridioides difficile isolates.
- The origin of these plasmids appears to involve bacteriophage recombination.
- The selective advantage conferred by these plasmids to their host bacteria remains to be elucidated.
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