[Clostridium difficile, nosocomial enteropathogen: phylogeny and virulence].

Area of Science:

• Microbiology
• Genetics
• Epidemiology

Background:

• Clostridium difficile is a nosocomial enteric pathogen causing diarrhea and pseudomembranous colitis.
• Pathogenesis involves altered digestive flora due to antibiotic treatment, allowing toxin-producing strain colonization.
• Strains can produce toxin A (enterotoxin) and toxin B (cytotoxin), with variations in toxin profiles (A+B+, A-B+).

Purpose of the Study:

• To investigate the phylogenetic relationships of Clostridium difficile strains.
• To develop and apply MultiLocus Sequence Typing (MLST) for detailed phylogenetic analysis.
• To correlate phylogenetic lineages with host association, disease presentation, and toxin production.

Main Methods:

• Development of MultiLocus Sequence Typing (MLST) analysis for C. difficile.
• DNA sequencing of housekeeping genes to identify allelic polymorphisms.
• Phylogenetic analysis of sequence data to determine evolutionary relationships.

Main Results:

• C. difficile exhibits genomic stability with evidence of mutational clonal evolution and distinct phylogenetic lineages.
• Identified lineages are not correlated with human or animal hosts.
• Strains causing diarrhea or pseudomembranous colitis do not form distinct phylogenetic lineages.
• Bi-toxinogenic (A+B+) and non-toxinogenic strains do not segregate into separate lineages.
• A-B+ toxin-producing strains represent a unique, highly divergent clone.

Conclusions:

• MLST provides a robust method for analyzing C. difficile phylogeny and macro-epidemiology.
• Phylogenetic analysis reveals distinct evolutionary trajectories within C. difficile, including a unique A-B+ clone.
• The findings challenge simple correlations between host, disease, and toxin profile, highlighting genomic divergence as a key factor.