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Analysis of the pathogenicity locus in Clostridium difficile strains
1Department of Internal Medicine, Division of Infectious and Immunologic Diseases, University of California, Davis Medical Center, Sacramento, CA 95817, USA. stcohen@ucdavis.edu
The Journal of Infectious Diseases
|February 11, 2000
Summary
The Clostridium difficile pathogenicity locus (PaLoc) is stable in toxin-producing strains and absent in non-toxigenic ones. However, some defective PaLoc strains can still cause disease, requiring further research.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Clostridium difficile toxins A and B (tcdA, tcdB) are encoded within a 19.6-kb pathogenicity locus (PaLoc).
- The PaLoc also contains genes tcdD, tcdE, and tcdC, crucial for toxin production and regulation.
Purpose of the Study:
- To investigate the stability and conservation of the C. difficile PaLoc in toxigenic and non-toxigenic strains.
- To determine if PaLoc integrity correlates with C. difficile-associated disease.
Main Methods:
- Multiplex polymerase chain reaction (PCR) was employed to analyze the PaLoc structure.
- Fifty toxigenic, 39 non-toxigenic, and 2 toxin-defective C. difficile isolates were examined.
Main Results:
- Toxigenic isolates consistently showed amplicons for tcdA-E, indicating PaLoc presence.
- Non-toxigenic isolates lacked the PaLoc genes.
- Specific isolates (P-829, 8864) exhibited deletions or missing fragments within the PaLoc genes, including tcdA and tcdC.
Conclusions:
- The C. difficile PaLoc is a highly stable genetic unit in toxigenic strains.
- Non-toxigenic strains are characterized by the absence of the PaLoc.
- Clinical disease can occur even with a defective PaLoc, highlighting the complexity of C. difficile pathogenesis.