Real-time PCR and typing of Clostridium difficile isolates colonizing mare-foal pairs.

This study investigated whether the bacterium Clostridium difficile, which can cause inflammation of the gut and diarrhea, can be colonized from mares (female horses) to their foals. By using real-time PCR and typing methods, the study found that 36.4% of the mare-foal pairs studied carried the same strains of C. difficile, suggesting possible cross-colonization.

Sampling and identification of Clostridium difficile

• The study collected fecal samples from 11 pairs of mares and their foals. Of those, two mares and three foals had diarrhea, a common symptom of Clostridium difficile infection.
• Fecal immunoassays, tests that detect antigens or antibodies in stool samples, were used to detect the presence of C. difficile and one of its toxins, toxin A.
• Isolates of C. difficile from these samples were then identified and genotyped. Genotyping is a process that determines the genetic information of an organism by examining their DNA sequences. In this case, it helped to identify unique strains of C. difficile.

Quantitative real-time PCR (qPCR)

• The study also used a process called quantitative real-time PCR (qPCR). This is a laboratory technique that allows scientists to see how much of a specific DNA sequence is present in a sample. The qPCR systems in this study were looking for the presence of genes for toxins A and B, as well as binary toxin B.
• While all the C. difficile isolates were found to have the sequence of all toxins, only one horse was found positive for toxin A through the fecal immunoassay.

Results and Implications

• The key finding was that identical strains of C. difficile were present in 4 out of the 11 mare-foal pairs. This indicates that the same strain of C. difficile can infect both mares and their foals, suggesting the possibility of cross-colonization.
• Given that C. difficile infections can be serious and potentially life-threatening, the study’s findings underscore the potential risk that mare-foal pairs could pose in terms of mutually infecting each other with C. difficile. Thus, the study calls for more careful monitoring of mare-foal pairs, especially those exhibiting symptoms of diarrhea.
• Notably, the mare-foal pairs were able to harbor C. difficile subclinically—that is, even when no signs of disease were visible. This makes proactive screenings and testing of mares and foals all the more necessary to prevent the spread of C. difficile.