Molecular characterization of Clostridium difficile isolates from horses in an intensive care unit and association of disease severity with strain type.

The research investigates the molecular characteristics, antimicrobial resistance, and toxin production of Clostridium difficile bacteria in horses, emphasizing on the association between disease severity and specific strains. The study reveals that the type of C. difficile strain can significantly influence the severity of the disease, with metronidazole-resistant strains possibly linked to severe disease conditions.

Methodology

The researchers carried out a prospective study on 130 horses admitted to an intensive care unit for acute gastrointestinal disease with loose feces. The following mechanisms were employed:

• Fecal samples were taken from the horses for microbial culture to understand the bacterial make-up and for immunoassay to evaluate toxin production.
• Genomic study of the isolates was performed using polymerase chain reaction assays. This helped in identifying the presence of toxins A and B genes and also in strain identification.

Findings

Based on the molecular banding patterns, the isolates were categorized into three strains: A, B, and C. The main findings include:

• Both toxins A and B gene sequences were identified in 93% and 73% of isolates of strains A and C respectively, and in 95% of strain B isolates.
• Results of the fecal immunoassays showed that toxin A was present in 40%, 63%, and 16% of horses with strains A, B, and C, respectively.
• Strain B isolates were resistant to the antibiotic metronidazole, and horses infected with this strain were ten times more likely to have been treated with metronidazole prior to displaying signs of diarrhea than those infected with other strains.
• The study revealed that horses infected with strain B had a longer recovery period, greater systemic inflammatory response, and a higher mortality rate than those infected with strains A and C.

Conclusion

The research concludes that horses can be infected by a variety of C.difficile strains. There was significant variation in the toxigenicity and antimicrobial resistance of the isolates. Of particular concern was the strain B which showed resistance to metronidazole and seemed to be associated with severe disease. Therefore, understanding the molecular characteristics of these strains is essential for the effective treatment and management of the disease.