Longitudinal study of Clostridium difficile and antimicrobial susceptibility of Escherichia coli in healthy horses in a community setting.

This study investigates the presence, evolution, and antibiotic resistance of certain pathogenic bacteria in healthy horses over a one-year period. The researchers found shifting patterns of Clostridium difficile types, no Clostridium perfringens or Salmonella, and low levels of antibiotic resistance in Escherichia coli.

Research Objectives

The research had several main objectives:

• To longitudinally examine the presence and types of three enteric pathogens: Clostridium difficile, Clostridium perfringens and Salmonella in healthy horses over a one-year period.
• To molecularly characterize any isolates of these bacteria to understand any inter- or intra-species variations.
• To determine the antibiotic resistance profile of Escherichia coli in the horses, as this species is often used as a baseline to evaluate antimicrobial resistance of gut bacteria.

Methodology

The approach involved:

• Collecting fecal samples from 25 adult horses monthly for a year.
• Performing selective cultures for the mentioned bacteria.
• Characterizing any C.difficile found via PCR toxin gene profiling and ribotyping.
• Assessing antimicrobial susceptibility profiles of E.coli using broth microdilution.

Key Findings

The key findings include:

• Toxigenic Clostridium difficile was found in 5.45% of samples and 40% of the horses.
• Four horses carried the bacteria at multiple times, but three had different types (or “ribotypes”) which indicates that the bacterial profile can change within individual horses over time.
• The ribotypes identified were 078 (most common), 001, and C. This may reflect a recent upsurge of ribotype 078 in the local horse population.
• Neither Clostridium perfringens nor Salmonella were found in any of the samples.
• Escherichia coli was isolated from 77% of fecal samples. Antibiotic resistance to at least one type of drug was found in 13.4% of these, and to three or more types in 2.6%.

The results suggest that healthy horses may not be significant carriers of antibiotic resistance in gut bacteria. The fluctuating presence of different ribotypes in C.difficile in individual horses indicates that carriage of these bacteria is likely transient within this population.