Clostridium difficile isolates derived from Czech horses are resistant to enrofloxacin; cluster to clades 1 and 5 and ribotype 033 predominates.

This study conducted in the Czech Republic from 2015 to 2016 found that certain bacteria found in horse faeces were resistant to some antibiotics. The researchers examined 213 faecal samples from both hospitalised and non-hospitalised horses. It discovered that most of the antibiotic-resistant bacteria were found in hospitalised horses and identified seven different types of bacteria, most of which were susceptible to a variety of antibiotics, except one type, enrofloxacin.

Sampling and Bacterial Culturing

• From April 2015 to October 2016, 213 faecal samples were taken from both non-hospitalised (138 samples) and hospitalised horses (75 samples).
• Eighteen Clostridium difficile bacterial isolates were cultured from these faecal samples using a bacterial enrichment method. The majority of the bacteria, 16 samples, originated from hospitalised horses. This result was statistically significant (p < 0.01).

Types of Bacteria Identified

• Molecular typing of the bacteria revealed seven ribotypes and sequence types. The most common type was RT033/ST11, which made up 44.4% of the samples.
• The bacterial types identified were clustered into two clades, 1 and 5.

Antibiotic Resistance Observed

• All C. difficile bacteria isolated were susceptible to a variety of antibiotics including amoxicillin, metronidazole, moxifloxacin, and vancomycin.
• One type of bacteria (RT039) had a high level of resistance to antibiotics erythromycin and clindamycin. This type carried the ermB, adenine methylase gene, which may contribute to this resistance.
• Five other bacterial types were found to be resistant to clindamycin but not to erythromycin. These types did not carry the ermB gene.
• All bacterial isolates were resistant to the antibiotic enrofloxacin.
• Eight bacterial isolates were resistant to tetracycline. These isolates carried either the tetM gene or the tetW gene. Other mechanisms that can contribute to tetracycline resistance, namely tetA (P), tetB (P), and tetL were also identified in these samples. Co-occurrence of these genes lead to increased resistance to tetracycline.

Significance of Findings

Due to the detection of shared ribotypes between horses and humans, the study highlights the importance of monitoring the dissemination of antimicrobial resistance genes from veterinary healthcare to humans. This ‘One Health’ approach emphasises that health is interconnected across species and environments.