Antibiotic prophylaxis and hospitalization of horses subjected to median laparotomy: gut microbiota trajectories and abundance increase of Escherichia.

The research article investigates how peri-operative antibiotic prophylaxis impacts the gut microbiota of horses undergoing median laparotomy, a common surgical procedure for treating acute colic. The research also documents an increase in multidrug-resistant bacteria following the procedure.

Research Methodology

• The researchers collected fecal samples from two groups of horses receiving different peri-operative antibiotic prophylaxis (PAP) treatment plans: one group received a single pre-surgical dose while the other received a 5-day course of the treatment. A third control group made up of non-hospitalized horses was also monitored.
• These samples were collected at hospital admission and on days three and ten post-surgery, then tested for the presence of ESBL-producing Enterobacterales, a multidrug-resistant bacterium, and subjected to 16S rRNA V1-V2 gene sequencing to identify the bacterial species present.
• A total of 48 samples from the single shot group (SSG), 45 from the 5-day group (5DG), and 20 from the control group (CG) were included in the study.

Findings

• The results indicated that at the time of surgery, 6.5% of samples from horses receiving PAP treatment were positive for ESBL-producing Enterobacterales. This rate dramatically increased to 67% by day three post-surgery and stayed relatively unchanged at day ten.
• The study utilized the Shannon Diversity Index (SDI) to evaluate the diversity of bacterial life within the gut microbiomes of the horses. Initial results did not find a significant variance in the bacteria diversity in the acute colic-affected horses compared to the control group.
• However, SDI significantly decreased in both PAP groups by day three and only began to recover by day ten. Although no significant variance in SDI with respect to PAP duration was found, community structure was notably limited in the 5-day group samples, likely due to the extended antibiotic administration.
• A higher abundance of Escherichia, specifically an ESBL-producing Enterobacterales bacteria, was found in the samples from the two experimental groups.

Conclusion

• The study concludes that colic surgery in conjunction with PAP promotes dysbiosis (a microbial imbalance) in the equine gut, leading to a reduction in microbiome diversity and an increase in multidrug-resistant bacteria.
• More research is necessary to understand the factors that promote the multiplication and persistence of ESBL-producing Enterobacterales among hospitalized horses in order to develop strategies for controlling its spread.