NEW INSIGHTS INTO THE DIAGNOSIS AND TREATMENT OF ENDOMETRITIS IN THE MARE

The first part of this thesis focused on microbiome. A first experiment on healthy mares was performed and the uterine microbiome of 11 mares was characterized using the 16S rRNA sequencing technique. The most abundant genera were Staphylococcus, Acinetobacter, Sphingomonas, Corynebacterium, Streptococcus, Rikenellaceae, Clostridium, Pseudomonas and Porphyromonas. Furthermore, this experiment investigated the differences between estrus and diestrus and showed that during diestrus, diversity is reduced probably due to hormonal fluctuations and the closed cervix, which does not allow the ascension of bacteria from the vagina. In addition, the uterine microbiome of 5 mares with endometritis was described for the first time in the second experiment. The microbiome was dominated by the genera Streptococcus and Escherichia Shigella, confirming the results of the culture technique. Furthermore, Corynebacterium accounted for most of the relative abundance in one of the mares. After treatment with ceftiofur sodium, a drastic decrease in the relative abundance of pathogenic bacterial genera and the restoration of a more diverse environment was observed. Thus, we were able to demonstrate that bacterial genera commonly considered pathogenic are normal components of the uterine microbiota of healthy mares. In mares with endometritis, however, they are overrepresented and dominate the endometrial microbiome, which is in a state of dysbiosis characterized by a reduction in bacterial diversity. Intrauterine antibiotic treatment led to the restoration of a more diverse microbiome. The second part of this thesis deals with a promising treatment for endometritis, ozone therapy. In the first study, the safety and effects of a commercial product based on ozonated oil, Riger Spray® were evaluated. Cytological, bacteriological and histological examinations before and after treatment revealed a temporary increase in inflammation of the endometrium, but the product proved to be safe. In addition, it did not have a negative effect on pregnancy rates, but a tendency towards a lower number of inseminations required to achieve pregnancy in the treatment group was observed. In the second study, the antibacterial effect of various ozone preparations on antibiotic-resistant intrauterine pathogens in vitro was evaluated. Ozonized oil, gaseous ozone in two different concentrations and three exposure times as well as ozonized water were tested. In the present study, ozonated distilled water showed no significant antibacterial effect. On the other hand, both gaseous ozone and ozonated oil showed antimicrobial activity against antibiotic-resistant bacterial and yeast strains responsible for endometritis. Moreover, even lower concentrations of gaseous ozone than previously reported showed efficacy in vitro. Thus, ozone therapy proved to be a promising treatment for infectious endometritis, and these results provide a solid scientific rationale for its use in vivo as an antimicrobial agent to reduce the over-use of antibiotics in equine reproduction. The last part of this thesis is based on the question of whether a clinical sign associated with endometritis, namely intrauterine fluid accumulation (IUF), can affect the results of a commercial ET program. We have distinguished two phases for the observation of IUF: pre-ovulation (estrus) and post-ovulation (early diestrus). Fluid during estrus is considered physiological in the literature when the depth is <2cm, and the results of this study confirmed this hypothesis as it did not affect the success of the transfer. On the other hand, fluid during the diestrus phase is associated with uterine inflammation and/or delayed uterine clearance. Our retrospective study described a negative impact of post-ovulation IUF detection on transfer success. This seems to confirm the link between IUF in the diestrus phase and endometritis/delayed clearance and suggests that these mares should be avoided as embryo recipients.