Characteristics of the Mare-Uterine-Culture-Based Bacterial Composition Using Practical Clinical Evaluation Methods

Uterine health is paramount to fertility in broodmares and for the success of a breeding project, and the Lusitano breed is no exception. This study aimed to characterize the mare uterine microbiota using practical clinical evaluation methods. Mares were examined by transrectal palpation and ultrasonography, followed by the collection of samples by one of three different techniques: uterine lavage, biopsy, or swab. The results of cytology, histology, microbiology, and antimicrobial susceptibility testing were recorded, and statistical analyses were performed. Inflammation was present in 42.2% of the mares and positive culture in 65.4%. <i>Escherichia coli</i> and <i>Streptococcus</i> spp. were the most isolated microorganisms. The most efficient antimicrobials were gentamicin, trimethoprim-sulfamethoxazole, and enrofloxacin and resistance was detected mainly for doxycycline, penicillin, and ceftiofur. The phase of the cycle was significantly associated with the presence of inflammation (<i>p</i> = 0.0308). The isolation of Gram-positive or Gram-negative bacteria correlated to the microbiological isolation by primoculture/enrichment processes (<i>p</i> = 0.0183). This was a routine standard breeding evaluation of broodmares in the management of a stud farm, hence displaying the characteristics of a field study. The antimicrobial resistance findings reinforce the importance of performing microbiology and susceptibility tests, even under field conditions, to maximize targeted antimicrobial therapy efficiency and minimize the worldwide problem of antimicrobial resistance, promoting antimicrobial stewardship.