Retrospective study of bacterial isolates and their antimicrobial susceptibilities in equine uteri during fertility problems

Fertility problems of mares on a well-managed breeding farm with thoroughbred stallions have been ascribed mostly to contamination of the reproductive apparatus of females with pathogens, particularly those of bacterial origin. This study presents a summary of the frequency of bacterial pathogens isolated from 437 cervical swabs which were collected from English thoroughbred mares intended for mating between 2008–2014, as well as of resistance tests of these pathogens to seven commonly used antibiotics as follows: penicillin, gentamicin, tetracycline, sulfisoxazole, cefotaxime, marbofloxacin and enrofloxacin. In addition, the study reports the changes in the levels of plasma oestradiol and progesterone determined two to three days before and two to three days after the first postpartum ovulation in mares with positive and dubious bacteriological findings and percentage of barren mares and mares that conceived at first, second and third post-partum ovulations. It was observed that 21.5% of mares were barren even after the third post-partum cycles. The oestradiol levels determined two to three days before the first post-partum ovulation were significantly lower in mares positive for pathogenic microflora in their reproductive apparatus compared to mares with the dubious findings (25.1 ± 5.8 pg/ml vs. 69.7 ± 18.3 pg/ml; P < 0.05), while the mean progesterone levels did not differ significantly but displayed a rather wide range in positive mares (from 0.08 to 1.38 ng/ml) compared to dubious mares with only small variations (0.12 ± 0.03 ng/ml). Moreover, of the total number of cervical swabs taken shortly before the first post-partum oestrus from all the mares intended for mating as many as 69.7% were contaminated with pathogenic microflora (positive findings). Saprophytic microorganisms only (the dubious findings) were isolated from 29.7% of swabs. From the 307 positive swabs, we could identify 40.4% positive for β-haemolytic streptococci and 20.4% positive for Escherichia coli, the pathogens implicated in causing reproductive disorders. Tests of antibiotic resistance of the investigated pathogens revealed that both Gram-positive and Gram-negative bacteria showed high susceptibility to antibiotics such as cefotaxime, marbofloxacin and enrofloxacin. On the other hand, both these bacterial groups showed high resistance to routinely used broad-spectrum antibiotics, such as penicillin and tetracycline. Because further research is required for a full understanding of the mechanism of pathogenesis of post-breeding endometritis, we can only hypothesise that uterine contamination with pathogenic microflora, particularly with β-haemolytic streptococci and coliform bacteria, diagnosed before the first post-partum ovulation, could negatively affect the hormonal regulation of oestrus and result in mare fertility problems.

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Incidence of bacterial pathogens in equine uterine swabs, their antibiotic resistance patterns, and selected reproductive indices in English thoroughbred mares during the foal heat cycle

This study aimed to describe bacteria isolated from the reproductive tract of mares and to identify changes in antimicrobial susceptibility patterns to those antibiotics commonly used for the treatment of equine endometritis. A total of 4122 equine uterine swabs were collected from mares suffering from reproductive tract disorders in the period 2010-2017. Aerobic culture and antimicrobial susceptibility testing using agar disc diffusion were performed on each sample. Aerobic bacteria were isolated from 3171 of 4122 (76.9 per cent) samples. The most frequently isolated microorganisms were Escherichia coli (885/3171, 27.9 per cent) and Streptococcus equi subspecies zooepidemicus (791/3171, 24.9 per cent), confirming previous findings from the literature. Antimicrobial susceptibility patterns of E coli, S equi subspecies zooepidemicus and Klebsiella pneumoniae changed over time. A statistically significant decrease in antimicrobial efficacy of cefquinome against E coli was observed over the years, as well as of ampicillin, cefquinome and penicillin against S equi subspecies zooepidemicus The high frequency of resistant bacteria isolated in the present work proceeds in the same way as indicated by surveillance data on the huge antibiotic use in Italy. As a result, testing and monitoring programmes of antimicrobial efficacy are crucial to consciously using antibiotics and preserving their effectiveness both for veterinary and human medicine.

Temporal efficacy of antimicrobials against aerobic bacteria isolated from equine endometritis: an Italian retrospective analysis (2010-2017)

In six healthy mares and 24 mares showing reproductive disorders swab samples were taken from the fossa clitoridis to isolate Taylorella equigenitalis, and from the uterus to isolate mycoplasmas, ureaplasmas and other aerobic bacteria. Swab samples were also taken from the uterus for Chlamydiaantigen ELISA and ChlamydiaPCR studies. The uterus of 27 mares was examined cytologically, and biopsy samples were taken from the endometrium for histological examinations and for immunohistochemical examinations aimed at the detection of chlamydiae. T. equigenitalis, mycoplasmas, ureaplasmas and chlamydiae could not be detected from any of the mares examined. Aerobic facultative pathogenic bacteria were isolated from mares with endometritis in four cases. In 18 out of 22 mares with endometritis (82%) no infective agents could be demonstrated. Further studies are needed to elucidate the relative importance of non-infectious causes of endometritis and of anaerobic bacteria often detectable in the uterus in the aetiolo...

Study of the role of Chlamydia, Mycoplasma, Ureaplasma and other microaerophilic and aerobic bacteria in uterine infections of mares with reproductive disorders.

Intestinal microbiota and the pathogenesis of dysbacteriosis in broiler chickens

Summary

A total of seven Bacteroides ureolyticus strains were isolated from the cervix and the clitoral fossa of mares with vaginal discharge. No other bacteria capable of causing metritis or vaginitis were isolated from the samples. The isolated strains resembled Taylorella equigenitalis. Both species are catalase, oxidase and alkaline phosphatase positive, but, in addition to these characteristics, B. ureolyticus strains produced urease and they could not tolerate 10% O2. They also failed to be agglutinated in a hyperimmune serum raised against T. equigenitalis; however, B. ureolyticus and T. equigenitalis were agglutinated in the slide agglutination test in a serum produced against one of the B. ureolyticus isolates. Further investigations are needed to clarify the pathologic role of B. ureolyticus in genital infections of mares and other animals.

M. Peters

Papers

Isolation of Bacteroides ureolyticus from vaginal discharge of mares.