Dynamics of uterine infections with Escherichia coli, Streptococcus uberis and Trueperella pyogenes in post-partum dairy cows and their association with clinical endometritis

The diversity and dynamics of the uterine microbiota of dairy cows are poorly understood although it is becoming increasingly evident that they play a crucial role in the development of metritis and endometritis. Fourier-transform infrared (FTIR) spectroscopy was used to monitor the bovine microbiota of 40 cows on the day of calving and days 3, 9, 15, and 21 after parturition, and to investigate the associations of selected species with clinical endometritis (CE). Trueperella pyogenes (43.5%), Escherichia coli (21.5%), Bacillus spp. (21.0%) and Streptococcus uberis ( 18.5%) were the most frequently isolated microbes. Analyses of different sampling time points revealed that the presence of S. uberis on day 3 increased the risk of subsequent T. pyogenes infection on day 9 (odds ratio [OR] = 5.1, 95% confidence interval [CI] = 1.2–22.6). T. pyogenes infection (OR = 36.0, 95% CI = 3.8–343.2) and retained fetal membranes (RFM) (OR = 12.4, 95%CI = 1.4–112.7) were significant risk factors for CE. Cows with S. uberis on day 3 tended to have greater odds of CE than S. uberis -negative cows (OR = 7.1, 95% CI = 0.9–55.6). Chemometric analysis revealed significant differences in the metabolic profile of S. uberis strains isolated from cows with different vaginal discharge scores. This is the first study showing the association of specific S. uberis subtypes with the uterine health status of post-partum dairy cows. The study demonstrates that uterine clearance is a highly dynamic process, during which time bacteria show distinct patterns of progression, and provides information about interactions between bacterial species involved in the occurrence of CE.