Symposium review: The uterine microbiome associated with the development of uterine disease in dairy cows

摘要

Until 2010, our knowledge of the uterine microbiomein cows that developed uterine disease relied almostexclusively on culture-dependent studies and mostlyincluded cows with clinical endometritis (i.e., withpurulent uterine discharge). Those studies consistentlyfound a strong positive correlation between Trueperellapyogenes and clinical endometritis, whereas otherpathogens such as Escherichia coli, Fusobacterium necrophorum,Prevotella melaninogenica, and Bacteroidesspp. were also commonly cocultured. In contrast, Streptococcusspp., Staphylococcus spp., and Bacillus spp.were usually isolated from healthy cows. Starting in2010, culture-independent studies using PCR exploredthe microbiome of cows with metritis and clinical endometritis,and observed that E. coli was a pioneerpathogen that predisposed cows to infection with F.necrophorum, which was strongly associated with metritis,and to infection with T. pyogenes, which wasstrongly associated with clinical endometritis. Startingin 2011, culture-independent studies using metagenomicsequencing expanded our knowledge of the uterine microbiome.It has been shown that cows have bacteria inthe uterus even before calving, they have an establisheduterine microbiome within 20 min of calving, and thatthe microbiome structure is identical between cows thatdevelop metritis and healthy cows until 2 d postpartum,after which the bacterial structure of cows thatdeveloped metritis deviates in favor of greater relativeabundance of Bacteroidetes and Fusobacteria and lesserrelative abundance of Proteobacteria and Tenericutes.The shift in the uterine microbiome in cows that developmetritis is characterized by a loss of heterogeneityand a decrease in bacterial richness. At the genus level,Bacteroides, Porphyromonas, and Fusobacterium havethe strongest association with metritis. At the specieslevel, we observed that Bacteroides pyogenes, Porphyromonaslevii, and Helcococcus ovis were potentialemerging uterine pathogens. Finally, we have shownthat the hematogenous route is a viable route of uterineinfection with uterine pathogens. Herein, we proposethat metritis is associated with a dysbiosis of the uterinemicrobiota characterized by decreased richness, andan increase in Bacteroidetes and Fusobacteria, particularlyBacteroides, Porphyromonas, and Fusobacterium.