Abstract
Bacterial overgrowth in the uterus is a normal event after parturition. In contrast to the healthy cow, animals unable to control the infection within 21 days after calving develop postpartum endometritis. Studies on the Microbial Ecology of the bovine reproductive tract have focused on either vaginal or uterine microbiomes. This is the first study that compares both microbiomes in the same animals. Terminal Restriction Fragment Length Polymorphism of the 16S rRNA gene showed that despite large differences associated to individuals, a shared community exist in vagina and uterus during the postpartum period. The largest changes associated with development of endometritis were observed at 7 days postpartum, a time when vaginal and uterine microbiomes were most similar. 16S rRNA pyrosequencing of the vaginal microbiome at 7 days postpartum showed at least three different microbiome types that were associated with later development of postpartum endometritis. All three microbiome types featured reduced bacterial diversity. Taken together, the above findings support a scenario where disruption of the compartmentalization of the reproductive tract during parturition results in the dispersal and mixing of the vaginal and uterine microbiomes, which subsequently are subject to differentiation. This differentiation was observed early postpartum in the healthy cow. In contrast, loss of bacterial diversity and dominance of the microbiome by few bacterial taxa were related to a delayed succession at 7DPP in cows that at 21 DPP or later were diagnosed with endometritis.
Highlights
Uterine infection is a common event in the postpartum period in cattle [1]
Changes associated with later development of postpartum endometritis were observed as early as 7 days postpartum (DPP), a time when vaginal and uterine microbiomes were most similar
These included the loss of bacterial Operational Taxonomic Units (OTUs) present in healthy cows and the appearance of a subcommunity associated with the development of postpartum endometritis
Summary
Uterine infection is a common event in the postpartum period in cattle [1]. Early postpartum endometrial inflammation has been shown to occur in response to infection and tissue damage, and as a pre-requisite for uterine involution in preparation for a future pregnancy [2,3]. Studies to identify possible aetiological agent(s) of postpartum uterine infection were focused on the isolation of bacteria from diseased animals [5,6,7,8]. Postpartum endometritis often results from non-specific infections [8], the most common pathogens associated with the uterus of endometritic animals are Escherichia coli, Trueperella pyogenes, Prevotella melaninogenicus and Fusobacterium necrophorum [5,9]. These bacteria are often associated in mixed infections of the uterus, with evidence pointing to a succession in which E. coli is most prevalent in metritic cows during the first week postpartum. Its presence increases the subsequent risk of infection by T. pyogenes in postpartum weeks 2 and 3, which in turn has been associated with postpartum endometritis [9,10]
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