Abstract
Bacterial infections and inflammation of the uterus are common in dairy cattle after parturition. In particular, pathogenic bacteria that cause endometritis have been the focus of research in cattle reproduction in the last ten years. The aim of the present study was to identify commensal lactobacilli in the bovine uterus and to examine their influence on the synthesis of pro-inflammatory factors in bovine endometrial epithelial cells in vitro. Lactobacillus species were isolated from healthy bovine uteri and further characterised. Bovine endometrial epithelial cells in the second passage (n = 5 animals) were co-cultured with the autochthonous isolates L. buchneri, L. ruminis and L. amylovorus as well as with a commercially available L. vaginalis in different multiplicities of infection (MOI = 1, 5 and 10, respectively). Endometrial epithelial cells cultured without bacteria served as controls. At distinct points in time (2, 4 and 6 h) total RNA was extracted from co-cultured epithelial cells and subjected to reverse transcription quantitative PCR of pro-inflammatory factors. Furthermore, the release of such factors by co-cultured epithelial cells was measured by ELISA or EIA after 24 and 48 h. L. ruminis and L. amylovorus induced increased interleukin (IL) IL1A, IL6, IL8 and prostaglandin-endoperoxide synthase 2 mRNA levels and the release of IL8 and prostaglandin F2α in endometrial epithelial cells compared with control cells. In contrast, L. buchneri did not significantly influence the expression and release of these factors. Toll-like receptors 2 and 6 transcripts were found unchanged in co-cultured and untreated epithelial cells in vitro. However, endometrial epithelial cells of each animal showed individual differences in the response to bacterial load. These results suggest that Lactobacillus species are present in the bovine uterus, revealing immunomodulatory properties.
Highlights
Uterine bacterial invasion is common in dairy cattle after parturition
Sequencing with phylogenetic 16S rDNA primers identified these isolates as L. buchneri, L. ruminis, L. amylovorus, L. plantarum and L. similis
The microbiota present in the uterus of postpartum cows has been the subject of various studies over the last few decades [1,5,39,40], whereby the main focus was on pathogenic bacteria that cause uterine diseases such as metritis, and clinical and subclinical endometritis [2,41,42]
Summary
A wide range of different bacteria were isolated from samples collected from the uterus. [1,2,3,4] Commensal bacteria such as the genus Lactobacillus were detected in the uterus of cows, but not further investigated. Few studies have mentioned the culture of lactobacilli from uterine samples of cows [5,6], but their role in the uterine environment has not yet been elucidated. Lactobacilli are predominant in the human vaginal tract [9], where they play a role in maintaining the vaginal ecosystem in a healthy status by producing hydrogen peroxide, acetic and lactic acid and antibacterial molecules for a first defence against bacteria [10,11,12]
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