Abstract
Although a number of common reproductive disorders in livestock involve bacterial infection, very little is known about their normal vaginal microbiota. Therefore, we sought to determine the species composition of sheep and cattle vaginal microbiota. Twenty Rambouillet ewes and twenty crossbred cows varying in age and reproductive status were sampled by ectocervicovaginal lavage. We amplified and sequenced the V3–V4 region of the 16S ribosomal RNA (rRNA) contents yielding a total of 907,667 high-quality reads. Good’s Coverage estimates indicated that we obtained data on 98 ± 0.01% of the total microbial genera present in each sample. Cow and ewe vaginal microbiota displayed few differences. Cow microbiota exhibited greater (P ≤ 0.05) α-diversity compared to the ewe microbiota. Both livestock species differed (P ≤ 0.05) from all previously reported vaginal communities. While bacteria were numerically dominant, Archaea were detected in 95% of cow and ewe samples, mainly of the order Desulfurococcales. Both ewes and cows were predominately colonized by the bacterial phyla Bacteroidetes, Fusobacteria, and Proteobacteria. The most abundant genera were Aggregatibacter spp., and Streptobacillus spp. Lactobacillus spp. were detected in 80% of ewe and 90% of cow samples, but only at very low abundances. Bacteria previously described from culture-based studies as common to the cow and ewe vaginal tract, except for Escherichia, were variably present, and only in low abundance. Ewe and cow pH differed (P ≤ 0.05), with means (±SD) of 6.7 ± 0.38 and 7.3 ± 0.63, respectively. In conclusion, 16S rRNA sequencing of cow and ewe vaginal ectocervicovaginal lavages showed that cow and ewe vaginal microbiota differ from culture-led results, revealing a microbiota distinct from previously described vaginal ecosystems.
Highlights
The human vaginal microbiota is most often dominated by lactobacilli [1]
The human vagina is most commonly dominated www.frontiersin.org by Lactobacillus spp. during their reproductive years [1], a recent study of non-human primates [5] has revealed this to be unique among the primate order
Our results contrast with preceding culture-based studies that have more commonly isolated genera such as Bacillus spp., Staphylococcus spp., and Streptococcus spp., from both cow and ewe vaginas as well as Corynebacterium spp., and Escherichia spp., from the ewe vagina and Enterococcus spp. from the cow vagina [6, 7, 9,10,11,12,13, 39]
Summary
The human vaginal microbiota is most often dominated by lactobacilli [1]. In this system, the lactobacilli are considered important to vaginal homeostasis through their production of lactate, which maintains a low vaginal pH (pH < 4.5) that is inhibitory to many vaginal pathogens [2]. Given the potential importance of vaginal lactobacilli in diminishing the risks of pregnancy-related complications, it is interesting to note that the vaginal microbiota of some humans [1] and all primates [5] do not display the same Lactobacillus-dominated vaginal ecosystems. The few culture-based studies that have been conducted on livestock have reported Lactobacillus spp. at lower abundances than other microbial genera in both the cow and ewe vagina [6,7,8]. No studies have been reported that have utilized culture-independent 16S ribosomal RNA (rRNA) sequencing of the cow or ewe vaginal microbiota. The complete reliance on culture has thereby left the true microbial diversity of the cow and ewe vagina hereinto undetermined and the scarcity of lactobacilli uncertain. The objective of this study was to elucidate the microbiota present in cow and ewe www.frontiersin.org
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