Corynebacterium uterequi in the uterus of a mare from Rio Grande do Sul, Brazil

ABSTRACT: Corynebacterium uterequi has been isolated from mares with infertility and early embryonic loss in mares from select herds of Europe and South Africa, but there is limited information regarding its occurrence and pathogenic role in other regions. This study described the laboratorial characteristic of uterine isolates of Corynebacterium sp. from mares with reproductive disorders in Rio Grande do Sul state (Brazil), and the associated cytological and histopathological findings. Considering the lack of data on the characteristics of this bacterial agent and its role in reproductive disorders in mares, microbiological culture and cytological and histopathological analyses were conducted in samples of thirty mares with reproductive disorders. Corynebacterium sp. was isolated from uterine samples of twelve mares, either as the sole bacterial isolate (n = 6) or in combination with other bacterial species (n = 6). Microbiological analysis of the isolates revealed morphological and biochemical profiles highly similar to C. uterequi. Molecular analysis of the 16S rRNA and rpoB gene regions from one isolate revealed high nucleotide identity - 99.38% and 100%, respectively - with C. uterequi sequences available in GenBank (accession number CP011546.1). Cytological evaluation revealed moderate to severe inflammation in eight of the twelve mares from which Corynebacterium sp. was isolated. Among these eight, inflammation was observed in two mares with Corynebacterium sp. only and in six mares where Corynebacterium sp. was isolated in combination with other bacteria. Histopathology of endometrial biopsies revealed glandular and periglandular fibrosis, periglandular nests, and glandular ectasia in two samples and lymphoplasmacytic endometritis in another. Additionally, two mares among the six that had Corynebacterium sp. as the sole isolate in uterine swabs presented multifocal periglandular fibrosis with nest formation and glandular ectasia. Hence, our study showed C. uterequi circulation in mares from Brazil and our findings contributed to the knowledge of selected aspects of this agent.