Caracterização de Corynebacterium sp. isolado do útero de éguas do sul do Brasil

Abstract

The state of Rio Grande do Sul has a significant equine population, totaling approximately five hundred thousand head in 2021. Reproduction is an important activity developed in these animals and therefore reproductive problems can represent physiological and genetic losses. One of the main factors responsible for these disorders is endometritis, which can be physiologic but can evolve into a pathological process and, consequently, reduce the fertility of mares. Many factors may be associated with endometritis, mainly infection by microorganisms such as Streptococcus equi subsp. zooepidemicus and Escherichia coli. In 2013, a new bacterial species was isolated from mares with reproductive problems in Europe, and it was named Corynebacterium uterequi and in 2022, this same microorganism was isolated from mares in South Africa that shown fertility problems. Since the real involvement of this bacterium in the occurrence of uterine lesions and infertility in mares is still unknown, its distribution and characteristics should be investigated. Therefore, the aim of this study was to characterize Corynebacterium sp. isolated from uterine samples of mares with reproductive problems in a stud farm in Rio Grande do Sul, and to describe the cytological and histopathological findings of mares positive for this microorganism. For this, 30 uterine samples collected from mares from a stud farm in São Borja (RS), with a history of reproductive problems, were submitted to laboratory analysis (culture, cytology and histopathology). For bacterial culture, swab samples were inoculated in agar enriched with 5% sheep blood and MacConkey agar. After 48 hours of incubation in aero and microaerobiosis, Corynebacterium sp. was isolated from twelve samples, associated or not with other microorganisms. In the morphological and biochemical analysis, the isolates showed characteristics highly similar to that of C. uterequi obtained from mares in Europe and South Africa. Molecular analysis of the 16S RNA and rpoB regions indicated that the isolates have high identity with C. uterequi deposited in Genbank (99.38% and 100%, respectively). In the cytological evaluation of the uterus of mares positive for Corynebacterium sp. the cellularity indicative of inflammation was observed in eight samples (8/12). In the uterine biopsy, alterations compatible with glandular and periglandular fibrosis were observed in six samples (6/12), and in one case there was formation of a periglandular nest and glandular ectasia and, besides, characteristic lesions of lymphoplasmacytic endometritis were observed in another case. These results do not allow establishing whether C. uterequi isolated from mares in Rio Grande do Sul belongs to the microbiota or whether it is an agent that causes lesions, since it was detected both in animals with uterine alterations and without histological alterations. However, this work contributed to the knowledge of the epidemiology, clinic, pathology and diagnosis of this new species, in addition to demonstrating its circulation in mares in Southern Brazil.