Sazonalidade e susceptibilidade antimicrobiana da microbiota ocular de bovinos de uma microrregião do Cerrado do estado de Mato Grosso, Brasil

Abstract

The conjunctiva and cornea are the main sites affected by ophthalmopathies in cattle, these changes lead to painful processes and thus can cause several economic losses. Healthy eyes have a natural microbiota, which when in balance does not usually generate eye infections, however in some situations such as trauma or stress, these can become potentially pathogenic. The moraxella spp. is a gram negative bacterium, and the etiologic agent of infectious bovine keratoconjunctivitis (IBK), which is an important ophthalmological condition that affects cattle. Thus, the objective was to detect the presence of Moraxella spp. in the normal conjunctiva of cattle without clinical signs of infectious bovine keratoconjunctivitis and to determine the bacterial prevalence in isolates from the healthy conjunctival sac of dairy cattle and beef cattle, in two different periods of the year (drought and rain) in a microregion of the State of Mato Grosso . A total of 144 swabs were collected from the conjunctival sac, 74 from dairy cattle corresponding to the rainy (39) and dry (35) seasons and 70 from beef cattle in the rainy (35) and dry (35) seasons. Bacterial isolates were identified using Gram stain and biochemical tests to classify the genus. In total, 12 different bacterial genera were isolated, with a prevalence of Gram-positive agents in the dry season and Gram-negative agents in the rainy season in both evaluated categories. The predominant bacterium isolated was Bacillus cereus (75.69%). The detection of Moraxella was performed by PCR, of the 144 samples submitted to this analysis, 12 (8.33%) amplified a fragment of 600bp. Of these, 5 were dairy cattle in the rainy season and 7 were beef cattle in the dry season. In order to confirm the species of Moraxella, a PCR product was submitted to sequencing and compared to the BLAST-n database, where it showed 98.86% identity with Moraxella bovoculli. The study demonstrated that the ocular microbiota of cattle undergoes variations with climatic seasonality. Although the animals in the study did not show clinical signs of IBK and even though there was no growth of bacteria of the Moraxella genus in the culture, it was detected by PCR.