First report of Moraxella oculi in Brazil in an infectious bovine keratoconjunctivitis outbreak.

Abstract

Infectious Bovine Keratoconjunctivitis (IBK) is a widespread ocular disease that affects dairy and beef cattle worldwide, caused by Gram-negative bacteria from the genus Moraxella. It is the most common eye disease in cattle, with symptoms including tearing, ocular pain, corneal opacity, photophobia, ulceration, and, in severe cases, permanent blindness. This study focused on characterizing Moraxella species in a 2022 IBK outbreak in Minas Gerais, Brazil. Ocular swabs from 18 symptomatic Holstein cattle were analyzed through colony isolation, physiological tests, and molecular techniques, including PCR-RFLP and sequencing. Results revealed one isolate of Moraxella bovoculi genotype 1 and five isolates of Moraxella oculi, marking the first report of the latter species in Brazil. This study represents the second report of Moraxella oculi isolation and the first in a country different from the initial report. Notably, Moraxella bovis was not isolated in this outbreak. All isolates exhibited susceptibility to the tested antibiotics. Comparative genomic analysis between the Brazilian Moraxella oculi isolate and the American strain (Tifton 1) revealed 99.5% similarity in the 16-23 S rRNA locus and 99.0% average nucleotide identity.