Whole genome sequencing of Moraxella bovis strains from North America reveals two genotypes with different genetic determinants

Abstract

Background Moraxella bovis and Moraxella bovoculi both associate with infectious bovine keratoconjunctivitis (IBK), an economically significant and painful ocular disease that affects cattle worldwide. There are two genotypes of M. bovoculi (genotypes 1 and 2) that differ in their gene content and potential virulence factors, although neither have been experimentally shown to cause IBK. M. bovis is a causative IBK agent, however, not all strains carry a complete assortment of known virulence factors. The goals of this study were to determine the population structure and depth of M. bovis genomic diversity, and to compare core and accessory genes and predicted outer membrane protein profiles both within and between M. bovis and M. bovoculi. Results Phylogenetic trees and bioinformatic analyses of 36 M. bovis chromosomes sequenced in this study and additional available chromosomes of M. bovis and both genotype 1 and 2 M. bovoculi, showed there are two genotypes (1 and 2) of M. bovis. The two M. bovis genotypes share a core of 2015 genes, with 121 and 186 genes specific to genotype 1 and 2, respectively. The two genotypes differ by their chromosome size and prophage content, encoded protein variants of the virulence factor hemolysin, and by their affiliation with different plasmids. Eight plasmid types were identified in this study, with types 1 and 6 observed in 88 and 56% of genotype 2 strains, respectively, and absent from genotype 1 strains. Only type 1 plasmids contained one or two gene copies encoding filamentous haemagglutinin-like proteins potentially involved with adhesion. A core of 1403 genes was shared between the genotype 1 and 2 strains of both M. bovis and M. bovoculi, which encoded a total of nine predicted outer membrane proteins. Conclusions There are two genotypes of M. bovis that differ in both chromosome content and plasmid profiles and thus may not equally associate with IBK. Immunological reagents specifically targeting select genotypes of M. bovis, or all genotypes of M. bovis and M. bovoculi together could be designed from the outer membrane proteins identified in this study.

Genotype classification of Moraxella bovis using MALDI-TOF MS profiles

“…Thirty seven of the 39 strains of M. bovis used for this study had previously undergone bacterial identification, whole genome sequencing and assembly into closed, circular chromosomes, and were classified according to genotype ( Wynn et al, 2022 ). An additional two strains were genotyped from Illumina libraries using two methods: First, Illumina library fastq files were converted to fasta BLAST databases ( Camacho et al, 2009 ) and previously identified genotype 1 and 2 specific genes ( Wynn et al, 2022 ) were used as BLAST queries to find genotype specific gene sequence in the Illumina libraries. The strains consisted of ten genotype 1 and 29 genotype 2 strains.…”

“…A secreted repeats-in-toxin (RTX) exotoxin and a type IV pilus protein are the two main virulence factors possessed by M. bovis required for IBK development ( Jayappa and Lehr, 1986 ; Clinkenbeard and Thiessen, 1991 ; Ruehl et al, 1993 ; Beard and Moore, 1994 ). Recently, two distinct genotypes of M. bovis were characterized that shared a core of 2,015 genes with an additional 121 genes specific to genotype 1 and 186 genes specific to genotype 2 ( Wynn et al, 2022 ). The genotypes possess different sequence variants of RTX and different plasmid profiles.…”

Moraxella oculi sp. nov., isolated from a cow with infectious bovine keratoconjunctivitis

“…Virulence factors associated with Moraxella species that contribute to the clinical disease include an RTX toxin, which is a cytotoxin that creates the lytic eye lesions and is also necessary for the in vitro haemolytic activity of the organisms, and a type IV pilin (gene pilA), which is considered necessary for bacterial attachment [2]. However, these virulence factors may not be detected in all strains of the various Moraxella species detected from cattle, which confounds determination of IBK causality [4,5]. The identification of new species of Moraxella from cattle, including from both the nose, as mentioned previously [1], and the eye, as we initially reported and proposed with the name 'Moraxella oculobovii' [6], and described herein, complicates this further.…”

Metagenomic Analysis and Identification of Epizootic Strains of the Causative Agent of Infectious Bovine Keratoconjunctivitis in Kazakhstan

“…are detected (Kneipp 2021). Infectious keratoconjunctivitis of cattle is an acute, contagious, rapidly spreading disease characterized by lacrimation, photophobia, hyperemia of conjunctivitis vessels, blepharospasm, iridospasm, serous-mucous and serouspurulent discharge from the affected eyes, and opacification and ulceration of the cornea (Subbotin et al 2014;Maboni et al 2015;Wynn et al 2022). This disease can infect up to 80% of a herd within 3 weeks (Jeyabal et al 2013).…”