Abstract
Moraxella bovoculi is the most frequently isolated bacteria from the eyes of cattle with Infectious Bovine Keratoconjunctivitis (IBK), also known as bovine pinkeye. Two distinct genotypes of M. bovoculi, genotype 1 and genotype 2, were characterized after whole genome sequencing showed a large degree of single nucleotide polymorphism (SNP) diversity within the species. To date, both genotypes have been isolated from the eyes of cattle without clinical signs of IBK while only genotype 1 strains have been isolated from the eyes of cattle with clinical signs of IBK. We used 38 known genotype 1 strains and 26 known genotype 2 strains to assess the ability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to accurately genotype M. bovoculi strains using mass spectrum biomarkers. Mass spectrum data was analyzed with ClinProTools 3.0 software and six models were developed that classify strain genotypes with accuracies ranging from 90.6% - 100%. Finally, using four of the most genotype-specific peaks that also exhibited high peak intensities from the six automated models, we developed a customized model (UNL assisted model) that had recognition capability, validation, and classification accuracies of 100% for genotype classification. Our results indicate that MALDI-TOF MS biomarkers can be used to accurately discriminate genotypes of M. bovoculi without the need for additional methods.
Highlights
Infectious bovine keratoconjunctivitis (IBK) represents the most common ocular disease of cattle in the United States and worldwide (Brown et al, 1998; Killinger et al, 1977)
A recent large-scale retrospective study found that among diagnostic laboratory submissions from cases of cattle with Infectious Bovine Keratoconjunctivitis (IBK) throughout the United States, M. bovoculi was the only bacteria isolated in 64% of cases while M. bovis was the only bacteria isolated in only 22% of cases (Loy and Brodersen, 2014)
Using ClinProTools software we developed six distinct automated models that were able to accurately classify M. bovoculi strains according to known genotypes with accuracies ranging from 90.6% 100%
Summary
Infectious bovine keratoconjunctivitis (IBK) represents the most common ocular disease of cattle in the United States and worldwide (Brown et al, 1998; Killinger et al, 1977). A recent large-scale retrospective study found that among diagnostic laboratory submissions from cases of cattle with IBK throughout the United States, M. bovoculi was the only bacteria isolated in 64% of cases while M. bovis was the only bacteria isolated in only 22% of cases (Loy and Brodersen, 2014). This is similar to a recent study showing detection of M. bovoculi using PCR based methods in more than 75% of samples submitted to a veterinary diagnostic lab (Zheng et al, 2019). The USDA granted conditional approval of a M. bovoculi bacterin for IBK prevention (USDA CVM code: 2A77.00, Addison Biological Laboratory, Inc. # 355) highlighting the potential importance of the contribution of these organisms to IBK
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