|HILLE, MATTHEW - University Of Nebraska|
|ROBBINS, KARA - University Of Nebraska|
|Clawson, Michael - Mike|
|LOY, JOHN - University Of Nebraska|
Submitted to: Journal of Microbiological Methods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2020
Publication Date: 5/11/2020
Citation: Hille, M., Dickey, A.M., Robbins, K., Clawson, M.L., Loy, J.D. 2020. Rapid differentiation of Moraxella bovoculi genotypes 1 and 2 using MALDI-TOF mass spectrometry profiles. Journal of Microbiological Methods. 173:105942. https://doi.org/10.1016/j.mimet.2020.105942.
Interpretive Summary: Infectious Bovine Keratoconjunctivitis (IBK) or pinkeye is a common, highly contagious disease in beef cattle that can result in reduced performance, substantial pain, and blindness. Moraxella bovoculi is a bacterial species commonly found in cattle eyes with and without IBK. Previous research has shown that there are two major strains, or “genotypes” of M. bovoculi in cattle (1 and 2), and while both genotypes can be found in healthy cattle eyes, genotype 2 strains have not been found in IBK eyes and genotype 1 strains have. This indicates that genotype 1 strains, in particular, likely have a significant contributory role to IBK. Recently, a technology known as of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been introduced to veterinary diagnostic labs as a quick and easy platform to identify bacteria at the species and subspecies (genotype) level. This study reports a new MALDI-TOF MS test that is 100% accurate in identifying the two M. bovoculi genotypes. This test can be used without restriction in veterinary diagnostic labs and may be useful in the rapid identification of M. bovoculi strains involved in IBK outbreaks.
Technical 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.