Location: Animal Health GenomicsTitle: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification of Moraxella bovoculi and Moraxella bovis isolates from cattle
|ROBBINS, KARA - University Of Nebraska|
|Clawson, Michael - Mike|
|LOY, JOHN - University Of Nebraska|
Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2018
Publication Date: 7/20/2018
Publication URL: http://handle.nal.usda.gov/10113/6156707
Citation: Robbins, K., Dickey, A.M., Clawson, M.L., Loy, J.D. 2018. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification of Moraxella bovoculi and Moraxella bovis isolates from cattle. Journal of Veterinary Diagnostic Investigation. p. 1-4. Available: jvdi.sagepub.com. https://doi.org/10.1177/1040638718789725.
Interpretive Summary: Infectious bovine keratoconjunctivitis (IBK), also known as “pinkeye”, is a common eye disease of cattle. IBK is highly contagious and cattle afflicted with it can experience excessive tear flow and blinking, eye pain on exposure to light, inflammation of the cornea, ocular rupture, and blindness. IBK is caused by members of the bacterial species Moraxella bovis, which have a number of virulence factors. A related, recently described bacterial species, Moraxella bovoculi, has not been reported to cause IBK, but is suspected in having a significant role in the disease. This is because M. bovoculi has been isolated more frequently than M. bovis from cattle eyes with IBK. Additionally, some strains of M. bovoculi have virulence factors very similar to M. bovis, whereas other strains do not. Consequently, an ability to identify both M. bovis and M. bovoculi is important to veterinary diagnostic labs that routinely receive samples from IBK outbreaks. In this study, three methods for identifying M. bovis and M. bovoculi isolates were compared. To facilitate the comparisons, whole or partial genome sequence of the isolates was used as a gold standard for their actual identity. The three methods were 1) a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay, 2) a matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) assay that referenced a default identification database (BDAL) provided by the instrument manufacturer, and 3) a MALDI-TOF MS assay that referenced a customized identification database created by the authors of this study (UNLVDC). The UNLVDC database contained all of the information of the BDAL database, and additional strain information for both M. bovis and M. bovoculi. Of the three methods, MALDI-TOF MS referencing the customized UNLVDC database most effectively identified M. bovis and M. bovoculi isolates from cattle. MALDI-TOF MS has distinct workflow advantages over PCR-RFLP, which make it a preferable platform for identifying M. bovis and M. bovoculi, especially when used with the UNLVDC database. Reference data files from the strains used to create the UNLVDC database are freely available for MALDI-TOF users that are interested in identifying M. bovis or M. bovoculi isolates from cattle.
Technical Abstract: Infectious bovine keratoconjunctivitis (IBK) is an economically significant disease caused by Moraxella bovis. Moraxella bovoculi, although not reported to cause IBK, has been isolated from the eyes of cattle diagnosed with IBK. Identification of M. bovis and M. bovoculi can be performed using biochemical or DNA-based approaches, both of which may be time consuming and inconsistent between laboratories. We conducted a comparative evaluation of M. bovoculi and M. bovis identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with a database provided by Bruker Daltonics (termed the BDAL database), the BDAL database supplemented with spectra generated in our study (termed the UNLVDC database), and with PCR–restriction-fragment length polymorphism (PCR-RFLP) typing. M. bovoculi (n = 250) and M. bovis (n = 18) isolates from cattle with or without IBK were used. MALDI-TOF MS using the UNLVDC database correctly identified 250 of 250 (100%) of M. bovoculi and 17 of 18 (94%) of M. bovis isolates. With the BDAL database, MALDI-TOF MS correctly identified 249 of 250 (99%) of M. bovoculi and 7 of 18 (39%) of M. bovis isolates. In comparison, the PCR-RFLP test correctly identified 210 of 250 (84%) of M. bovoculi and 12 of 18 (66%) of M. bovis isolates. Thus, MALDI-TOF MS with the UNLVDC database was the most effective identification methodology for M. bovis and M. bovoculi isolates from cattle.