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.

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Infectious bovine keratoconjunctivitis (IBK) is an economically significant disease caused by the Gram-negative bacterium Moraxella bovis. Moraxella bovoculi also secretes virulence factors and is the most frequently isolated species from bovine eyes during IBK outbreaks. Whole genome sequencing has presented extensive genetic differences between M. bovoculi isolated from the eye and nasopharynx (NP) of cattle with and without IBK. At present, distinguishing between Moraxella species in clinical laboratory specimens is time consuming and relies on expensive and complex biochemical testing, of which reactions are not always consistent. Nucleic acid assays (PCR RFLP) can distinguish species, but can be costly and do not work on all strains. Identification of the specific etiologic agent during an IBK outbreak is critical to assist veterinarians implement the proper prevention and treatment strategies. Matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry is an emerging tool in bacterial identification that is rapid, inexpensive, and provides advantages over current identification methods. The overall goal of this study was to determine the accuracy of the MALDITOF MS method as applied to Moraxella spp isolated from bovine eyes and compare it to existing identification methods.