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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Animal Health Genomics » Research » Publications at this Location » Publication #370836

Research Project: Genomic Intervention Strategies to Prevent and/or Treat Respiratory Diseases of Ruminants

Location: Animal Health Genomics

Title: Differentiation of Mannheimia haemolytica genotypes 1 and 2 by visible phenotypic characteristics on solid media

item Wynn, Emily
item Schuller, Genevieve - Gennie
item LOY, JOHN - University Of Nebraska
item Workman, Aspen
item McDaneld, Tara
item Clawson, Michael - Mike

Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/24/2020
Publication Date: 6/2/2020
Citation: Wynn, E.L., Schuller, G., Loy, J.D., Workman, A.M., McDaneld, T.G., Clawson, M.L. 2020. Differentiation of Mannheimia haemolytica genotypes 1 and 2 by visible phenotypic characteristics on solid media [abstract]. American Society for Microbiology Microbe, June 18-22, 2020, Chicago, Illinois. Poster No. 6696.

Interpretive Summary:

Technical Abstract: Mannheimia haemolytica is a gram-negative bacterium often found in the upper respiratory tract of ruminants. When cattle are stressed, M. haemolytica can invade their lungs and cause bovine respiratory disease (BRD). Not all strains of M. haemolytica associate equally with BRD. Two major genotypes of M. haemolytica have been identified in cattle (1 and 2). While both are found in the upper respiratory tract, genotype 2 strains are more frequently isolated from the lungs of cattle with BRD than genotype 1 strains. Recently, a matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) assay was developed that distinguishes the two genotypes based on MS biomarkers. However, this assay is performed on cultured bacterial colonies in the absence of preliminary genotype information; thus, limited or biased colony selection for MALDI-TOF MS testing could misrepresent genotype presence and/or frequencies within samples. Here we describe color and morphological differences between genotype 1 and 2 strains grown on solid media, and a method to visually distinguish them from each other without specialized equipment. Use of this method can help ensure that both genotypes, if present, are selected from BRD cultures and sent forward for confirmatory identification. This method will also enable the frequencies of each genotype to be estimated in mixed cultures. Ultimately, this will help determine the roles, or lack thereof, of either genotype in BRD cases, and may facilitate better treatment strategies for BRD outbreaks.