Multilocus sequence typing of Mycoplasma bovis reveals host-specific genotypes in cattle versus bison

Authors: Register, Karen; THOLE, LUKE - Iowa State University; ROSENBUSCH, RICARDO - Iowa State University; MINION, CHRIS - Iowa State University

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2014
Publication Date: 11/11/2014
Publication URL: http://handle.nal.usda.gov/10113/61363
Citation: Register, K.B., Thole, L., Rosenbusch, R., Minion, C. 2014. Multilocus sequence typing of Mycoplasma bovis reveals host-specific genotypes in cattle versus bison. Veterinary Microbiology. 175:92-98.

Interpretive Summary: Mycoplasma bovis causes mastitis, pneumonia and arthritis in cattle and is the bacterium isolated most frequently from bovine respiratory disease complex (BRDC). Recently, M. bovis has emerged as a significant health problem in bison, causing both respiratory disease and reproductive problems, including abortion. Whether isolates from cattle are genetically distinct from bison isolates is unknown. This study describes the development of a molecular typing method for M. bovis, called multilocus sequence typing (MLST), that distinguishes between isolates based on comparison of DNA sequences from several genes important for basic metabolic activities of the bacterium. Based on our evaluation of 94 cattle isolates from all over the world and 42 bison isolates from the United States and Canada, we identified 32 different strains. Strains found in cattle are unique from those found in bison, suggesting recent disease outbreaks in bison may be due to the emergence of novel genetic variants of M. bovis. No correlation was found between particular strains and disease presentation or geographic origin. The MLST data reported here were used to populate a newly created and publicly available, curated database to which researchers can contribute additional data from newly evaluated isolates. The MLST scheme and database provide novel tools for exploring the population structure of M. bovis and tracking the evolution and spread of strains.

Technical Abstract: Mycoplasma bovis is a primary agent of mastitis, pneumonia and arthritis in cattle and is the bacterium isolated most frequently from the polymicrobial syndrome known as bovine respiratory disease complex (BRDC). Recently, M. bovis has emerged as a significant health problem in bison, causing necrotic pharyngitis, pneumonia, dystocia and abortion. Whether isolates from cattle and bison comprise genetically distinct populations is unknown. This study describes the development of a highly discriminatory multilocus sequencing typing (MLST) method for M. bovis and its use to investigate the population structure of the bacterium. Genome sequences from six M. bovis isolates were used for selection of gene targets. Seven of 44 housekeeping genes initially evaluated were selected as MLST targets on the basis of sequence variability and distribution within the genome. For each gene target sequence, ranging in size from 312 bp to 574 bp, four to seven 7 alleles could be distinguished that, collectively, define 32 sequence types (STs) from a collection of 94 cattle isolates and 42 bison isolates. A phylogenetic tree based on the concatenated target gene sequences of each isolate reveals that bison isolates are genetically distinct from strains that infect cattle, suggesting recent disease outbreaks in bison may be due to the emergence of unique genetic variants. No correlation was found between ST and disease presentation or geographic origin. MLST data reported here were used to populate a newly created and publicly available, curated database to which researchers can contribute. The MLST scheme and database provide novel tools for exploring the population structure of M. bovis and tracking the evolution and spread of strains.