Oral Technical Session: Fungal Epidemiology
151-O
Emergence of a new population of the select agent Rathayibacter toxicus
J. P. STACK (1), M. Arif (1), G. Y. Busot (1), R. Mann (2), B. Rodoni (2), S. Liu (1)
(1) Kansas State Univ, Manhattan, KS, U.S.A.; (2) Victoria Department of Environment and Primary Industries, Bundoora, Australia
The U.S. Select Agent Rathayibacter toxicus is a toxigenic gram-positive bacterium responsible for a lethal disease of livestock and wildlife in Australia. The genetic structure of R. toxicus populations was determined to evaluate the efficacy of detection protocols and to understand the potential for emergence of new strains. Two genetic analyses were applied to 54 isolates of R. toxicus collected in Australia from 1973 to 2014; multi-locus sequence typing (MLST) and inter-simple sequence repeat (ISSR) analysis. Commonly used MLST gene targets detected no genetic variation among these 54 R. toxicus isolates. An MLST based on seven strategically selected genes representing an array of cellular functions from metabolism and replication to cell defense detected substantial genetic variation. The concatenated MLST sequences comprised 5533 bp (0.2% of the 2.369 Mb R. toxicus genome). Analysis of the MLST data partitioned the 54 isolates into three distinct populations. To analyze the genome more generally, a total of 94 ISSR loci (69% polymorphic) were generated using ten ISSR primers. Both the gene-based MLST and the neutral-locus ISSR analyses resolved the same three distinct populations of R. toxicus, designated population-A, -B and -C. Population-A isolates/genotypes were not represented in archived culture collections nor were they previously reported; population-A may be comprised of emerging isolates of R. toxicus.