Genotyping of Mycoplasma hyorhinis using multiple-locus variable number tandem repeat analysis

Mycoplasma hyorhinis (M. hyorhinis) has re-emerged as an important swine pathogen in recent years causing significant economic losses in post weaning pigs. Genetic variability of M. hyorhinis has been described based on different molecular methods that have limited resolution and reproducibility. The present study was undertaken to develop a molecular epidemiological typing tool for M. hyorhinis based on multiple loci of variable number of tandem repeats in its genome, termed MLVA. The typing method was designed on the basis of the number of repeats in two hypothetical proteins, MHR_0152 and MHR_0298. A total of 205 samples were analyzed, including field isolates, clinical specimens, and a reference strain. Analysis of the combination of the 2 loci revealed 16 MLVA types in 165 of the 205 samples. In the remaining forty samples only one locus could be amplified. The most frequent types obtained from the set of samples were 8-4 (36.9%), 8-3 (11.5%), 7-4 (11.5%), 9-4 (10.9%) and 10-4 (9.3%). The Simpson's diversity index for the assay was D=0.814 when the 165 samples were taken into account. No clustering was observed based on the geographical location, sample type, or year of isolation or sampling. The MLVA assay developed in this investigation showed to be a reproducible and portable assay which could be easily performed and transferred to other laboratories. The use of this technique will assist in epidemiological investigations and can be used to improve the understanding the molecular biology of M. hyorhinis variants.