In conclusion, this study showed that M. hyopneumoniae
isolates differ between herds and, in some cases, even
within the same herd in Canada. Moreover, almost half of
the field isolates presented less than 55% homology with
selected vaccine and reference strains. Isolates did not
group according to virulence but the absence of a specific
MLVA locus was significantly associated with less severe
lesions and lower numbers of bacteria.