In our study,peribronchiolar and perivascular lymphoid hyperplasia/cuffing and the accumulation of alveolar exudates were more pronounced in Hillcrest-challenged pigs
than in Beaufort-challenged pigs. Analysis of histopathological findings at the two time points revealed that all Hillcrest-challenged pigs had developed typical mycoplasmal pneumonia by 21 days post-challenge,whereas the majority of Beaufort challenged pigs developed focal mycoplasma pneumonia only by 28 days postinoculation.