Tylosin tartrate and tiamutilin effects on experimental piglet pneumonia induced with pneumonic pig lung homogenate containing mycoplasmas, bacteria and viruses.

The effects of tylosin tartrate and tiamutilin were examined in pneumonias induced experimentally in neonatal piglets with a homogenate of pneumonic pig lung, obtained from pigs with naturally acquired enzootic pneumonia. The homogenate contained mycoplasmas, including Mycoplasma hyopneumoniae (M suipneumoniae) and M hyorhinis, and certain bacteria and viruses. The experimental pneumonias generally resembled mycoplasmal pneumonia histologically but were complicated by aspiration pneumonia in some animals. both tylosin tartrate (50 mg/kg) and tiamutilin (10 mg/kg) administered orally twice daily for 10 days, beginning 14 days after intranasal infection, significantly reduced the incidence and severity of macroscopical pneumonic lung lesions. M hyopneumoniae could be isolated from the lungs of the unmedicated piglets, but not from drug-treated piglets. The numbers of M hyorhinis, Acholeplasma granularum, Haemophilus parasuis, Pasteurella multocida and P haemolytica in the lung tissue of the infected piglets were significantly reduced by drug therapy. The role of bacterial in the experimental infection appeared to be that of secondary invaders.