Strain difference of mouse in susceptibility to Mycoplasma pulmonis infection.

Abstract

Strain difference in susceptibility to M. pulmonis infection was studied in mice of 5 strains by cage-mating with previously infected ones. The organisms were isolated abundantly from the upper respiratory tracts of all mice examined within one week after contact, and did not disappear throughout the observation period of 11 to 16 weeks. However, a remarkable strain difference was demonstrated in development of gross pneumonic lesions by indication of the fact that the lesions appeared in 40 to 70% of ICR mice after 3 weeks of contact, while less than 10% of ddY mice. In NIH, CF#1 and C3H/He mice, the lesions were detected at various rates less than 40%. Growth of the organisms in the trachea was not significantly different between ICR and ddY mice, in contrast with numbers of the organisms in the lung which were less than 103 CFU/g in many of ddY mice but 10&lt5-10&gt CFU/g in 24 of 40 ICR mice examined on the 3rd week of contact and thereafter. All lungs with pneumonic lesions harbored more than 105 CFU/g organisms, while grossly normal lungs less than 105 CFU/g. CF antibody appeared in almost all mice during the first and second weeks of contact, and reached to a peak of titer (1:64 to 1:1, 024) on the 3rd week in both ddY and ICR mice. Titers of the antibody decreased from the 8th week in ddY mice, but persisted in ICR mice till the 10th week.