Effects of viral and mycoplasmal infections, ammonia exposure, vitamin A deficiency, host age, and organism strain on adherence of Mycoplasma pulmonis in cultured rat tracheas

Abstract

Adherence to host cells is thought to be a pathogenetic mechanism in mycoplasmal diseases, thus, factors affecting adherence could affect disease expression. To determine whether factors that affect expression of Mycoplasma pulmonis respiratory disease in rats alter adherence of the organism to respiratory epithelium, we studied adherence of radiolabelled M. pulmonis in perfused whole rat tracheas. Adherence was significantly increased in tracheas from rats with sialodacryoadenitis virus infection or vitamin A deficiency (103 +/- 16% and 112 +/- 29% of control means, respectively), but Sendai virus infection, ammonia exposure, and host age (40 versus 8 weeks) were not associated with increased adherence. We also assessed the relationship between adherence and virulence of M. pulmonis strains. The virulent strain 5782C was more adherent (51 +/- 7%) than the type strain, PG34(Ash), and a polystyrene-adherent, hemadsorbing UAB CT subclone was more adherent (229 +/- 40%) than a UAB CT subclone that does not adhere to polystyrene or erythrocytes. PG34(Ash) and the UAB CT subclones caused rhinitis only; however, the adherent UAB CT subclone caused significantly more severe rhinitis than either the nonadherent subclone or PG34(Ash) as determined by scoring of histologic sections. To determine whether M. pulmonis itself induces changes in respiratory epithelium resulting in enhanced adherence, we studied adherence in tracheas from rats inoculated with M. pulmonis 3 weeks earlier. Adherence was increased 64 +/- 22%, compared with that in tracheas from control rats. Adherence in infected tracheas treated with tetracycline for 2 days was not increased, indicating that M. pulmonis-induced changes in epithelial adherence are rapidly resolved after elimination of infection.