Experimental infection of C3H mice with avian, porcine, or human isolates of Serpulina pilosicoli.

C3H/HeJ (lps(d)/lps(d)) and C3H/HeOuJ (lps(n)/lps(n)) mice were infected via gastric intubation with avian, porcine, or human isolates of weakly hemolytic spirochetes classified as Serpulina pilosicoli. Upon histopathological examination of cecal tissue from mice infected with avian or porcine isolates, colonization of spirochetes attached end-on to the apical surface of enterocytes was observed. There were no apparent differences in severity of cecal lesions between the lipopolysaccharide (LPS)-responsive (C3H/HeOuJ) and LPS-hyporesponsive (C3H/HeJ) mouse strains infected with these isolates. Transmission electron microscopy showed spirochetes invaginated into the host cell membrane with resultant effacement of microvilli and loss of the glycocalyx. End-on attachment of the human isolate S. jonesii was not observed in the present studies, although weakly hemolytic spirochetes were reisolated from mice infected with S. jonesii. Moreover, results of Western immunoblot experiments showed mice developed serum antibody responses to the S. pilosicoli isolates examined. Thus, the present results indicate that specific isolates of S. pilosicoli can colonize mice and exhibit end-on attachment to cecal enterocytes.