CHARACTERIZATION OF LAWSONIA-INTRACELLULARIS GEN-NOV, SP-NOV, THE OBLIGATELY INTRACELLULAR BACTERIUM OF PORCINE PROLIFERATIVE ENTEROPATHY

A novel obligately intracellular bacterium, ileal symbiont intracellul aris, which was obtained from the intestines of pigs with proliferativ e enteropathy disease, was grown in pure cocultures with tissue cultur es of rat cells, An examination of the 16S ribosomal DNA gene sequence revealed that the isolates which vie obtained are members of the delt a subdivision of the Proteobacteria and that the sequences of these or ganisms exhibit a level of similarity of 91% with the sequence of Desu lfovibrio desulfuricans ATCC 27774. These isolates were homogeneous an d differed in cellular morphology, acid fastness, phenotype, electroph oretic protein profile, and habitat from Desulfovibrio species, On the basis of the results of an integrated study of the phenotype and geno type of a consistent morphological entity found in particular porcine cells and associated with a well-defined clinical condition, we conclu ded that these bacteria belong to a previously undescribed genus and S pecies; for which we propose the name Lawsonia intracellularis gen, no v., sp, nov, A species-specific recombinant DNA probe was cloned previ ously, and this probe was used to identify the bacterium in tissue cul ture cells and in the ileal epithelia of pigs with proliferative enter opathy disease. Coculture of the organism with a rat enterocyte cell l ine allowed us to designate strain NCTC 12656 the type strain and to d escribe the new genus and species. The organism which we cultured is p athogenic for pigs and causes proliferative enteropathy lesions in the ir ilea and colons, and Koch's postulates were fulfilled for this orga nism.