Observations of the carrier state in hamsters infected with Leptospira interrogans serotype pomona

Summary A variation betweenLeptospira interrogens serotype pomona strains 3341 and MLS acute to become established in the kidney of the hamster and to produce a temporary shedding state in the urine is described. The 3341 strain readily localized in the proximal tubules of the kidney and all infected hamsters became good shedders. Leptospiruria lasted for approximately 100 post-inoculation days. The observation of few spirochetes in the renal tubules, the low incidence of positive cultures from kidney tissue and urine and the low counts of leptospires in the urine characterized the MLS acute strain as a poor shedding strain.A MLS strain (MLS chronic) was isolated from the kidney tissue of a hamster killed on the 100th post-inoculation day. Upon subsequent inoculation into hamsters, this strain produced a shedding state similar to that of the 3341 strain. When compared with the 3341 strain, the MLS chronic strain showed a lower leptospiral count in the urine as well as a greater lag phase until the maximum count was reached.Comparative studies on the 3341, MLS acute, and chronic strains indicated that the MLS chronic strain was probably a mutant because of its rare and spontaneous occurrence and the retention of its shedding characteristic after numerous passages in hamsters and artificial media.This study was supported by a contract, Nonr-3718(02), NR 103-522, between the Office of Naval Research, Department of the Navy, and the University of Nebraska.The technical assistance of Mr. Dick Miller, Miss Rose Reynolds, Mr. James Smith and Mrs. E. Karnish are gratefully acknowledged.