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Infect Immun. 1973 November; 8(5): 694-699
Copyright © 1973 American Society for Microbiology. All Rights Reserved.

Infection at the Subcellular Level II. Distribution and Fate of Intravenously Injected Brucellae Within Phagocytic Cells of Guinea Pigs

^a Departments of Microbiology and Immunology, and Cell Biology, Baylor College of Medicine, Houston, Texas 77025

ABSTRACT

Cells of Brucella melitensis strain 16 M were labeled with ³²P. When injected into normal guinea pigs, labeled, viable bacteria were taken up and inactivated in liver and spleen during the 60 min after infection. Both uptake and inactivation increased if brucellae were coated with antibrucella antibody. Neither viability nor radioactivity were lost when labeled brucellae were incubated for 60 min in vitro with normal guinea pig blood, liver homogenates, or in defined medium. Incubation for 12 h with antibrucella rabbit immunoglobulin G similarly was innocuous. Livers were removed from infected animals at various times up to 60 min after injection and were separated into subcellular fractions. The numbers of total (determined by radioactivity measurements) and viable brucellae as well as the acid phosphatase activity in the various fractions were determined. Total bacteria and acid phosphatase activity were progressively transferred from the mitochondrial plus light mitochondrial (M + L) fraction to the nuclear (N) fraction. Viability of brucellae declined more rapidly in the N fraction than in other fractions. Examination of M + L fractions by isopycnic centrifugation showed a decrease in viability of both free brucellae and those in particles. The results indicated the formation of bacteria-containing heterolysosomes which progressively increased in size and in which brucellae were inactivated. The antibrucella activity of phagocytes of guinea pig liver in vivo appeared to be greater than that of peritoneal macrophages from immune rabbits or of bovine leukocytes studied in vitro.

¹ Present address: Instituto de Medicina Tropical Alexander von Humbolt, Universidad Peruana Cayetano Heredia, Apartado Postal 5045, Lima, Peru.