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Infection and Immunity, June 1999, p. 2891-2900, Vol. 67, No. 6
Institute of Medical
Microbiology1 and Institute of
Pathology,
Received 9 March 1998/Returned for modification 11 May
1998/Accepted 17 March 1999
Melioidosis is an infectious disease caused by the saprophytic
gram-negative rod Burkholderia pseudomallei. The aim of
this study was to establish and characterize a murine model of
melioidosis to provide a basis for further investigations on the
pathogenesis of the disease. After intravenous infection with B. pseudomallei, C57BL/6 mice were found to be significantly more
resistant than BALB/c mice. There was a marked organotropism of
B. pseudomallei for the spleen and liver in both strains of
mice, with the highest bacterial load in the spleen. Electron
microscopic investigations of the spleen clearly demonstrated
intracellular replication within membrane-bound phagosomes. Electron
micrographs of the liver provided evidence that B. pseudomallei-containing phagosomes in hepatocytes fuse with
lysosomes, leading to degradation of bacteria. In both strains of mice,
the course of infection was highly dependent on the infective dose and
the bacterial strain used, ranging from death within a few days to
death after several weeks. In comparison with BALB/c mice, the
bacterial counts in C57BL/6 mice were decreased 12 h after
infection, which is suggestive of an innate immune mechanism against
B. pseudomallei in this early phase of infection contributing to the lower susceptibility of C57BL/6 mice. BALB/c mice
developed a more pronounced lymphopenia, granulocytosis, and
splenomegaly at a lower infective dose compared to C57BL/6 mice.
Analysis of the antibody response against B. pseudomallei 11 days after infection revealed a significantly higher immunoglobulin G2A (IgG2a)/IgG1 ratio in C57BL/6 mice than in BALB/c mice, indicating that a T helper type 1 immune response is associated with resistance to
infection with B. pseudomallei.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Characterization of a Murine Model of Melioidosis:
Comparison of Different Strains of Mice
*
Corresponding author. Mailing address: Medical
Microbiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany. Phone: 0511-532-4352. Fax: 0511-532-4366. E-mail:
Steinmetz.Ivo{at}mh.hannover.de.
Infection and Immunity, June 1999, p. 2891-2900, Vol. 67, No. 6
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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