INFLUENCE OF ROUTE OF INFECTION AND OTHER FACTORS ON GROWTH AND DISTRIBUTION OF LISTERIA MONOCYTOGENES IN ORGANS OF MICE
ARMY BIOLOGICAL LABS FREDERICK MD
Pagination or Media Count:
The growth of Listeria monocytogenes in the lungs, liver, spleen, brain, and blood of mice was observed after infection by the respiratory, intravenous, and intraperitoneal routes. The lungs of mice exposed to Listeria aerosols contained about 1,000,000 infected cells per ml within 24 hr, and the number of organisms remained high for at least 9 days. After exposure by the other two routes, fewer organisms appeared in the lungs. The colony counts of organisms in spleen and liver homogenates were similar regardless of the route. Organisms were found sporadically in the brain and blood. When a cell extract of Listeria was injected simultaneously with the organisms, greater numbers of Listeria were found in spleen and liver than when the bacteria were injected alone. On the other hand, the BCG strain of Mycobacterium tuberculosis enhanced the resistance of the mice, as shown by the recovery of fewer organisms from tissues when compared with tissues from mice receiving L. monocytogenes alone. Prior administration of BCG also reversed the effect of the Listeria extract. Mice 5 to 6 weeks old born of Listeria-infected mothers were infected with the homologous organism by the intraperitoneal route. Fewer organisms were recovered and the gross pathology was less extensive than in infected progeny of healthy females. However, there was no difference in the LT50 time to death for 50 of the animals between the two groups. In a similar experiment, using 7- to 8-week-old mice born of infected and healthy mothers, there was no difference in the bacterial counts, gross pathology, or LT50 between the two groups.