Abstract

A series of experiments involving Listeria monocytogenes was undertaken to study first the fecal shedding of Listeria by conventional mice challenged intraperitoneally with Listeria and second the fecal shedding and ability to survive of germ free mice with similar challenge. In addition, mites infesting Listeria infected mice were cultured for their possible contamination by Listeria.

Conventional mice were challenged intraperitoneally with a single near LD50 dose of Listeria. Fecal Listeria were detected by collecting specimens from each mouse daily for the first 4 days and every second day thereafter. The feces was held at 7°C for 14 days in Difco tryptose broth with polymyxin, subcultured to tryptose agar or if the specimen was found to contain interferring Proteus, the subculture was made to McBride agar. However, Listeria was found to grow more slowly on McBride agar.

Experiments indicated that as few as 26 Listeria bacilli mixed with 2 mouse fecal pellets could be detected by the above method.

Challenged mice began to shed Listeria as early as 2 hours after inoculation. Surviving, healthy appearing mice continued to shed the organisms 4 to 14 days before becoming apparently negative. However, several mice again began to shed Listeria as long as 42 days after challenge: Listeria was found in large numbers in livers, spleens, blood, and brains in mice that had died. However, it was found only in the livers of apparently healthy sacrificed mice autopsied 40 - 90 days after challenge.

To determine the effect of stress on the apparently healthy carrier state, 21 days after the last Listeria isolation, 7 survivors were given large doses of glucocorticoids. Three of the 7 mice again shed Listeria in the feces; 6 eventually died and only one survived without becoming a shedder again. Autopsy cultures of the mice which died indicated massive numbers of Listeria in blood and livers. The surviving mouse was apparently Listeria free.

Experiments indicated that a calculated dose of 8.5 x 102 but not 4.2 x 102 Listeria bacilli inoculated into mice under heavy glucocorticoid stress was lethal.

Three groups of germ free mice were housed together; one group was inoculated with a dose of Listeria calculated to be near the LD50 for conventional mice; a second was inoculated with 1/100 of this dose; a third group was not inoculated.

The death rate of those inoculated with the near LD50 was the same as that expected for conventional mice. The death rate of those receiving 1/100 of this dose was also the same. No deaths occurred among those not inoculated. All three groups of mice began shedding Listeria in the feces at the same time. Thus the non-inoculated mice acquired the infection rapidly from inoculated animals by oral or respiratory means.

Differences between reactions in the conventional and germ free mice were apparent. The organisms were not isolated from the feces of the germ free as early as they were isolated from conventional mice. Listeria was detected in the conventional mice as early as 2 hours after challenge; whereas they were detected in germ free mice only after 4 days. After Listeria was detected in the germ free mice the number shed remained remarkably high and uniform throughout the 22 days of the experiment, whereas in conventional mice the cultures were often negative after day 6.

Mites which were found feeding on Listeria challenged mice, were placed in a tube of tryptose-polymyxin broth to culture surface Listeria, if present, and then removed and transferred to a second tube of tryptose-polymyxin broth and crushed. Both tubes were held at 7°C for 14 days and subcultured to tryptose agar. Listeria were apparently present only in the internal organs of the mites since a pure culture of Listeria was obtained from the tube in which mites were crushed but no Listeria were obtained from the tube in which they were rinsed.

LLU Discipline

Microbiology

Department

Microbiology

School

Graduate School

First Advisor

Charles E. Winter

Second Advisor

Donald M. Brown

Third Advisor

Walter E. Roop

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1966

Date (Title Page)

9-1966

Language

English

Library of Congress/MESH Subject Headings

Listeria Monocytogenes

Type

Thesis

Page Count

vii; 77

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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