The Fecal Flora of Various Strains of Mice. Its Bearing on Their Susceptibility to Endotoxin

Abstract

Adult mice from seven different colonies were studied with regard to (a) the numbers and types of bacteria that could be cultivated from their stools; (b) their resistance to the lethal effect of endotoxins prepared from three strains of Gram-negative bacilli. See PDF for Structure In six of the seven colonies, the stools yielded large numbers of various types of lactobacilli, enterococci, and Gram-negative bacilli. Most animals in these colonies died within 48 hours following injection of endotoxin. The other mouse colony (NCS) has been maintained for the past three years at the Rockefeller Institute under exacting sanitary conditions; it is free of many types of common mouse pathogens. The stool flora of NCS mice yielded very large numbers of viable lactobacilli (109 per gm), representing at least three different morphological types. In contrast, it contained only few enterococci and Gram-negative bacilli (less than 106 per gm). Moreover, E. coli, Proteus sp., and Pseudomonas sp. could not be recovered from the stools under normal conditions. NCS mice proved resistant to the lethal effect of endotoxins. These characteristics of the NCS colony prevailed whether the animals were housed continuously in individual cages on wire grids, or grouped continuously in large cages with wood shavings as litter. However, the composition of the bacterial flora could be rapidly and profoundly altered by a variety of unrelated disturbances such as sudden changes in environmental temperature, crowding in cages, handling of the animals, administration of antibacterial drugs, etc. The first effect of the change was a marked decrease in the numbers of lactobacilli and commonly an increase in the numbers of Gram-negative bacilli and enterococci. When tested 3 weeks after these disturbances some NCS animals were found to have become susceptible to the lethal effects of endotoxin.

Distribution of Indigenous Lactobacilli in the Digestive Tract of Conventional and Gnotobiotic Rats

“…It was confirmed that the indigenous lactobacilli, which could be classified into three species, colonized in different locations in the digestive tracts of rats. The intestinal microflora of rats may be influenced by various factors such as diet, environmental temperature, animal strain and stress, as several workers have observed in mice (2,6,13,15). Therefore, the experimental results cannot be generally applied to all of rats which might have different characteristics.…”

Stressor Exposure Disrupts Commensal Microbial Populations in the Intestines and Leads to Increased Colonization by Citrobacter rodentium

“…Exposure to stressors has been shown to significantly change microbial populations in the gastrointestinal tract of both humans and laboratory animals (4,5,20,28,34,36,48). For example, the stress response to maternal separation causes a significant reduction in lactobacillus levels in young monkeys (4).…”

Enhanced Toxicity for Mice of Vincristine and Other Chemotherapeutic Agents with Salmonella typhosa Endotoxin and Pseudomonas aeruginosa

“…The capability of live and heat-killed Escherichia coli cells to substitute for bacterial endotoxin in the lethal synergy involving actinomycin D has been demonstrated (11). Because Pseudomonas is a component of the normal flora of some strains of mice (12) and because of the increasing incidence of Pseudomonas infections in cancer patients (14), the capability of this bacterium to enhance the lethality of vincristine for mice was tested. Additional studies were undertaken to define the nature of the vincristine-endotoxin synergy.…”