Effects of Antibiotics on Resistance to Colonization with Enteric Pathogens in Mice
There is considerable evidence that the administration of large quantities of antibiotics to experimental animals greatly increases their susceptibility to colonization with exogenous organisms. When the antibiotics are given perorally, the intestinal flora is frequently disrupted and the animals are easily colonized with enteric pathogens. This was demonstrated some time ago by Freter [3, 4], who gave Swiss mice and guinea pigs high concentrations of antibiotics, rendering the animals susceptible to infection with antibiotic-resistant strains of Shigella flexneri and Vibrio cholerae. At about the same time, Bohnhoff et al.  reported that peroral administration of streptomycin to mice greatly increased their susceptibility to Salmonella enteritidis infection. The antibiotic lowered the ID50 of Salmonella enteritidis from 1 million viable bacteria to fewer than 10 bacteria . Data from in vitro studies indicated that disruption of the flora resulted in a decrease in volatile fatty concentrations and an increase in the pH of intestinal contents, providing conditions that favored multiplication of Salmonella enteritidis.
KeywordsIntestinal Tract Intestinal Flora Antibiotic Administration Enteric Pathogen Streptomycin Sulfate
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