ABSTRACT
AIMS: To determine the effect of diet acidification and an in-feed antibiotic growth promotant (Tylosin, Ty) on selected culturable bacterial populations in the gastrointestinal tract (GIT) of mice. METHODS AND RESULTS: Female C57Bl mice were given a standard diet supplemented with Acid Pak (AP) or Ty in the drinking water. After 21 days, lumen and adherent populations of Enterobacteriaceae, enterococci/streptococci, and lactic acid bacteria (LAB) from the ileum, caecum, colon and faeces were enumerated. General intestinal health was assessed by the frequency of haemolytic bacteria in the different intestinal compartments. Contrary to expectations, AP and Ty significantly increased haemolytic bacteria in the lumen of the caecum and colon (P<0.05). The small but significant growth-enhancing effect of Ty (P<0.05) was associated with decreases in enterococci/streptococci and surprisingly, LAB, as well as increases in coliforms. AP, which failed to improve growth rates, reduced coliforms, had limited effects on enterococci/streptococci, and specifically failed to promote the growth of LAB populations in all intestinal compartments. Ty supplementation was also associated with a significant increase in macrolide-resistant enterococci throughout the GIT. CONCLUSIONS: Dietary acidification is less effective than Ty in modulating the population dynamics of selected culturable populations of enteric bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: The mouse can provide a useful experimental model to examine the effects of new dietary supplements, formulations or regimes on changes in microbial population dynamics, including monitoring for antibiotic resistance.
Subject(s)
Anti-Bacterial Agents/pharmacology , Gastrointestinal Tract/microbiology , Probiotics/pharmacology , Tylosin/pharmacology , Animals , Anti-Bacterial Agents/administration & dosage , Colony Count, Microbial , Diet , Dietary Supplements , Drug Resistance, Bacterial , Enterobacteriaceae/drug effects , Enterobacteriaceae/isolation & purification , Feces/microbiology , Female , Hydrogen-Ion Concentration , Mice , Mice, Inbred C57BL , Probiotics/administration & dosage , Streptococcaceae/drug effects , Streptococcaceae/isolation & purification , Tylosin/administration & dosageABSTRACT
A mouse model of Helicobacter infection of the gastric mucosa was evaluated for in vivo screening of new anti-Helicobacter pylori therapies. The aim of the study was to test antimicrobial agents with known anti-H. pylori effects in humans to validate that similar results were obtained in the mouse model. Specific pathogen-free mice were colonized with H. felis, a cat stomach isolate that has been shown to induce chronic gastritis in gnotobiotic mice. In H. felis-inoculated mice 4 weeks after treatment, only 25% were cleared with erythromycin, 47% with metronidazole, 0% with tetracycline, 70% with amoxycillin, and 25% with bismuth subcitrate. In contrast, triple therapy with metronidazole, amoxycillin, and bismuth subcitrate resulted in 80% eradication, whereas triple therapy with metronidazole, tetracycline, and bismuth subcitrate eradicated the Helicobacter from all the animals. We believe the similarities of these treatments to those reported in the literature for humans warrant the use of this model for the early screening of possible anti-H. pylori therapies, especially as in vitro testing has been found to be so non-predictive of therapeutic success.
Subject(s)
Anti-Bacterial Agents/therapeutic use , Disease Models, Animal , Drug Evaluation, Preclinical/methods , Duodenal Ulcer/complications , Helicobacter Infections/drug therapy , Helicobacter pylori , Animals , Anti-Bacterial Agents/administration & dosage , Drug Evaluation, Preclinical/standards , Evaluation Studies as Topic , Female , Helicobacter Infections/complications , Helicobacter Infections/transmission , Male , Mice , Microbial Sensitivity Tests , RecurrenceABSTRACT
A simple and easily accessible cockroach nerve preparation is described. Afferent potentials elicited by electric stimulation of the cercus showed remarkable stability, providing a fairly adequate background for pharmacological experimentation. Type I and type II pyrethroids were tested on the nerve preparation, and the results were compared with toxicity data obtained on the same species. Blockade of nerve conduction showed positive correlation (r = 0.804) with lethal effects. The preparation would be useful for determining neuronal point of attack of test compounds and the study of pyrethroids.