Influence of bile acids on rat gut microflora deterioration induced by oral ampicillin treatment

Abstract

Background: Metabolic capacity of gut microflora is huge and this "microb" organ can be considered as second biggest metabolic organ in body. The potential for an antibiotic to influence gut microflora is related to its spectrum of activity, pharmacokinetics, dosage and length of administration. In terms of pharmacokinetics, the rate of intestinal absorption plays a fundamental role. Apart from basic physiological functions, bile acids and their analogues are recognized as transport promoters for other substances, in potentiating their action. The aim of this study was to demonstrate potential protective effect of monoketocholic bile acid on rat intestinal microflora from oral ampicillin. Materials, Methods & Results: Eighteen Wistar rats were divided into three groups (n = 6). The experimental protocol was approved by Ethics Committee on Animal Use of the University Novi Sad. All animals received 10 mL/kg of body weight of drugs solutions per os by oral intubations. The animals have been treated twice daily for three days, with saline, ampicillin 500 mg/kg and ampicillin 500 mg/kg + monoketocholic bile acid (MKH) 4 mg/kg. The fecal pellets were collected twice, before and after the treatment was completed. Within 2 h of collection, samples of whole pellets were processed microbiologically. Weighed portions of feces were suspended 1:10 in sterile 0.9% NaCl and further diluted with same solutions up to 1: 10¹³. The number of colony forming units (CFU) was determined by direct counting. Only the plates containing 30 to 300 CFU were considered as valid. The ampicillin treated group, showed significant reduction of CFU number compared to value before treatment under aerobic (P = 0.019) and anaerobic (P = 0.00) conditions. Concomitant use of ampicillin and MKH did not show statisticaly significant reduction (P > 0.05) of CFU number compared to value before treatment in both cultivation conditions. There is significant reduction of CFU number (P = 0.02) only in group treated with ampicillin comparing to control group under the aerobic condition. Statistical analysis was performed by single test ANOVA and Kruskal-Wallis test with Monte Carlo exact test to test significant differences in CFU reduction between groups. Paired two-tailed t-test was performed on the log-transformed data of the CFU/g fecal sample to test for significant differences between counts before and after treatments inside the group. Discussion: Oral antibiotic applications can change the composition of normal gut microflora. Modification of normal microflora can change metabolism of many compounds. Longer local retention of ampicillin in the gut, due to poor absorption of antibiotic has led to a significant reduction in the number of intestinal microorganisms. Although the fecal flora does not exactly represent the gut flora, comparison of number of CFU from feces specimen before and after antibiotic treatment indirectly reflects the effect of the antibiotic on the bacteria in the gut. Co-administration of ampicillin and MKH, due to promoting effect of bile acid on to absorption of ampicillin, led to less disruption of CFU than in ampicillin group. Based on these results, it is concluded that concomitant use of ampicillin and MKH, could be useful for reducing the harmful effects of ampicillin on the intestinal flora. These results are consistent with the results obtained in pharmacokinetics study with the same substances.