Effects of six antimicrobial drugs on rat intestinal flora: is the rat model of predictive value in clinical practice?

The effects of six antimicrobial agents on rat intestinal microflora after oral and/or parenteral administration were studied in parallel. Antimicrobial drugs were administered by the oral (norfloxacin, pefloxacin, ciprofloxacin) and parenteral routes (pefloxacin, imipenem, aztreonam, teicoplanin) at the doses used in clinical practice. Faecal specimens were collected before and after two, four, seven or 11 treatments. Qualitative and quantitative determination of flora composition was performed using a modified version of standard methods. Fluoroquinolones reduced the levels of enterobacteria, while gram-positive bacteria (enterococci, staphylococci, lactobacilli) were little affected. Comparable effects were observed after intraperitoneal and oral administration of pefloxacin. The changes induced by fluoroquinolones on intestinal flora showed a uniform trend: certain differences may be ascribed to different pharmacokinetic properties such as bioavailability and metabolism. Imipenem caused a significant decrease in mean concentrations of E. coli, clostridia and fungi. Aztreonam induced a prompt and marked inhibition of E. coli and Proteus spp., while prolonged treatment induced an overgrowth of fungi and bacteroides. Teicoplanin caused a significant decrease in the levels of clostridia and anaerobic lactobacilli. Irregular concentrations of all drugs, with great intersubject variability, were detected at different times. These results are comparable to those observed in humans. The potential of an antimicrobial agent to change the intestinal microflora is related to its antibacterial activity, route of administration and pharmacokinetic properties. The parenteral route induced changes in the intestinal ecosystem, as did oral administration. The rat appears to be a useful experimental model for studying the effects of antimicrobial drugs on intestinal flora

Bacterial Faecal Flora in Healthy Women of Different Ages

The composition of the intestinal flora is the result of host physiology, microbial interaction and environmental influences. The possible relationship between faecal flora composition and hormonal modifications in healthy women of different ages was studied. Forty-four normal women were divided into the following groups according to age: group I, 2747 yr; group II, 50-55 yr, 5 yr after menopause. The subjects received no pharmacological treatment. Samples were collected on the 8th and 23rd day of the cycle; two samples were obtained from each postmenopausal woman. Qualitative and quantitative determination of microorganisms was carried out using slightly modified standard methods. In fertile women (group I), the microflora composition was similar for samples collected on the 8th-10th day and during the premenstrual period (23rd day). In postmenopausal women (group III), an increase in fungi, clostridia and aerobic lactobacilli mean concentrations were observed. Escherichia coli mean levels increased and Enterobacteriaceae such as Enterobacter cloacae and Citrobacter freundii were present in 80 per cent of subjects studied. The length of menopause was found to have only a slight influence on flora: the behaviour of the microflora composition in menopausal women in group II may be considered intermediate between groups I and III. This preliminary study demonstrates that there are fluctuations in the composition of the faecal flora in healthy women. The differences observed between premenopausal and postmenopausal women may be a consequence of modifications of the steroid sex hormone pattern.Keywords - Intestinal flora; Age; Premenopausal women; Postmenopausal women; Menopause

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