Effects of imipenem, cefotaxime and cotrimoxazole on aerobic microbial colonization of the digestive tract.

Superinfections originating from a digestive tract colonized by abnormally high concentrations of aerobic microorganisms as a result of impaired resistance to colonization (CR) may complicate antibiotic therapy. In this study, patients with a moderate to severe systemic infection were randomized to receive either cefotaxime (CTX, n = 10) or cotrimoxazole (CTR, n = 10), 2 antibiotic regimens presumed to spare CR; or imipenem/cilastine (I/C, n = 19). The effect on CR was measured indirectly by comparing the aerobic faecal flora before antibiotic treatment with that on day 8 of treatment.

Co-trimoxazole impairs colonization resistance in healthy volunteers.

The influence of co-trimoxazole on colonization resistance of the bowel was investigated in six healthy volunteers, by measuring the numbers of indigenous aerobic flora and of a co-trimoxazole resistant challenge strain of Klebsiella pneumoniae. Impairment of colonization resistance of the bowel was shown by a significant increase in the numbers of yeasts in the faeces of five of six volunteers, by a significant increase in the numbers of Gram-negative bacilli in the faeces of two of six volunteers, and by facilitation of colonization of the bowel by the challenge strain in all volunteers. Impairment of colonization resistance of the mouth was shown by the development of glossitis caused by Candida albicans in two volunteers, and by a significant increase in the numbers of yeasts in mouth washings from four volunteers.

Influence of pefloxacin on microbial colonization resistance in healthy volunteers.

The influence of pefloxacin, 400 mg twice daily for ten days, on microbial colonization resistance was investigated in six healthy volunteers. In three volunteers impairment of colonization resistance was indicated by a significant increase in the faecal concentration of yeasts. In two of them, impairment of colonization resistance was confirmed by facilitation of colonization by a challenge strain of Klebsiella pneumoniae in the early post-treatment period.