[Choose preparations that affect the intestinal ecosystem as little as possible!].

The administration of antimicrobials often causes ecological disturbances in the normal microflora, such as decreased colonisation resistance which may result in overgrowth of potentially pathogenic micro-organisms such as yeasts and Clostridium difficile. Another possible consequence is the establishment of resistant strains which may spread within the host, or from person to person, causing infection. Resistant bacteria can also transfer resistance genes to their own or other species. The article consists in a review of studies performed by various investigators during the past 20 years, and illustrating the impact of different antimicrobial agents on the human gastrointestinal microflora.