Emergence of resistance as a consequence of antimicrobial prophylaxis in immunocompromised patients.

Many authors in the literature have investigated the use of antibiotics in prophylaxis against infections in granulocytopenic patients. Two general methods have been used: one consists in trying to decontaminate the digestive tract in the hope of reducing the amount of microorganisms responsible for systemic infections. Another method is to use well-absorbed oral antibiotics, like trimethoprim-sulphamethoxazole, throughout the neutropenic period. It is considered critical to preserve as much as possible of the anaerobic flora, which is believed to provide protection against colonization by aerobic microorganisms or by fungi. Experimental and clinical evidence for this is critically reviewed. The efficacy of such methods has been variable, but there is also widespread fears that they could enhance selection of resistant organisms. We have reviewed the literature, specifically looking for data on the emergence of such resistant organisms, as well as data on changes in bacterial and fungal faecal flora.