Modulation of the host flora.

Modulation of the bacterial flora of patients with a high risk of acquiring an infection can be achieved in several ways. The approach used in the Leiden University Hospital is based on selective elimination of the aerobic bacteria in the oropharyngeal cavity and intestinal tract, leaving the anaerobic flora intact. This kind of selective modulation of the host flora has an advantage in that it does not affect the colonization resistance provided by bacterial antagonism, which prevents colonization by resistant but potentially pathogenic bacteria or fungi. The elimination of aerobic bacteria combined with nursing in protective isolation and consumption of food with few bacteria has led to a significant reduction of the incidence of major and fatal infections in patients during episodes of severe granulocytopenia. From these results it may be concluded that the objective of selective antibiotic modulation, namely, the prevention of infections, can be achieved with this approach.