IT IS well known that indiscriminate use of antibiotics or antimicrobial agents generally carries with it major risks. The reason why resistant microbes establish themselves in a population is simple. Every time one tries to eliminate a microbial infection, one is unwillingly carrying out an evolutionary lottery in which the winning numbers are carried by newly arising resistant forms. Because they survive and keep dividing, while the original, sensitive form is either killed or incapacitated, they soon take over the entire population.

The conventional response to the threat of drug resistance is to exercise prudence in the use of the drug. Drug resistance arises via genetic alteration, a mutation. The mutation helps the