Breast milk battles thrush in infants.

A mother's milk may be the best medicine for newborn infants with AIDS.

Human breast milk inhibits the growth of yeast spores, the source of a painful fungal infection of the mouth and throat in infants, according to research presented last week.

Called thrush, the infection affects approximately 5 percent of all newborns. Babies born with compromised immune systems are at much higher risk of developing thrush.

The yeast responsible, Candida albicans, is one of the leading sources of infection in pediatric AIDS, says Annalee S. Lucena of Miami University in Oxford, Ohio, who presented the work with her colleague Marcia R. Lee. The sprouting fungus burrows into soft tissue, forming white patches at the back of the throat. Nursing becomes painful and babies often stop feeding. "Once these babies have [thrush], there is very little chance of survival," says Lucena.

Normally a benign inhabitant of the body, the fungus is also responsible for vaginal yeast infections in adult women and diaper rash in infants. Babies commonly pick up the fungus in the birth canal. The yeast can reside harmlessly in moist folds of their skin. A healthy immune system usually keeps C. albicans in check.

Lucena added a yeast solution to diluted and full-strength breast milk. Without milk, yeast germinates within 2 days. Although the yeast stayed alive in the full-strength and diluted milk, even low dilutions of milk--down to 1 part in 750--inhibited yeast germination and growth.

Human breast milk contains antibodies that are absorbed by the baby's disgestive tract and help the young immune system recognize invaders. When Lucena removed the most abundant antibody, the milk's antifungal properties disappeared. Other tests indicated, however, that this antibody alone can't defeat the yeast.

Some antifungal medications can control thrush, but they're harmful and are only used as last resort, even in adults. With these powerful drugs, says Lucena, "the cliche is that you either kill the fungus or you kill the person." She contends that breast milk from a woman who does not have AIDS would be a good alternative or addition to the arsenal of antifungal drugs for thrush in infants.