WASHINGTON — The Senate voted Wednesday not to allow the food-service industry to reassign AIDS-infected workers unless government scientists determine the disease can be transmitted through food.

The 99-1 vote on a measure supported by Sen. Orrin Hatch, R-Utah, was a defeat for Sen. Jesse Helms, R-N.C., and represents a reversal of a Senate vote this spring on the Americans with Disabilities Act.

Helms had promoted a House-backed amendment that would have let restaurants, supermarkets and others reassign workers with any contagious disease, including AIDS, away from direct contact with food.

The amendment creates one of the few categories of people exempted from the civil rights bill’s broad protections. Others exempted include people with mental aberrations such as pyromania or compulsive gambling.