ANTIBIOTICS IN FEED AID DEADLY BACTERIA: STUDY A study of salmonella poisoning has uncovered new evidence that the common practice of feeding antibiotics to cattle is helping to create deadly bacteria that can infect humans and resist medicines. Researchers at the federal Centers for Disease Control tracked the spread of an unusual strain of salmonella that is resistant to the drug chloramphenicol and were able to link the resulting food poisoning to farms that used the drug to promote the growth of cattle. Cattlemen often give their animals a constant supply of antibiotics in feed to help them grow faster. But critics have been warning for years that the constant exposure to the drugs is helping bacteria learn to resist the drugs. Industry officials have disputed this, saying the diseases that develop a resistance in cattle probably do not affect humans. But the new study, reported in Thursday's New England Journal of Medicine, shows the diseases can spread to humans. The research team, led by Dr. John Spika, said the number of people who have developed the chloramphenicol-resistant infection in Los Angeles County alone jumped from 69 in 1984 to 298 the following year. Two of those victims died and half the victims in their study of 45 patients had to be hospitalized for their illness. They also discovered that cooking the meat didn't always prevent the disease. Only 15 pct of the victims reported eating raw, infected hamburger. Thus, the researchers concluded, "the majority of cases appear to have been caused by eating hamburger that was at least partially cooked." The researchers said the results show that "food animals are a major source of antimicrobial-resistant salmonella infections in humans, and that these infections are associated with (antibiotic) use on farms."