Scientists are warning that over-prescribing antibiotics for every sniffle and ear infection is fast helping germs mutate so the medicines no longer work when they are really needed.

Antibiotic resistance appears "to be on the verge of desperation," said Nobel laureate Joshua Lederberg, chairman of an Institute of Medicine panel that called Thursday for global efforts to fight the problem.Up to 40 percent of antibiotics prescribed for various respiratory and ear ailments are inappropriate, said microbiologist Gail Cassell, vice president of Eli Lilly & Co.

The issue is so pressing that the government and American Academy of Pediatrics have mailed every pediatrician new brochures to give parents, urging that they not demand drugs for every sniffle. The rate of antibiotic use in children under 15 is three times higher than for any other group.

"When your child is sick, antibiotics are not always the answer," say the brochures. They explain that antibiotics have no effect on viruses, which cause all colds and most sore throats, and are not always needed for ear infections.