Although bacterial diseases are the second leading cause of death worldwide, drug companies are developing too few new medicines to fight them. That's the conclusion of a new study in the journal Clinical Infectious Diseases.

The researchers found that approvals of new antibiotics by the U.S. Food and Drug Administration have declined nearly 60 percent in the last two decades and out of more than 500 new drugs currently under development at the world's largest drug companies, only six are antibiotics. Public health officials are especially concerned about the lack of new antibiotics because bacteria are developing resistance to existing drugs.

"We just have a situation where our free market society is not meeting a specific need," he said.

Study co-author John Edwards heads the infectious disease division at the Harbor UCLA Medical Center. He said that heart disease, arthritis, and diabetes are on the rise in the industrialized world's aging population. So drug companies are responding with new medicines for these chronic conditions and he added that there's an added incentive for developing these drugs, because patients take them for life, compared to antibiotics, which are only taken for a week or two.

"So, not only are there needs in the area of these more chronic diseases, but it's also much more profitable for a drug to be developed in those areas than it is for an anti-infective drug to be developed," he said.

Dr. Edwards added that the federal government may need to step in and provide incentives for drug companies to develop more antibiotics.