MONDAY, March 26 (HealthDay News) -- Antibiotics can prolong cystic fibrosis patients' lives, but the drugs also help treatment-resistant bacteria thrive in their lungs, a new, small study suggests.

The findings from the 10-year investigation suggest, but do not prove, that the current standard of aggressive antibiotic treatment for cystic fibrosis patients may not always be the best approach.

It's common to use antibiotics to control infection in cystic fibrosis patients' lungs, but maintaining a more diverse range of bacteria in the lungs may help some patients stay healthy longer, according to study senior author Dr. John LiPuma, a research professor of pediatrics and communicable diseases at the University of Michigan Medical School in Ann Arbor.

"The conventional wisdom has been that as patients with cystic fibrosis age and become sicker, as their lung disease progresses, more and more bacteria move in," he said in a university news release. "But our study -- which was the first to examine the bacterial communities in cystic fibrosis patients' lungs over a long period of time -- indicates that's not what happens."

Aggressive use of antibiotics actually lowers the diversity of lung bacteria, resulting in infections that are increasingly difficult to treat. A more diverse community of lung bacteria may help keep the most dangerous strains in check, the researchers noted.

"What we normally do is essentially carpet bombing with antibiotics," explained LiPuma. "However, what we found is that over time this ultimately helps treatment-resistant bacteria by getting rid of their competition."

He said the findings may be a first step toward developing new treatment methods, such as more focused use of antibiotics or even giving cystic fibrosis patients beneficial bacteria.

The study was published March 26 in the Proceedings of the National Academy of Sciences.

Cystic fibrosis is a chronic disease in which the body produces thick, sticky mucus that clogs the lungs. The accumulation of the mucus leaves people prone to serious, hard-to-treat and recurrent infections. Eventually, the repeated infections destroy the lungs.

In the study, researchers examined the bacteria from six patients collected over eight to nine years. Half of the patients had a relatively stable type of the disease and the others had the more typical, faster-progressing form. The investigators conducted DNA analysis on bacteria in 126 sputum samples.

Over time, the researchers found that bacterial diversity declined, yet the overall level of bacteria remained fairly constant. The study authors explained that this means a small number of organisms multiply to take the place of those that have been killed off by antibiotics.

More information

The U.S. National Heart, Lung, and Blood Institute has more about cystic fibrosis.