How's this for preventative medicine?: Ingesting bacteria may help to prevent infections.

Researchers at Creighton University School of Medicine in Omaha, Neb., recently demonstrated that regular doses of probiotic bacteria given to hospital patients on mechanical ventilators resulted in fewer cases of pneumonia. The findings were published online June 3 in the American Journal of Respiratory and Critical Care Medicine.

Probiotics, live microorganisms thought to provide a health benefit when consumed in sufficient amounts, are frequently used to mitigate a variety of conditions, including digestive disorders such as antibiotic-associated diarrhea, lactose intolerance and irritable bowel syndrome. Scientific evidence to back many claims, however, is often preliminary at best or lacking entirely. The new study demonstrates that one strain of so-called beneficial bacteria can prevent pneumonia in some patients, and may be useful for the prevention of hospital-acquired infections.

Lee Morrow, an associate professor of medicine at Creighton and lead author of the study, along with his colleagues administered a solution containing the human intestinal probiotic bacteria, Lactobacillus rhamnosus GG or a placebo to 138 critically ill patients on ventilators. The study was designed so that neither patients nor care providers knew which group received probiotics. The patients received treatment twice daily and were monitored routinely for the presence of pneumonia-causing pathogens. The researchers observed that probiotic treatment reduced the number of cases of pneumonia by nearly half.

"We chose to study probiotics in this context because ventilator-associated pneumonia (VAP) is increasingly caused by pathogens associated with antimicrobial resistance, and the supply of novel antibiotics is essentially nonexistent for the foreseeable future," Morrow said in a prepared statement.

Pneumonia affects nearly 30 percent of patients on ventilators; it can result when microorganisms from the mouth or ventilator equipment are inhaled into the lungs. In addition to causing health complications for individuals who are already critically ill, VAP results in higher health care costs.

"This is an enormous accomplishment," says Donald Craven, a physician at the Lahey Clinic Medical Center in Burlington, Mass., who was not involved in the study. The results "hold promise for trying to prevent an infection that has serious morbidity, mortality and is a major factor for hospital costs that we're trying to contain," he adds.

Patients receiving probiotics were also less likely to develop diarrhea caused by Clostridium difficile, a common bacterium found in health care venues, and required less antibiotic treatment when C. difficile infections occurred. No side effects were associated with either the placebo or probiotic treatment.

In support of the current findings, a recent systematic review of previous studies of the use of various probiotic strains suggested that probiotics may reduce VAP by 39 percent. The mechanism by which probiotics prevent pneumonia, however, remains unresolved. Some evidence suggests that probiotics may modulate the immune system to help it to ward off pathogens. Future studies will be necessary to identify the precise mechanism as well as the optimal dose and strain of probiotics for specific conditions.

Under certain circumstances probiotics can actually be harmful and cause secondary infections. The authors cautioned that their preliminary findings apply only to the carefully monitored study population, and should not be generalized to all hospital patients. Furthermore, the results need to be replicated by research at other care facilities, ideally using a diversity of patient populations.

Nevertheless, Morrow and colleagues suggest that probiotic treatment could be a novel, inexpensive, nonantibiotic approach to preventing secondary infections. Using Lactobacillus rhamnosus GG to prevent pneumonia "appears safe and efficacious in a select population of patients," the authors concluded.