WEDNESDAY, Jan. 19 (HealthDay News) -- Intensive care patients who may be infected with strains of pneumonia that are resistant to many drugs may be more likely to die if current treatment guidelines are followed, a new study suggests.

The findings highlight the need to reassess the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA) guidelines, said the researchers.

Current guidelines call for immediate antibiotic treatment -- before culture results are known -- of patients at risk for multiple drug-resistant (MDR) infection. The guidelines state that patients should receive a regimen of three antibiotics: two drugs against so-called Gram-negative pathogens and one drug against methicillin-resistant Staphylococcus aureus, or MRSA. The logic in this approach is that at least one drug should be active against any likely infectious agent.

However, several studies conducted since the guidelines were released in 2005 have failed to show that dual Gram-negative therapy is better than treatment with a single drug, the researchers noted.

For their study, a team led by Dr. Daniel Kett, of the University of Miami Miller School of Medicine, enrolled 303 patients at risk for MDR pneumonia from four academic medical centers in the United States. Of those patients, 129 were treated according to the ATS/IDSA guidelines and 174 received a different treatment.

The rate of survival after 28 days was 65 percent in the guidelines-compliant group and 79 percent in the group that didn't adhere to the guidelines, the investigators found.

"Our results further question the need for combination Gram-negative empirical treatment for patients with pneumonia, even those who are severely ill and at risk of multi-drug resistant pathogens," the researchers wrote.

One expert was not surprised by the findings.

"Who gets pneumonia with resistant bacteria? It is a person in such weakened condition that they are vulnerable to pathogens that would otherwise be trivial," noted Dr. Bruce Hirsch, attending physician in the infectious diseases division at North Shore University Hospital in Manhasset, N.Y. "It is a person who has suffered multiple infections already and has been exposed to multiple courses of antibiotics. It is a person with structural lung abnormalities that prevent the lungs from recovering from infections."

According to Hirsch, the new study "demonstrates high mortality rates in patients given recommended antibiotics as well as individualized antibiotics. Even in this age of sophisticated and powerful medications, adherence to the best guidelines can fail us."

For their part, the study authors "recommend that the planned, revised ATS-IDSA guidelines be reassessed before widespread implementation. Since the most common reason for non-compliance was failure to use a secondary anti-Gram-negative drug, we suggest a comparison of regimens employing MRSA treatment and single versus dual Gram-negative coverage."

The study was published in the Jan. 19 online edition of The Lancet Infectious Diseases.

More information

The American Lung Association has more about pneumonia.