SUNDAY, May 21, 2017 (HealthDay News) -- The first prescription of an antibiotic that the average U.S. adult with pneumonia receives is now ineffective in about a quarter of cases, a new study finds.
In these cases, more or different antibiotics were needed, or the patient's condition worsened to require ER admission or hospitalization within a month of the antibiotics being taken, the research team said.
The results are "concerning," because "pneumonia is the leading cause of death from infectious disease in the United States," said lead researcher Dr. James McKinnell, an infectious disease specialist at LA BioMed, a California-based research foundation.
Speaking in a news release from the American Thoracic Society, he added that, "the additional antibiotic therapy noted in the study increases the risk of antibiotic resistance and complications like C. difficile infection, which is difficult to treat and may be life-threatening, especially for older adults."
Infectious disease experts have sounded the alarm for years on the growing problem of antibiotic resistance -- germs mutating around these lifesaving drugs.
One expert who reviewed the new findings said they highlight that threat.
The fact that a quarter of pneumonia patients failed their initial antibiotic therapy, "could be related to change in the bacterial resistance in the community," said Dr. Bushra Mina, who directs the medical ICU at Lenox Hill Hospital in New York City. And he noted that with pneumonia, "a certain percentage" of cases are caused by viruses, for which antibiotics are useless.
In the new study, McKinnell's team tracked data from nearly 252,000 adults who were prescribed antibiotics to treat pneumonia contracted outside of a hospital ("community-acquired"). Patients were cared for at either a doctor's office or other outpatient facility.
Just over 22 percent of the patients did not respond to their initial prescription of antibiotic treatment, the study found.
"Our findings suggest that the community-acquired pneumonia treatment guidelines should be updated," McKinnell said. Any update should include data on what risk factors leave patients vulnerable to antibiotic failure, he added.
According to their new findings, one key risk factor is age.
"Patients over the age of 65 were nearly twice as likely to be hospitalized compared to younger patients" after adjusting for other risk factors, McKinnell said. Because of this, "elderly patients are more vulnerable and should be treated more carefully, potentially with more aggressive antibiotic therapy."
Two other experts in pulmonary infections said the study did have its flaws, however.
Dr. Howard Selinger is chair of family medicine at Quinnipiac University's school of medicine in Hamden, Conn. He said the study was unclear on how the pneumonia diagnoses were made -- in many cases, what doctors thought was an antibiotic-responsive illness might have been viral bronchitis or other disease that antibiotics won't help.
For this reason, Selinger said, "I strongly doubt 25 percent resistance to multiple different classes of antibiotics." Instead, many of the cases in the study may have been viral to begin with, Selinger said.
Dr. Alan Mensch, a pulmonologist at Northwell Health's Plainview Hospital in Plainview, N.Y., agreed. He said that too few of the patients in the study had the "gold standard" sputum (phlegm) test that is needed to confirm a bacterial, not viral, infection.
But he said there is still much to learn from the findings. "Clearly, the current guidelines for community-acquired pneumonia published in 2007 by the American Thoracic Society and Infectious Disease Society of America need updating," Mensch said.
Any update should include protocols to better identify the cause of a pneumonia, and perhaps quicker hospital admission for elderly patients who haven't responded to drug therapy,' he said.
The study was slated to be presented on Sunday at the American Thoracic Society's annual meeting, in Washington, D.C. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
The American Lung Association has more on pneumonia.