Study: Doxycycline can reduce recurrent C. diff infections in people with pneumonia

People with pneumonia who have experienced Clostridioides difficile (C. diff) infections may be able to reduce recurrences if they take doxycycline instead of the standard treatment. The study comes as the US Centers for Disease Control kicked off C. diff awareness month Wednesday.

The study was published today in the American Journal of Infection Control. Those who were hospitalized with community-acquired pneumonia who had experienced C. diff infections in the prior year had a 45% reduction in the development of new C. diff infections when they took doxycycline instead of azithromycin.

Estimates say there are more than 450,000 C. diff infections in the United States annually, and the infections lead to about 30,000 deaths each year. A C. diff infection comes with a high chance of recurrence; in fact, more than one-third of patients who develop a C. diff infection will have another in the future. Hospitalized people who have pneumonia have an increased risk for having a C. diff infection.

Researchers examined how 156,107 people fared when they were treated for pneumonia at Veterans Affairs hospitals between 2009 and 2002. People with Legionella pneumonia or viral pneumonia were excluded from the study, because the recommended treatment for these conditions is different compared to typical community-acquired pneumonia. 

Of the people with pneumonia, 87% were treated with azithromycin and 13% received doxycycline. Less than 1% of people came down with C. diff infections; but among those who had a C. diff infection in the year before being diagnosed with pneumonia, 12% developed a new C. diff infection after ceftriaxone plus either azithromycin or doxycycline. There wasn’t a difference in the rate of C. diff infections between those who received azithromycin and those who received doxycycline among people without a history for C. diff infections. People who had a C. diff infection in the prior year, using doxycycline was associated with a 45% reduction in antibiotic-associated C. diff infection compared to azithromycin.

Doctors typically use azithromycin, which works to treat Legionella pneumonia as well as more common types of pneumonia. Doxycycline should not be used solely to treat Legionella pneumonia, but it can work to treat other types of pneumonia. Doxycycline has optimal absorption in the upper gastrointestinal tract with minimal impact on the gut microbiome, which could show why people who take it are less prone to C. diff infection.

“These results suggest that in cases where Legionella pneumonia can be ruled out prior to treatment, patients at increased risk of C. diff may benefit from the use of doxycycline as a first-line agent,” Kari A. Mergenhagen, PharmD, residency director for infectious diseases at the Veterans Affairs of Western New York Healthcare System and senior author of the study, said in a statement.