Alternative antibiotic for pneumonia may reduce risk of C. diff infection

A new study on Clostridioides difficile infections finds that choosing an alternative antibiotic for high-risk patients with pneumonia can reduce infection risk.

C. diff infections can be deadly, and they are often acquired by hospitalized patients taking broad-spectrum antibiotics.

More than 450,000 C. diff infections are reported in the United States each year, leading to as many as 30,000 deaths, according to public health estimates.

More than a third of patients who have a C. diff infection will go on to have another one in the future.

Pneumonia is common and typically treated with broad-spectrum antibiotics, so hospitalized patients with pneumonia are at increased risk for developing a C. diff infection.

The study, by U.S. Veterans Affairs researchers and published Thursday in the American Journal of Infection Control, found a 45% reduction in C. diff infections among high-risk patients when the antibiotic doxycycline was used instead of azithromycin. These high-risk patients were hospitalized with community-acquired pneumonia and had experienced C. diff infections in the prior year.

Clinical guidelines typically recommend azithromycin for these patients because it penetrates lung tissue and can successfully treat Legionella pneumonia and more common types of pneumonia.

Doxycycline should not be used to treat Legionella pneumonia, but it can be effective against other types of pneumonia.

It also has optimal absorption in the upper gastrointestinal tract with minimal impact on the gut microbiome. This could account for the reduced risk of C. diff infection, according to the study.

Researchers analyzed outcomes of more than 156,000 patients treated for pneumonia in U.S. Veterans Affairs Hospitals between January 2009 and August 2022.

Patients had to be admitted to the hospital no more than 48 hours before a pneumonia diagnosis to ensure that all cases were considered community-acquired pneumonia. Those diagnosed with Legionella pneumonia or viral pneumonia were excluded from the study.

Any patient who was diagnosed with a C. diff infection within 30 days of antibiotic treatment was presumed to have antibiotic-associated C. diff.

About 87% of patients were treated with azithromycin, while nearly 13% received doxycycline.

Fewer than 1% of patients developed C. diff infections, but among patients who had experienced a C. diff infection in the year before their pneumonia diagnosis, 12% developed a new C. diff infection associated with the antibiotic treatment.

In patients with no history of C. diff infections, there was no statistical difference in the rate of C. diff infections between those who received azithromycin and those who received doxycycline.

Where the authors did see a difference was in patients who had a C. diff infection in the prior year.

“Our analysis found that in patients with a prior history of C. diff, doxycycline was the only factor associated with a reduction in the incidence of new C. diff infections,” said senior study author Kari Mergenhagen, residency director for infectious diseases at the Veterans Affairs of Western New York Healthcare System.

“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,” Mergenhagen said in a journal news release.

The patients were predominantly male, elderly and white. Additional studies will be needed to determine whether these results would hold true for other patient populations.

“Healthcare facilities have a keen interest in reducing the incidence of dangerous and costly healthcare-associated C. diff infections,” Patricia Jackson, president of the Association for Professionals in Infection Control and Epidemiology (APIC), said in the release. “This study shows that for patients with a history of C diff, antibiotic choice is an important factor in decreasing these types of infections.”

More information

The U.S. Centers for Disease Control and Prevention has more on C. diff.

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