Doxycycline for Treatment of Pneumococcal Infection Could Reduce Clostridioides difficile Infection


Less than 1% of individuals developed Clostridioides difficile infection (CDI), but for those who previously had a CDI the year before, 12% developed a new infection.

The use of doxycycline could protect against Clostridioides difficile infection (CDI) for some patients with pneumonia, according to results of a study published in the American journal of Infection Control.1 The study authors said that for those hospitalized with community-acquired pneumonia and who experienced a CDI in the prior year, doxycycline reduced the development of new CDI by 45% compared to azithromycin (Zithromax, ZPAK; Pfizer).1

Bacterial pneumonia, rod-shaped bacteria inside alveoli of the lung | Image Credit: Dr_Microbe -

Dr_Microbe -

“Our analysis found that in patients with a prior history of C. difficile, doxycycline was the only factor associated with a reduction in the incidence of new [CDI],” Kari A. Mergenhagen, PharmD, BCPS, BCIDP, residency director for infectious diseases at the Veterans Affairs of Western New York Healthcare System, said in a statement. “These results suggest that in cases where Legionella pneumonia can be ruled out prior to treatment, patients at increased risk of C. difficile may benefit from the use of doxycycline as a first-line agent.”1

In the study, investigators analyzed the outcomes of 156,107 individuals treated for pneumonia at Veterans Affairs Hospitals from January 2009 and August 2022. The investigators noted that due to the hospitals' demographic factors, patients were predominantly White, male, and elderly.1

The investigators included patients who had been admitted for no more than 48 hours before the pneumonia diagnosis was confirmed, helping them establish that all cases were community acquired, and not from the hospital setting.1

The individuals who were diagnosed with Legionella pneumonia or viral pneumonia were excluded due to the recommendations of treatment. For patients with CDI within 30 days of antibiotic treatment, investigators presumed it was associated with antibiotic use. Approximately 87% of individuals were treated with azithromycin and 13% were treated with doxycycline.1

Investigators found that less than 1% of individuals developed CDI, but out of those who previously had a CDI the year before, 12% developed a new CDI infection due to antibiotic treatment. For those who had a prior CDI, doxycycline was associated with a reduction of CDI from antibiotic usage. Among those without a history of CDI, there was no statistical difference in the rate of CDI between the different antibiotics, according to the press release.1

“Health care facilities have a keen interest in reducing the incidence of dangerous and costly healthcare-associated [CDI],” Patricia Jackson, RN, BSN, MA, CIC, FAPIC, 2023 president of APIC, said in the statement. “This study shows that for patients with a history of C. diff antibiotic choice is an important factor in decreasing these types of infections.”1


  1. Alternative antibiotic selection can reduce the risk of healthcare-associated infections for patients with pneumonia. News release. EurekAlert. November 2, 2023. Accessed December 14, 2023.
  2. O'Leary AL, Chan AK, Wattengel BA, Xu J, Mergenhagen KA. Impact of doxycycline on Clostridioides difficile infection in patients hospitalized with community-acquired pneumonia. Am J Infect Control. Published online November 2, 2023. doi:10.1016/j.ajic.2023.09.007
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