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Antibiotic therapy with extended anaerobic coverage (EAC) was not associated with a survival benefit in patients with community-acquired aspiration pneumonia, according to results from a retrospective cohort study that support current guidelines.

Across 18 hospitals in Canada, in-hospital mortality rates were 30.3% for patients treated with antibiotic therapy with limited anaerobic coverage (LAC) and 32.1% for those treated with EAC, rates that were statistically no different after adjustment, reported Anthony Bai, MD, MSc, of Queen's University in Kingston, Ontario, and coauthors in .

EAC antibiotics were in fact associated with more harm than good: Clostridioides difficile colitis was seen in 0.2% or less of the LAC patient population and 0.8-1.1% of the EAC population, a 1% risk difference after adjustment (95% CI 0.3-1.7).

The present study supports skipping anaerobic coverage for aspiration pneumonia and relying on ceftriaxone or levofloxacin alone, Bai and colleagues concluded. They noted that the findings from their relatively large study, counting nearly 4,000 people, are consistent with previous studies while specifically including only patients receiving first-line antibiotics.

"Hopefully, this study will promote further adoption of the most recent guidelines relating to aspiration pneumonia, with resultant improvement in patient care, specifically decreased risk of side effects (C. difficile colitis), and potentially decreased antibiotic resistance in the community," commented Mark Yoder, MD, of Rush University Medical Center in Chicago, who was not involved in the research.

In 2019, despite the absence of strong trial-level evidence, the American Thoracic Society and Infectious Diseases Society of America released guidelines that to patients with aspiration pneumonia. The guidelines instead endorsed first-line antibiotics, like ceftriaxone or levofloxacin, for general treatment of patients with community-acquired pneumonia (CAP).

Indeed, the Canadian study showed a steady increase of aspiration pneumonia patients getting LAC antibiotics from 2015 to 2021.

"We have generally changed our practice accordingly and recommended against routine anaerobic coverage for CAP due to the risks of C. difficile infection and the need to avoid unnecessarily broad antibiotic use," said Rebekah Moehring, MD, MPH, of Duke University in Durham, North Carolina, who was not involved in the study. "We routinely face antibiotic resistance scenarios in our practice and thus a lot of emphasis has been placed on judicious use of antibiotics."

The study authors noted that antibiotic coverage for aspiration pneumonia "has been debated and changed over time" and that historically, anaerobic bacteria were thought to be the predominant pathogen.

Yoder and Bai's group both emphasized that anaerobic bacteria are isolated in only a minority of cases of aspiration pneumonia nowadays.

"Conceptually, almost all cases of pneumonia are due to aspiration of bacteria colonizing the oropharynx (mouth and throat), and the treatment of community-acquired as well as hospital-acquired and ventilator-associated pneumonia does not routinely include coverage of anaerobic pathogens," Yoder told MedPage Today via email.

The study included 3,999 consecutive adults hospitalized for aspiration pneumonia at 18 acute care hospitals in Ontario from 2015 to 2022. An ICD diagnosis code was used to search records of pneumonitis due to food and vomit including aspiration pneumonia not otherwise specified, or due to food, gastric secretions, milk, or vomit.

Bai and colleagues split participants into LAC (67.1%) and EAC (32.9%) groups based on the initial antibiotic they received within 2 days of admission. Ceftriaxone, cefotaxime, and levofloxacin counted as LAC; amoxicillin-clavulanate, moxifloxacin, metronidazole, and clindamycin were defined as EAC.

Baseline characteristics were well balanced between the two treatment groups. The patient population was approximately 40% women, and the average age was about 80 years old. Fewer than a fourth of patients were from long-term care facilities.

Among the most commonly used antibiotics were ceftriaxone, metronidazole, moxifloxacin, and macrolides.

Median length of stay was 6.7 days in the LAC group and 7.6 days in the EAC group. Among patients discharged alive, 18.5% of the LAC group and 18.3% of the EAC group were readmitted to the hospital within 30 days.

The investigators acknowledged that their database did not capture cases of aspiration pneumonitis that did not require antibiotic treatment. Other study limitations included the inability to count deaths or any C. difficile colitis diagnoses after hospital discharge.

"The avoidance of unnecessary antibiotic can decrease the risk of antibiotic adverse effects, especially C. difficile colitis," Bai's team nonetheless noted. "On a larger scale, limiting unnecessary antibiotic use may lower antibiotic selective pressure and result in less antibiotic resistance. In hospitals, antimicrobial stewardship programs can implement targeted interventions to de-escalate antibiotic therapy for aspiration pneumonia."

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