Routine testing and empirical treatment for atypical bacterial co-infections may offer limited value in patients hospitalized with viral respiratory infections, according to a large retrospective cohort study from Denmark.
The study evaluated nearly 20,000 patients admitted with coronavirus disease 2019, influenza A or B, or respiratory syncytial virus, and found that confirmed co-infection with atypical bacteria was rare. Among patients tested for atypical pathogens, 21 had a positive result—about 1% of those tested—suggesting that routine diagnostic testing and empirical macrolide therapy may not be warranted for most patients in this setting.
The researchers analyzed data from 19,651 patients admitted to hospitals in the Central Denmark Region from February 2019 to February 2024. Patients were included if they had a positive test for severe acute respiratory syndrome coronavirus 2, influenza A or B, or respiratory syncytial virus from 24 hours prior to admission through 48 hours following admission.
The study assessed how often patients were tested for atypical bacteria—including Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydia species—and how frequently they received empirical clarithromycin. Overall, 2,369 patients (about 12%) underwent testing for Legionella and/or Mycoplasma. Among those tested, seven patients tested positive for L pneumophila and 14 tested positive for M pneumoniae. Testing for Chlamydia pneumoniae or Chlamydia psittaci was performed in 180 patients, and all results were negative.
Despite the low prevalence of confirmed atypical bacterial co-infection, 859 patients (4%) received empirical clarithromycin within 48 hours of admission. Most patients with confirmed atypical bacterial co-infection did not receive early macrolide therapy: 17 of 21 patients with a positive result did not receive clarithromycin prior to test results becoming available, and they did not receive other empirical antibiotics with atypical coverage.
Testing and empirical clarithromycin use were associated with year, age, and markers of more severe disease presentation, and testing frequency varied by hospital.
Patients with atypical bacterial co-infection had a lower median age than those who tested negative, while leukocyte count and C-reactive protein levels did not differ meaningfully between groups. Because of the low number of positive cases, the researchers did not further characterize distinguishing clinical features.
The researchers noted that diagnostic testing for atypical bacterial co-infections and empirical clarithromycin are not addressed in Danish or international guidelines for viral respiratory tract infections, and suggested the practice may be influenced by guidance for community-acquired pneumonia, in which macrolides are recommended for severe disease.
The study was led by Bo Langhoff Hønge, MD, of Aarhus University Hospital, and colleagues. The researchers concluded that their findings do not support routine testing for atypical bacterial co-infection or routine empirical treatment for atypical pneumonia in patients hospitalized with these viral respiratory infections. They noted exceptions may include patients who are severely ill, have an abnormal course of illness, have a history of exposure to atypical bacteria, or are admitted during an epidemic wave of Mycoplasma pneumoniae.
The researchers declared no competing interests.
Source: European Journal of Clinical Microbiology & Infectious Diseases
