Repeated antibiotic exposure may be associated with severe COVID-19 outcomes, British researchers reported this week in eClinical Medicine.
To investigate whether frequent antibiotic exposure may be linked to COVID-19 severity, a team led by researchers from the University of Manchester conducted a matched case-control study of patients hospitalized for COVID-19 (the cases) and those with a COVID-19 diagnosis (the controls). Using 3 years of patient data prior to infection, the researchers created five quintile groups based on the number of prior antibiotic prescriptions and used conditional logistic regression to compare the difference between cases and controls.
Overall, 2.47 million COVID-19 patients were identified from February 1, 2020, to December 31, 2021. Of those, 98,420 were hospitalized, and 22,600 hospitalized COVID-19 patients died within 30 days of admission.
The researchers observed a dose-response relationship between the number of antibiotic prescriptions and the risk of severe outcomes. The case group had higher odds of receiving antibiotics than controls, and the risk rose with increased exposure. For the highest antibiotic exposure quintile, the adjusted odds ratio (OR) was 1.80 (95% confidence interval [CI], 1.75 to 1.84) for hospital admission and 1.34 (95% CI, 1.28 to 1.41) for death compared with patients without antibiotic exposure.
Larger number of prior antibiotic types was also associated with more severe COVID-19 outcome. The adjusted OR for those who received more than three antibiotic types in the previous 3 years was nearly double that of those who received only one antibiotic type (OR, 1.80; 95% CI, 1.75 to 1.84 vs OR, 1.03; 95% CI, 1.01 to 1.05).
It seems advisable to discourage the regular practice of indiscriminately prescribing antibiotics repeatedly and intermittently.
The authors say that while the results could be subject to potential confounding—eg, patients using antibiotics may have been immunocompromised and more likely to be hospitalized for COVID-19—a possible explanation is that repeated antibiotic exposure may have disrupted the gut microbiota in ways that led to adverse events or increased risk of secondary bacterial infection.
"Given the known effects of antibiotics on the gut microbiome, it seems advisable to discourage the regular practice of indiscriminately prescribing antibiotics repeatedly and intermittently, given their uncertain benefits and likely risks," they wrote.