Antibiotics are compounds that target bacteria and, thus, are intended to treat and prevent bacterial infections.
In a study from Michigan Medicine, scientists found a common clinical practice of antibiotics may be inadvertently harming patients.
They suggest that the administration of antibiotics with activity against anaerobic bacteria has a profound effect on the gut microbiome and, ultimately, an adverse impact on critically ill patients.
The research suggests that depleting the gut of these ‘good bugs’ may be contributing to worse clinical outcomes.
In the paper, the researchers conducted a retrospective single-center cohort study of 3,032 critically ill patients, comparing those who did and did not receive early anti-anaerobic antibiotics.
By comparing ICU outcomes in all patients, and changes in gut microbiota in 116 of the patients, they found that those who received anti-anaerobic antibiotics early in their hospital course had worse outcomes, whether measured in overall survival, infection-free survival, or pneumonia-free survival.
The results showed that antibiotics really can’t be considered a single entity, as they have widely different impacts on the microbiome and on the patients.
Patients who received anti-anaerobic antibiotics did far worse than patients who didn’t. The researchers suggest that which antibiotic is given probably matters more than how quickly they are administered.
The authors also found dramatic consequences of these antibiotics on the gut microbiome—during hospitalization, patients who received anti-anaerobic antibiotics had decreased initial gut bacterial density, followed by increased expansion and domination of the microbiome Enterobacteriaceae (a genus of common bacteria, many of which are pathogenic and cause opportunistic infections in immunocompromised hosts).
These findings confirm that anti-anaerobic antibiotics have a dramatic effect on gut bacterial communities.
While the primary findings were from an observational study in humans, the team confirmed the results using animal modeling.
In two different mouse models (pneumonia and oxygen-induced lung injury), animals who were treated with anti-anaerobic antibiotics did worse.
Anti-anaerobic antibiotics increased the susceptibility of mice to pneumonia due to Enterobacteriaceae and increased their mortality from oxygen toxicity.
Co-author Rishi Chanderraj, M.D., a Clinical Lecturer in Infectious Diseases at U-M, was the lead researcher on the initial project and will be carrying the work forward in future studies.
If you care about antibiotics, please read studies about antibiotics used in midlife linked to cognitive decline, and reach for the anti-inflammatories, not the antibiotics, for dental pain.
For more information about health, please see recent studies about the best time to take vitamins to prevent heart disease, and these antioxidants could help reduce dementia risk.
The study was conducted by Robert Dickson et al and published in the European Respiratory Journal.
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