Dysbiosis is “qualitative and quantitative changes in the intestinal flora, their metabolic activity and their local distribution.”3
A number of factors can contribute to dysbiosis including3
- Stress (psychological and physical)
- Changes in diet
- Problems with peristalsis in the gastrointestinal tract
- Exposure to radiation
Antibiotics are a primary cause of dysbiosis and its adverse consequences, but the risk of dysbiosis is higher with some antibiotics based upon:3
- Spectrum of activity – the risk is higher with broad spectrum antibiotics relative narrow spectrums of activity.
- Dose and duration – generally, the longer duration and higher dose of antibiotic, the higher the risk of dysbiosis.
Adverse effects can occur with exposure to an antibiotic that impacts the microbiota. Adverse effects arise from several different mechanisms:7
- The reduction of key bacteria, including Bacteroidetes and Firmicutes.7
- Overgrowth of antibiotic tolerant or resistant microorganisms already present in the gastrointestinal tract, including fungi or C. difficile.7
- Increased susceptibility to intestinal pathogens. This is related to a decrease in colonization resistance due to disruption of the microflora barrier.7
- A reduction in the microorganisms that break down indigestible carbohydrates, which can lead to diarrhea and possibly electrolyte imbalances.4
The microbiota generally recovers to a near pre-treatment state within one week to two months after taking an antibioitic.8,9
However, there is some evidence that exposure to antibiotics can produce a longer-term impact on the microbiota, possibly lasting years.
Disruption of microbiota diversity may contribute to the development of5,6
- Gastrointestinal disorders (inflammatory bowel disease and irritable bowel syndrome)
- Stress-related psychiatric disorders