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The impact of antibiotics on the microbiome: a review of research and current scientific evidence
Microbiome The human gut is considered by modern science as one of the key regulators of metabolic, immune, and neurochemical processes. Recent studies show that the composition of the intestinal microbiota is directly related to resistance to infections, the effectiveness of the immune response, the speed of tissue repair, the response to drug therapy, and even cognitive functions.
Antibiotics, while remaining critically important in the treatment of bacterial infections, can also cause significant changes in the structure and diversity of the microbiome. These changes can be temporary or long-lasting, affecting the body for months and sometimes years. Scientific reviews by WHO and publications in the journals Nature Microbiology, Cell and Science Translational Medicine confirm that antibiotics are one of the most powerful factors modifying human bacterial ecosystems.
Systemic effects of antibiotics on the microbiome: summarizing the evidence
Broad-spectrum antibiotics significantly reduce bacterial diversity, especially the genera Bifidobacterium, Lactobacillus, Faecalibacterium, and Akkermansia, which play a key role in maintaining intestinal barrier function.
Mayo Clinic publications emphasize that the decrease in the number of these bacteria is associated with increased permeability of the intestinal wall, modification of the immune response, and impaired synthesis of short-chain fatty acids — critically important metabolites for intestinal cells.
Scientific evidence shows several universal effects of antibiotics:
• reduction of bacterial diversity
• change in proportions between dominant bacterial genera
• increase in the number of opportunistic pathogens
• inhibition of the synthesis of beneficial metabolites (SCFA, B vitamins, vitamin K2)
• risk of colonization with resistant strains of bacteria
Disruption of the microbiome after a course of antibiotics is described as «antibiotic-induced dysbiosis,» which can have clinical consequences.
The effect of different groups of antibiotics: a comparative analysis
Scientific observations demonstrate that the degree of effect depends on the spectrum of action of the drug, duration of therapy, patient age, metabolic status, and initial microbiota composition.
The following is a summary of information based on FDA publications and clinical reviews.
Table: antibiotics and the nature of their impact on the microbiome
| Group of antibiotics | Impact on the microbiome | Main risks described in studies |
|---|---|---|
| Penicillins | Significant reduction in the diversity of anaerobic bacteria | antibiotic-associated diarrhea, candidiasis |
| Macrolides | Long-term changes in bacterial populations (up to 6–12 months) | impaired barrier function, risk of resistant strains |
| Cephalosporins | High impact on Bifidobacterium and Lactobacillus | indigestion, bloating, diarrhea |
| Fluoroquinolones | Imbalance between Firmicutes/Bacteroidetes | metabolic changes, risk of overgrowth of Enterobacteriaceae |
| Tetracyclines | Broad effect on obligate anaerobes | decreased SCFA production, photosensitization |
| Aminoglycosides | Limited exposure (low absorption) | local changes in intestinal flora |
| Sulfonamides | Reduction in populations of bacteria involved in vitamin synthesis | deficiency states, metabolic changes |
Research published in Nature confirms that even short courses of antibiotics can reduce bacterial diversity by 20–30%, and full restoration of the microbiome can take from a few weeks to a year.
Clinical consequences of antibiotic-induced dysbiosis
Based on the reviews of the WHO and Mayo Clinic, several main groups of consequences can be distinguished:
• digestive disorders (bloating, diarrhea, change in food tolerance)
• modification of the immune response, including increased incidence of viral infections
• risk of C. difficile-associated diarrhea
• endocrine changes due to impaired fatty acid metabolism
• increased risk of allergic reactions
• impact on psycho-emotional state due to disruption of the gut-brain axis«
In children, these effects are more pronounced, especially under the age of three, when the microbiome is in the formation phase.
Analyses and methods for assessing the microbiome after antibiotics
To assess the state of microbial balance, the following are used:
• DNA metagenomic sequencing (16S rRNA)
• comprehensive bacteriological profiles
• stool analysis with SCFA study
• tests for yeast-like fungi
• assessment of inflammatory markers (calprotectin, lactoferrin)
Clinical protocols recommend evaluating the microbiome in cases of recurrent diarrhea, frequent infections, decreased immunity, or after using several antibiotics in a row.
Strategies for supporting and restoring the microbiome
Based on current research, the following microbiota play a key role in restoring:
• high fiber content in the diet (prebiotic effect)
• fermented foods
• adequate water consumption
• moderate physical activity
• limiting added sugar
• use of probiotic strains (as recommended by a doctor)
Scientific reviews emphasize that probiotics are not a universal solution, but in some cases they reduce the risk of antibiotic-associated diarrhea and accelerate the recovery of certain bacterial populations.
The microbiome is a renewable system, but the speed and completeness of its recovery depend on the initial state of the organism, age and diet. Formal scientific analysis confirms that responsible use of antibiotics, rational nutrition and, if necessary, laboratory monitoring help to minimize the negative consequences of antibiotic therapy and maintain a normal microbial balance.
