Probiotics in Infectious Diseases: The Perfect Complement to Antimicrobial Therapies?
Speaker: Dr. Lena Biehl, Germany
Key Highlights:
A comprehensive overview on the use of probiotics in infectious disease management was presented. The potential of probiotics as adjuncts to antimicrobial therapy was examined, covering definitions, regulatory aspects, clinical evidence, and disease-specific uses.
Historical Origins of Probiotics:
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The concept of probiotics was observed long ago, with early notions of bacterial antagonism being recognized.
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Credit for popularizing the idea of probiotics has been given to Ilya Mechnikov, a Russian scientist working at the Pasteur Institute in Paris. It was hypothesized by Mechnikov that harmful microbes in the gut could be replaced with beneficial ones.
Definition and Classification of Probiotics:
Probiotics have been defined by the WHO as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.” Related concepts such as prebiotics, synbiotics, and postbiotics were also discussed.
Probiotics vs. Drugs:
Although probiotics can function like drugs, they are not classified as drugs by default. Probiotics are usually offered as:
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Dietary or nutritional supplements (e.g., yogurts or capsules),
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Aimed at promoting general health and wellness.
In contrast, drugs are used to treat specific diseases or conditions with defined endpoints.
Regulatory Differences:
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Dietary supplements are not required to obtain pre-approval from authorities.
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It must be demonstrated that the product is safe, but health claims are not mandated to be proven.
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Drugs, however, must prove efficacy in treating a specific condition and undergo a more stringent regulatory process.
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Microbiome-based therapies, including engineered live bio-therapeutics and microbial consortia, fall on the drug side of the spectrum.
Evidence for Use with Antibiotics:
The focus was shifted to the evidence behind probiotic use, particularly in complementing antibiotic therapy.
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Antibiotic-Associated Diarrhea (AAD)
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A Cochrane meta-analysis of ~6,000 patients indicated that the risk of AAD was reduced by 37% when probiotics were co-administered with antibiotics. A number needed to treat (NNT) of 20 was observed.
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The most effective strains included Lactobacillus acidophilus, Saccharomyces boulardii, and Bifidobacterium spp.
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Clostridioides difficile Infection (CDI)
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Probiotics were shown to reduce CDI risk in high-risk populations (baseline risk ≥4%), as per a 2017 Cochrane review. No benefit was demonstrated in low-risk groups.
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Therefore, use in CDI prevention was recommended only for selected high-risk patients receiving broad-spectrum or prolonged antibiotic therapy.
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Timing of Probiotic Administration
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Concurrent use during antibiotic treatment was found to be beneficial.
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Post-antibiotic administration was shown—via a human-mouse crossover study—to delay natural microbiota recovery, particularly in comparison to fecal transplant or spontaneous recovery.
Applications in Specific Infections:
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Helicobacter pylori: A modest improvement in eradication rates (OR 1.14) and a reduction in gastrointestinal side effects were observed when probiotics were added to standard therapy, based on 34 Randomized Controlled Trials (RCTs).
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Recurrent Urinary Tract Infections (rUTIs)
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Oral probiotics did not reduce recurrence, as per a 2015 Cochrane review.
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Vaginal formulations, particularly with Lactobacillus crispatus, showed potential, though phase 3 trials are still lacking.
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Current European and German guidelines do not endorse their use but allow shared decision-making.
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Vaginal Infections: Although widely used in clinical practice for bacterial vaginosis and candidiasis, the evidence remains heterogeneous. No firm consensus exists on strain-specific efficacy.
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Preterm Infants: Probiotics were associated with reduced risks of necrotizing enterocolitis (NEC), sepsis, and mortality in preterm infants. While European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) recommends certain strains, formal guideline endorsement has yet to be achieved.
Limitations and Safety:
Significant heterogeneity among strains and formulations was noted, complicating generalizability and clinical research. Lack of product standardization continues to pose challenges. Safety concerns were raised for immunocompromised individuals and those with compromised gut barriers, though most side effects were mild and gastrointestinal.
Conclusion:
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Probiotics were shown to reduce AAD and hold potential as adjuncts in H. pylori infection and vaginal dysbiosis.
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Use should be individualized, considering patient risk profiles and the strain-specific nature of current evidence.
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More robust, indication-specific, and strain-specific trials are needed to guide standardized clinical application.
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While the role of probiotics in infectious disease appears promising, their integration into routine clinical practice should be cautious and evidence-driven.
ESCMID Global, April 11-15, 2025, Vienna
