Lactobacillus species are probiotics commonly investigated as alternatives or adjuncts to antibiotics, particularly for preventing or treating infections such as antibiotic-associated diarrhea, Clostridioides difficile infection, and some urogenital and respiratory tract infections. Scientific evidence shows that certain strains of Lactobacillus can help restore and maintain healthy microbiota disrupted by antibiotic treatment. Several randomized controlled trials and systematic reviews have found that Lactobacillus probiotics can reduce the incidence and duration of antibiotic-associated diarrhea and may help prevent C. difficile infection, especially in children and adults at risk.

The mechanisms proposed include competitive exclusion of pathogens, production of antimicrobial substances (like lactic acid and bacteriocins), and modulation of host immune responses. However, the evidence supporting Lactobacillus as a direct substitute for antibiotics in treating acute bacterial infections is limited; most studies support their use as adjuncts rather than stand-alone alternatives. Additionally, efficacy is strain-specific and not all commercially available probiotics have demonstrated clear benefits. Overall, the use of Lactobacillus is scientifically validated for some supportive roles in infection management, but not as a direct replacement for antibiotics in established bacterial infections.