Antibiotic overuse has contributed to the emergence of multidrug-resistant (MDR) bacteria, posing a serious public health threat. Pets may act as reservoirs of MDR bacteria, with the potential to transmit these pathogens to humans. This study aimed to identify probiotic alternatives to antibiotics by isolating and evaluating lactic acid bacteria (LAB) from feline milk. In addition to conventional in vitro assessments such as growth kinetics, adhesion ability, safety, and antipathogenic activity, this study also evaluated the antioxidant capacity and production of beneficial metabolites. Three LAB strains were isolated from feline milk, including two strains of Lactobacillus plantarum (M2 and M3) and one strain of Weissella confusa (M1). Resistance assays revealed that strains M2 and M3 exhibited high survival rates under stress conditions, including exposure to bile salts, acidic environments, artificial intestinal and gastric juice. Notably, strain M3 demonstrated strong auto-aggregation ability (73.39%) and high hydrophobicity toward trichloromethane (62.16%). It was also nonhemolytic and susceptible to various β-lactam antibiotics. Furthermore, strain M3 exhibited potent antimicrobial activity in both co-aggregation and Oxford cup assays. Overall, L. plantarum M3 displayed superior probiotic properties, suggesting its potential as an adjunct or alternative to antibiotics in managing MDR bacterial infections in cats.

The global restriction or elimination of antibiotic growth promoters (AGPs) has intensified the search for effective and sustainable alternatives in livestock production. Among the proposed strategies, probiotic supplementation has received increasing attention due to its potential to enhance animal health and productivity while reducing reliance on antibiotics. Lactobacillus acidophilus (L. acidophilus), a well-characterized lactic acid bacterium commonly found in the gastrointestinal tract of animals, has been widely investigated as a probiotic candidate in livestock systems. This review summarizes current knowledge regarding the biological characteristics and mechanisms of action of L. acidophilus, including pathogen inhibition, modulation of intestinal barrier function, and regulation of host immune responses. Practical considerations, including the effects of feed processing on bacterial viability, strain stabilization technologies, and dose–response relationships, are also discussed. Reported supplementation doses in livestock trials typically range from 10⁶ to 10⁹ CFU/kg feed or per animal per day, although dose–response relationships remain poorly defined. Furthermore, recent advances in the application of L. acidophilus in major livestock species—including swine, poultry, and ruminants—are critically evaluated, with emphasis on growth performance, gut microbiota modulation, and disease resistance. Emerging approaches such as postbiotic utilization and probiotic-based vaccine adjuvants are also discussed. In addition, the potential contribution of L. acidophilus to environmental sustainability and mitigation of antimicrobial resistance dissemination in livestock systems is examined. Overall, L. acidophilus represents a promising component of integrated strategies aimed at improving animal health and promoting sustainable livestock production, although further research is required to clarify strain-specific effects and optimize practical applications.