Probiotic Cell-free Supernatants vs. Viable Cells: Antimicrobial Activity Against Klebsiella Pneumoniae in Wound Care

The rise of Gram negative pathogens poses a serious threat to public health due to their high resistance to existing antibiotics and lack of novel therapeutic options. Klebsiella pneumonia is one of the pathogens frequently isolated from chronic wounds, where it contributes to delayed healing, increased inflammation, and consequently, enhanced risk of complications. Its ability to withstand conventional treatments highlights the urgent need for alternative antimicrobial strategies, especially as multidrug resistant (MDR) strains become increasingly prevalent. This challenge is further amplified in the context of diabetic foot ulcers (DFUs), a serious complication of the metabolic disease diabetes mellitus. In these wounds, sustained hyperglycemia creates an ideal environment for bacterial colonization and immune dysfunction, making infection control particularly difficult. The dual burden of impaired healing and MDR infections calls for innovative approaches that target both microbial and metabolic dysregulation. Probiotics are emerging as promising candidates due to their antimicrobial and immunomodulatory properties. In this study, four probiotic strains, Lactobacillus rhamnosus, Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus gasseri, were evaluated for their ability to inhibit a resistant strain of K. pneumoniae. Cultures were grown under anaerobic conditions, and both cell free supernatants and viable cells were prepared and tested in simulated wound fluid under microaerophilic conditions. To replicate diabetic wound environments, experiments were conducted under both hyperglycemic and normoglycemic conditions (20 mM and 5 mM, respectively) over 24 hours. Among the supernatants, L. plantarum demonstrated the most potent antimicrobial effect in both environments while L. gasseri was the least effective showing that glucose levels had little impact on the efficacy of cell free supernatants. On the other hand, the antimicrobial activity of live probiotic cells was clearly influenced by glucose concentration. Under hyperglycemic conditions, L. rhamnosus and L. plantarum reduced K. pneumoniae growth by approximately fourfold and fivefold, respectively, whereas their efficacy was diminished under normoglycemic conditions. These findings suggest that select probiotic strains, particularly L. rhamnosus and L. plantarum, may serve as effective antimicrobial agents against K. pneumoniae, especially in the hyperglycemic environment characteristic of diabetic wounds. This highlights their potential role in the development of targeted, adjunctive therapies for managing DFUs complicated by resistant Gram negative infections.