Exploring the Potential Effects of Nisin and Colistin CombinationsAgainst Drug-Resistant Klebsiella pneumoniae Isolates

Background:Klebsiellapneumoniaeis a formidable nosocomial pathogen increasingly known for its antibiotic resistance,posing a significant global health challenge. The emergence of carbapenem-resistant strains has necessitated the exploration ofalternative therapeutic strategies. Objectives: This study aimed to evaluate the synergistic effects of combining nisin with colistin against K.pneumoniae isolatesand to determine whether this combination enhances antibacterial efficacy compared to colistin alone. Methods: Ten K.pneumoniae isolates were collected from hospitalized patients in Iran. Antimicrobial susceptibility testing wasconducted using the Kirby-Bauer disk diffusion method. Minimum inhibitory concentration (MIC) assays were performed todetermine the MICs of Nisin and Colistin. Synergistic activity testing, biofilm formation assays, and time-kill assays were alsocarried out to assess the effectiveness of the nisin-colistin combination. Results: The study demonstrated that the nisin-colistin combination exhibited a synergistic effect, significantly reducingcolony counts over 24 hours for select isolates. However, the combination did not show statistically significant superiority inantibiofilm activity compared to colistin alone. The time-kill assay confirmed the synergistic effect, showing a notable reductionin colony counts within 24 hours. These findings underscored the complexities of biofilm structures and their resistancemechanisms, highlighting the necessity for further research to optimize treatment outcomes. Conclusions: This study provides a novel perspective on addressing antibiotic resistance in K.pneumoniae by evaluating thesynergistic potential of the nisin-colistin combination. The findings contribute to the development of innovative therapeuticapproaches to manage infections caused by this challenging pathogen