Nanoemulsion-Mediated Suppression of Multidrug-Resistant Klebsiella pneumoniae via Oxygen Consumption Reduction and Biofilm Inhibition.

In this study, seven water‑in‑oil (W/O) nanoemulsion (NE) (NE-21 to NE-27) were developed via high-pressure microfluidization (100-500 nm droplets, Zeta-potential - 3.6 to + 64.5 mV) The formulations comprised sunflower, castor, or olive oils, non‑ionic surfactants Tween‑60 and Brij‑30 (6-8%), cetylpyridinium chloride (1%), and active agents including silver nanoparticles (0.05%) and sodium hypochlorite (2.5%). From over thirty preliminary formulations, seven were selected based on physicochemical stability, with no phase separation observed over seven days at 25 °C. Then evaluated against Klebsiella pneumoniae reference strains (ATCC 35657, MTCC 432) and clinical multidrug‑resistant (MDR) Klebsiella spp. clinical isolates (CI-1 to CI-3). NE-25/NE-26 showed notable antimicrobial activity (MIC 40-94 µg/mL, 45-106 × dilutions), rapid bactericidal action (30 min), 83.92% biofilm inhibition, and metabolic suppression (OCR 0.11 nmol mL⁻1 min⁻1) despite minimal membrane damage (< 10% leakage). Low hemolytic activity under static agar conditions and high NIH/3T3 cell viability (NE-23/25 > 240% at 100 μL via MTT) acceptable biocompatibility. Favorable pH (4.46-6.27), spreadability (53-139 mm2), and controlled release (10-22% in 24 h) support topical use against Klebsiella, combining multi-target efficacy with acceptable safety.