SYNERGISTIC EFFECTS OF MICROBIAL-SYNTHESIZED NANOPARTICLES ON MULTIDRUG-RESISTANT BACTERIAL BIOFILMS

Zainab Nawaf Hammad Al-Jughayfi

Авторы

Zainab Nawaf Hammad Al-Jughayfi College of Education for Women, University of Mosul, Nineveh, Iraq

Ключевые слова:

Microbial Nanoparticle Synthesis, Synergistic Antibacterial Efficacy, Bacterial Biofilms, Multidrug Resistance, Silver Nanoparticles

Аннотация

Multidrug-resistant (MDR) pathogens are major contributors to bacterial biofilms, which are an increasing global health threat and are highly tolerant of planktonic cell concentrations of antibiotics, sometimes as much as 1000-fold greater. In this study, we evaluated the antibiofilm efficacy of the synergistic effect of the synthesized extracellularly biogenic silver nanoparticles (bio-AgNPs) produced by Bacillus subtilis ATCC 6633 in combination with clinical antibiotics, colistin and vancomycin against the refractory clinical isolates of Pseudomonas aeruginosa (MDR-PA01) and methicillin-resistant Staphylococcus aureus (MRSA-ST570). The physicochemical characterization confirmed that the nanocrystals are spherical, face centered cubic (fcc), and have an average core diameter (TEM) of 18.4 ± 2.6 nm, apparent hydrodynamic diameter (DLS) of 32.8 ± 2.1 nm, a stable zeta potential of −29.6 ± 1.4 mV, and a distinct surface plasmon resonance peak at 421.0 ± 0.5 nm. Checkerboard microdilution assays showed very high synergy for both MDR pathogens giving identical fractional inhibitory concentration indices (FICI) of 0.250 and an 8-fold reduction in minimum inhibitory concentrations (MICs). In mature 48-hour biofilms, the synergistic combination of nano-antibiotics reduced the biomass of P. aeruginosa by 88.4 ± 1.7% and MRSA by 86.1 ± 1.9% and resulted in an ESCC of > 5.2 log₁₀ CFU/mL. In parallel, this architectural collapse led to a biochemical loss of extracellular polymeric substances (EPS): 76.8% decrease in matrix carbohydrates and 82.5% decrease in extracellular DNA (eDNA). The excellent biocompatibility was confirmed by hemolysis assays (<1.9%) and mammalian fibroblast viability assays (>93%) at synergistic therapeutic concentrations, indicating the potential of these biogenic nanocomposites as promising translational platforms for biofilm eradication.

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