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- Bactericidal efficacy of molybdenum oxide nanoparticles against antimicrobial-resistant pathogensPublication . Lopes, Elizeth; Piçarra, S.; Almeida, Pedro L.; Lencastre, H. de; Aires-de-Sousa, MartaMultidrug-resistant bacteria pose a major threat to effective antibiotics and alternatives to fight multidrug-resistant pathogens are needed. We synthetized molybdenum oxide (MoO3) nanoparticles (NP) and determined their antibacterial activity against 39 isolates: (i) eight Staphylococcus aureus, including representatives of methicillin-resistant S. aureus epidemic clones; (ii) six enterococci, including vancomycin-resistant isolates; and (iii) 25 Gram-negative isolates (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae), including extended spectrum beta-lactamases and carbapenemases producers. All isolates showed a MoO3 NP MIC of 700–800 mg l−1. MoO3 NP produced a clear inhibition zone for S. aureus and all Gram-negative isolates at concentrations ≥25 mg ml−1 and ≥50 mg ml−1 for enterococci. When the NP solutions were adjusted to pH ~7, the biocidal activity was completely abolished. MoO3 NP create an acidic pH and show a universal antimicrobial activity against susceptible and resistant isolates belonging to the most relevant bacterial species responsible for hospital-acquired infections.
- Novel coating containing molybdenum oxide nanoparticles to reduce Staphylococcus aureus contamination on inanimate surfacesPublication . Piçarra, Susana; Lopes, Elizeth; Almeida, Pedro L.; Lencastre, Hermínia de; Aires-de-Sousa, MartaWe previously synthetized molybdenum oxide (MoO3) nanoparticles (NP) and showed their antibacterial activity against a representative collection of the most relevant bacterial species responsible for hospital-acquired infections, including Staphylococcus aureus. The aim of the present study was to prepare and characterize a novel coating with these MoO3 NP, confirm its mechanical stability, and investigate its biocidal effect to reduce S. aureus contamination on inanimate surfaces. In addition, the novel MoO3 NP coating was compared to a silver (Ag) NP coating synthetized by the same procedure. The MoO3 and Ag NP coatings were characterized in terms of their chemical structure by FT-IR, surface morphology by scanning electron microscopy, and mechanical properties by tensile and adhesion tests. The antimicrobial activity of the coatings was tested by following the loss of viability of S. aureus after 6h, 24h, 48h, and 72h exposure. MoO3 and Ag coatings exhibited surfaces of comparable morphologies and both presented elastomeric properties (tensile strength of similar to 420 kPa, Youngs modulus of similar to 48 kPa, and maximum elongation of similar to 12%), and excellent (classification of 5B) adhesion to glass, steel and polystyrene surfaces. The two coatings exhibited a good antibacterial activity (R) against S. aureus over time (R-MoO3 = 0.20.81; R-Ag = 0.612.37), although the effect of the Ag NP coating was more pronounced, especially at 72h (R-MoO3 = 0.81 vs R-Ag = 2.37). Noteworthy, contrary to the Ag NP coating, the MoO3 NP coating was colourless and transparent, avoiding undesired unaesthetic effects. The synthetized coating with NP of MoO3, which has low toxicity to humans, capability of biodegradation, and rapid excretion, can be applied onto most standard materials and therefore is a promising tool to reduce S. aureus contamination on usual inanimate surfaces found in healthcare and community environments.