Metal nanoparticles and nanoparticle composites are effective against Haemophilus influenzae, Streptococcus pneumoniae, and multidrug-resistant bacteria

Abstract

Background: Treatment for lower respiratory tract infection caused by multidrug-resistant organisms (MDRO) are often limited. This study explored the activity of different metal nanoparticles against several respiratory pathogens including MDROs. Methods: Clinical isolates of carbapenem-resistant Acinetobacter baumannii (CRAB), carbapenem-resistant Klebsiella pneumoniae (CRKP), Pseudomonas aeruginosa, Haemophilus influenzae, methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus pneumoniae were tested for in vitro susceptibilities to various antibiotics and nanoparticles. Minimum inhibitory concentrations (MICs) of silver-nanoparticle (Ag-NP), selenium-nanoparticle (Se-NP), and three composites solutions ND50, NK99, and TPNT1 (contained 5 ppm Ag-NP, 60 ppm ZnO-nanoparticle, and different concentrations of gold-nanoparticle or ClO2) were determined by broth microdilution method. Results: Fifty isolates of each bacterial species listed above were tested. Ag-NP showed lower MICs to all species than Se-NP. The MIC50s of Ag-NP for CRAB, CRKP, P. aeruginosa, and H. influenzae were 50 ppm and 50 ppm. Among CRAB, CRKP and P. aeruginosa, the MIC50s of ND50, NK99, and TPNT1 for CRAB were the lowest (1/8 dilution, 1/8 dilution, and 1/8 dilution, respectively), and those for CRKP (>1/2 dilution, 1/2 dilution, and 1/2 dilution, respectively) were the highest. Both MRSA and S. pneumoniae showed high MIC50s to ND50, NK99, and TPNT1. Conclusions: Metal nanoparticles had good in vitro activity against Gram-negative bacteria. They might be suitable to be prepared as environmental disinfectants or inhaled agents to inhibit the growth of MDR Gram-negative colonizers in the lower respiratory tracts of patients with chronic lung diseases.

Keywords

• Respiratory infections
• Metal nanoparticles
• Multidrug-resistant organisms
• Antibacterial therapy