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

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 <3.125 ppm, 25 ppm, <3.125 ppm, and <3.125 ppm, respectively, while those for S. pneumoniae and MRSA 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.

Selected Mutations by Nemonoxacin and Fluoroquinolone Exposure Among Relevant Gram-Positive Bacterial Strains in Taiwan.

Nemonoxacin is a nonfluorinated quinolone with good bactericidal effects against quinolone-resistant Gram-positive microorganisms. The in vitro inducible resistance of nemonoxacin against clinically relevant Gram-positive pathogens was compared with ciprofloxacin, levofloxacin, and moxifloxacin. Three strains of each bacterial species, including Streptococcus pneumoniae, Staphylococcus aureus, Enterococcus faecium, and Enterococcus faecalis, were cultured. All clinical isolates had wild-type gyrA, gyrB and parC, parE before further in vitro test. DNA sequencing for the quinolone resistance determination region (QRDR) of gyrase and topoisomerase genes was performed. Nemonoxacin had the lowest minimum inhibitory concentrations (MICs) among all quinolones. During exposure to nemonoxacin, the MIC values did not increase for S. aureus, E. faecium, and E. faecalis, and revealed fourfold increase of S. pneumoniae over three cycles of a stepwise resistance selection. DNA sequencing did not show inducible QRDR resistance of nemonoxacin group. Compared to other fluoroquinolones, nemonoxacin has a low potential for inducing resistant pathogens.

Molecular epidemiology and control of nosocomial methicillin-resistant Staphylococcus aureus infection in a teaching hospital.

BACKGROUND AND PURPOSE: Nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection is difficult to control. Due to a dramatic increase in the nosocomial MRSA infection rate at our hospital from 2000 to 2001, this study was conducted to identify the source of these infections and the effectiveness of control measures. METHODS: 179 healthcare workers (HCWs) were screened for carriage of MRSA. Starting in April 2001, all patients with MRSA infection or colonization were put in strict contact and cohort isolation. The bacterial isolates of HCW carriers and patients with MRSA infection from April 2001 to September 2001 were subjected to antimicrobial susceptibility testing by disk-diffusion method and molecular typing by pulsed-field gel electrophoresis (PFGE). RESULTS: Fifteen HCWs were found to be carriers of MRSA. They were all given topical mupirocin treatment. After these interventions, the nosocomial MRSA infection rate decreased from 1.23 to 0.53 per 1000 patient-days. All 61 MRSA isolates available for antimicrobial susceptibility testing and molecular typing were multidrug resistant. PFGE study revealed 2 predominant types, type C and type Y, comprising 36 and 12 isolates, respectively. CONCLUSIONS: The current study demonstrates the importance of measures to control nosocomial MRSA infections in hospitals that already have a high incidence of endemic MRSA infection. Elimination of carriage by healthcare workers, and strict contact and cohort isolation are the main effective measures.