VOLUME 63 : 2015

Inadequacy of effective drugs to control infections is a result of antimicrobial resistance. With the constraint in antibiotic usage, there is a delusion that there may not be a cure to infections that were once treatable. Employing metal oxide nanoparticles, zinc oxide in particular, to which pathogens are unlikely to exhibit resistance could be a promising approach.Microwaveassisted technique involving the reaction of zinc acetate dihydrate and ammonium hydroxide was used in the synthesis of zinc oxide nanoparticles (ZnO NPs). Sensitivity of ZnO nanoparticles and bulk against isolated uropathogens was determined through agar-well diffusion and time kill assay. Determinations of minimum inhibitory and minimum bactericidal concentrations were based on absorbance reading at 600 nm. The ZnO NPs viewed with the transmission electron microscope were rod-shaped averaging 23.90±2.66 x 10.73±1.74 nm. Superiority of ZnO NPs over ZnO in bulk can be observed at all test concentrations against the six urinary tract infections (UTI) bacterial pathogens (p<0.05). Of the isolated pathogens, Pseudomonas mendocina was the most susceptible with 28.67±0.58 mm zone of inhibition at 10 mg/mL ZnO NP. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) varied with the uropathogens. MICs of ZnO NPs were between 0.6–0.9 mg/mL while MBCs were between 0.7–4 mg/mL. Time-kill endpoints of the pathogens at MBC of the nanoparticles were 1 h for P. mendocina and Proteus mirabilis, 3 h for Citrobacter freundii and Escherichia coli, and 6 h for Klebsiella pneumoniae ssp. rhinoscleromatis. Growth (CFU/mL) of Serratia marcescens was down to 90% at 6 h, hence, would have reached 99% at 24 h.

Keywords: urinary tract infection, zinc oxide nanoparticles, zone of inhibition, minimum inhibitory concentration, minimum bactericidal concentration, time-kill endpoint