Abstract

The efficacy of 30 ppb silver in 0.3 Hydrogen peroxide solution for disinfection of selected enterobacteria including Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae was assessed in suspension and on surface. Mentioned bacteria exposed to the treatment solution for 72 hours in nutrient suspension and for 15 minutes on a steel surface. The bactericidal capability was determined by means of conventional colony counting and optical density (OD) at 450 nm. There were significant differences in OD of K. pneumoniae and P. mirabilis suspension between treatment and control groups during three 24 hours intervals (CI=0.95, P=0.000, for both), along with no growth on solid media at 24 and 48 hours of exposure. Results for E. coli were different; during initial exposure times, OD of E. coli decreased slightly in treatment group but unexpectedly increased after 24 hours. Colonies grown on plate confirmed this OD increment was because of viable E. coli in the suspension. It is possible that decomposition of H2O2 and reduction of its concentration after 24 hours allowed undamaged E. coli to grow. For surface decontamination test, there were significant differences between pre and post disinfection steps (For all bacteria CI=0.95, P<0.05). In conclusion, results of the current study proposed strong disinfection effect of the treatment solution against three important human pathogens; E. coli, P. mirabilis and K. pneumoniae, both in suspension and on surface. © IDOSI Publications, 2013.