Antibacterial effects of Hydrogen peroxide and silver composition on selected pathogenic enterobacteria

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.