Abstract
The treatment of bacterial infections has been successfully achieved when antibiotics
were first introduced. A short while after the introduction of antibiotics, bacterial strains
became resistant to antibiotic treatment, and bacterial infections were potentially fatal
once again. This challenge has led to various pursuits of antibiotic alternative treatment.
The antibacterial effect of colloidal silver (18 and 20 ppm) was investigated on
Staphylococcus aureus and Streptococcus pyogenes in vitro using the microdilution
method. Agar disc diffusion method was used as trial run. Zones of inhibition were
measured and recorded in the agar disc diffusion method to indicate bacterial inhibition.
The Iodonitrotetrazolium chloride dye was added to the 96 well microplate in the
microdilution method and colour changes were visually observed. An unchanged clear
colour indicated bacterial inhibition. Noticeable colour changes (from a clear colour to
purple) indicated bacterial growth. The results from both experimental methods showed
that both 18 and 20 ppm colloidal silver had an inhibitory effect against Streptococcus
pyogenes, but not against Staphylococcus aureus. This warrants further extensive
research on the effect of colloidal silver as an antimicrobial.