Most aerobic bacteria grow on the paler TTC culture medium. The TTC dye stains most colonies red for easy analysis. Bacterial colonies usually appear as red spots but can also appear colourless. Compare the density of both red and colourless colonies with the comparison chart overleaf to estimate the number of organisms in the fluid being tested.
If the bacterial content of the fluid is high, a confluent growth can appear on the surface of the slide rather than distinct colonies. If this confluent growth is colourless, it could be misinterpreted as ‘no growth’. For accurate results, it is recommended that the slide is examined using a reflected light against a sterile unused dip slide for comparison.