Objectives: To develop a more accurate and rapid way to quantify bacteria in CRT kits.
Methods: 85 saliva samples were taken from human volunteers and applied on the CRT kits. Two digital pictures of S. mutans colonies were taken from each CRT kit and the files were analyzed using Media-Cybernetics Image-Pro-Plus 4.5 graphical processing software. The software counted the light spots reflected from the bacterial colonies using predetermined physical characteristics. The digitized analysis counts were converted to ln units. A statistical comparison was made between the semi quantitative colony count (as recommended by manufacturer of the CRT kit) and the digital/computerized analysis developed in our laboratory.
Results: Statistical analysis of the results indicated that a good correlation between the digitized analysis and the semi quantitative method r=0.86 ; p<0.01. Separating the digitized counts into four ranges was statistically similar to the 4 ranges of the semi quantitative classes p<0.01. Reproducibility of two independent digitized counts was of a correlation value of r^2=0.998.
Conclusions: The digital/computerized quantification of the kits provides a useful tool for quantitative evaluation of bacterial count. The major bias observed was due to light reflection from other light sources. This method may apply for rapid and accurate bacteria count on any agar surface and for automation of the bacterial counting process.