Validation of Blue Light Imaging Technology for the Detection of Viable Microcolonies

Abstract

The possibilities and simplicity of visual colony counting have made it the mainstay of microbiological analysis for more than a hundred years. A main disadvantage of the method is the long time required to generate visible colonies from microbes in a sample. New technologies and automation have emerged in recent years to challenge this mainstay of microbiological analysis. Among these new technologies, the Growth Direct® System uses digital imaging of cellular autofluorescence to detect and enumerate growing microcolonies many generations before they become visible to the human eye by using blue light to excite microbes to autofluorescence. There may be concerns, however, that viable microcolonies are damaged or killed by the energy they are exposed to during excitation. To show that the amount of energy generated by the Growth Direct® System does not have any negative effect on viable microcolonies, four different test series have been prepared and compared to each other. The novel technology was described, and the testing performed which determined that the enumeration by the Growth Direct® System was accurate and did not affect the viable microcolonies using blue light illumination. Key words: Growth Direct®, colony counter, automation, blue light, validation