Laser speckle time-series correlation analysis for bacteria activity detection

The study aims at development and laboratory approbation of non-contact optical technique for early evaluation of microbial activity. Microorganisms' activity is estimated by laser speckle contrast imaging technique in combination with image processing of obtained time varying speckle patterns. Laser speckle patterns were captured by CMOS sensor during illumination of growing bacteria colonies by low power (<30 mW, 635 nm) stabilized coherent light source. To validate proposed technique and image processing algorithm the vibrio nafriegens bacteria are used. After analysis of several different experiments the following results were obtained: In the central part of the colony activity can be seen in 2.5-3 hours. Thus, earlier detection of bacterial activity is expected, i.e., earlier than 2-3 hours, which is much earlier than the standard counting methods used to count colony forming units (CFU).