Introduction: The presence of most indicator organisms such as total aerobic count (TC), yeast and mold (YM), coliform and E. coli (EC) can be determined by the time consuming plate count methodology. In recent years the application of rapid automated methods, as alternatives to the plate count method, has become increasingly significant. BioLumix has developed a new optical system for rapid and automated detection of indicator microorganisms.
Purpose: To evaluate the new system and technology for the detection of TC, YM, coliform and EC, and show its applicability to environmental and UHT products testing.
Methods: The BioLumix system detects optical changes, due to microbial growth in liquid growth medium containing optically sensitive reagents (color or fluorescence). An embedded optical sensor for the detection of CO2, was used for TC and YM. The simultaneous detection of coliform and E. coli was achieved with a combination of color and fluorescent dyes. Stainless steel coupons inoculated with various types of bacteria, yeast and mold were swabbed. The inoculated swabs were tested for TC, YM or a combination of coliform/EC. UHT products were evaluated for the presence/absence of microorganisms using the BioLumix system.
Results: The surface of stainless steel coupons was inoculated with 83 different strains of bacteria, 14 molds and 12 yeasts. All detected by the CO2 sensor, while none of the un-inoculated samples were detected. The coliform/EC vial was capable of distinguishing between coliform and E. coli in environmental samples. There were 37 store-bought UHT products tested including: milk, half & half, shakes, and whipped cream. Additionally, 71 products were inoculated with low numbers of bacteria or yeast. The system clearly distinguished between clean and contaminated samples. Significance: The data suggests that the new method is useful for determining total aerobic count, yeast and mold as well as coliform and E. coli. More assays are currently under development.