Rapid Methods and Automation in Food Microbiology
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‘pressurized’ into all 48 chambers to distribute exactly one ml of the sample into the 16-tube MPN system. After, the filled cards with the delivery tube cut and sealed automatically are placed into an incubator (e.g. 35 C) and incubated overnight. After incubation a series of cards are placed in an instrument to read the presence of fluorescence in each of the 48 chambers per card due to biochemical reactions of the target organisms (total count, coliform count, etc.) in the liquid. The instrument automatically calculates the 16-tube 3-dilution series MPN of the sample. The entire procedure is highly automated with no need for a technician to transfer samples into a large number of tubes, and after incubation to read the color change or turbidity in each tube, as in the conventional 3-tube or 5-tube MPN methods to determine the viable cell count. The savings of time of operation and materials by TEMPO compared to the conventional MPN method are truly impressive. This author predicts that the system will be well received by food and water microbiologists.
II.C. Aerobic, anaerobic, and ‘real time’ viable cell counts By using the correct gaseous environment or suitable reducing compounds one can obtain aerobic, anaerobic, facultative anaerobic microbial counts in products. Typically, microbial counts were obtained in 24–48 hours. Several methods have been developed and tested in recent years that provide ‘real’time viable cell counts, such as (1) the use of ‘vital’stains (Acridine Orange) to report living cells under the microscope to count fluorescing viable cells (Direct Epifluorescent Filter Technique), (2) scanning cells interacted with Fluorassure (a vital dye in Chemunex Scan RDI system), and (3) measuring ATP of microcolonies trapped in special membranes (MicroStar System of Millipore), among other methods. These real-time tests can give viable cell counts in about 4 hours. A simple Fung Double Tube system using appropriate agar and incubation conditions was developed more than 20 years ago by the author for food. This system was evaluated for water testing in 2007 (Fung et al., 2007) and can provide a Clostridium perfringens count in about 6 hours. Hawaii is the only U.S. state to use C. perfringens as an indicator of fecal contamination. This information can be used to assess suitability for recreation and swimming in various beaches around the world.
III. ADVANCES IN MINIATURIZATION AND DIAGNOSTIC KITS Identification of normal flora, spoilage organisms, clinical and foodborne pathogens, starter cultures, etc., in many specimens, is an important part of microbiology. This author systematically miniaturized biochemical reactions to identify and characterize large numbers of microbes in food and water in the Microtiter system in the late 1960s and early 1970s, which