MPN (TEMPO)

An automated MPN method, TEMPO®, has been designed by BioMérieux  which can be used for the enumeration of a variety of target organisms including Enterobacteriaceae, Escherichia coli, Total Viable Count and Coagulase‐positive Staphylococci. The TEMPO® system is based on a 16 × 3 MPN technique in which a disposable MPN ‘card’ is automatically filled with a pre‐prepared dilution of the food sample, together with the TEMPO® reagent. The plastic card consists of three rows of 16 wells each, with a well volume of 225 μl in the first row, 22·5 μl in the second row and 2·25 μl in the third. This difference in volumes effectively achieves a tenfold dilution between one row and the next. The card is incubated and then placed in an automated reader, which detects fluorescence. Glucose fermentation by Enterobacteriaceae causes acidification of the reagent which results in the quenching of fluorescence in positive reaction tubes. A confirmed Enterobacteriaceae result can be obtained by the TEMPO® method in 24 h.

Spiral  

The Spiral® method enables the automatic and standardized plating of a sample - allowing 4 dilution series on one Petri dish. The sample is plated in a form of an increasingly dilute spiral (from the center to the periphery). The volume is calibrated and known at every point of the Petri dish.

Dry medium culture plate (MC MEDIA PAD® or 3M™ Petrifilm™)

• Ready to use — reduce or eliminate time-consuming agar prep
• Proven testing methods for consistent, reliable results
• Compact size uses less storage/incubator space

These methods serve as a convenient method for the rapid routine testing of microbial contamination of raw and in-process food and beverage materials, and finished products. They are pre-sterilized, ready-to-use dry culture device, simplifying testing and minimizing the quantity of waste.

Cytometry-based methods

It can be used to screen UHT products. This method uses a fluorescent labelling technique to detect viable cells directly in liquids by flow cytometry. The technique is relatively sensitive and has the potential to reduce the pre-incubation time of samples significantly. It can be applied to a range of non-filterable liquid food and beverage products and a protocol for sterility testing of UHT products has been developed for food manufacturers.

Bioluminescence (ATP, CO2..) 

One of the most widely used rapid methods for detection of contamination in UHT products is ATP-bioluminescence. By using a luminometer to detect light produced from microbial ATP in a reaction catalysed by the enzyme luciferase, it is possible to detect quite low levels of microbial cells in the sample, provided that it can be pre-treated with reagents designed to reduce background levels of non-microbial ATP in the sample. The method can be used as a presence/absence test for screening large numbers of UHT treated food and beverage samples after a considerably reduced pre-incubation time.