23rd October 2014 Content supplied by: Hygiena international
Simple Enterobacteriaceae Test Results in 1-7 Hours
The MicroSnap product range is simple rapid test for bacteria giving results in the same shift, and the range is extended to include Enterobacteriaceae. The measurement of Enterobacteriaceae is a useful indicator of surface hygiene and product quality in the manufacture of heat processed food. Simple, rapid tests such as the specific ATP test system (MicroSnap EB) provides results in a working shift of <8 hours. The test has many applications and a wide dynamic range thus saving time and money and providing an effective tool for routine testing in production facilities.
The test can be applied to solid surfaces for environmental monitoring as well as raw material or finished product testing. It has an excellent agreement with cultural plate count methods and has a huge dynamic range of 1 to 10,000 bacteria in a single test device such that it can be used for presence / absence test or enumeration purposes. This means that less sample preparation or dilution is required thus saving time, labour and material costs as well as minimising the requirements for laboratory facilities.
MicroSnap EB (Enterobacteriaceae) is a simple two-step test procedure with a total time to result of 7 hours 15 seconds. The sample can be either a surface swab or 1ml liquid sample or food suspension that is mixed with a proprietary enrichment broth in an all-in-one device and incubated for 7 hours at 37°C after which a 0.1ml aliquot is transferred (using the device itself) to a specific end detection device for measurement in the EnSURE luminometer giving results in 15 seconds. The specificity of MicroSnap EB was determined by measuring its ability to detect 39 different bacteria in pure culture (22 Entero’s and 17 Non-Entero bacteria). Both the inclusivity and exclusivity were measured at 95%.
The output of MicroSnap EB is directly related to inoculum size such that greater the number of bacteria to shorter the time to detection. Table 1 shows a typical result (i.e. E. coli) in that ~10 Enterobacteriaceae were detected after the recommended 7 hour incubation. The dynamic range of the single test device is 10 – 10,000 bacteria per ml (or swab) thus negating the need for serial dilutions saving labour, materials and time. Conversely a shorter detection time can be set according to the desired specification e.g. 100 Enterobacteriaceae can be detected in 5 hours. Similar results were obtained for other key organisms including Cronobacter sakazakii.
The indigenous population in ground beef, salad leaves, raw milk, and ground raw chicken and raw prawns was measured by MicroSnap EB and compared to both VRBGA Pour plate methods and PetriFilm. Figures show the results for all food types and >200 test results to demonstrate a close agreement between MicroSnap EB and VRBGA pour plate method. There was also a high correlation coefficient ranging from 0.902 to 0.978 for each of different food types. A similar close agreement was obtained between MicroSnap EB and PetriFilm.
Certain samples can provide additional challenges due to the requirement to detect low levels of contamination and the physical / chemical effects of the sample itself. A successful test procedure was developed to detect the presence or absence of Enterobacteriaceae in 1ml of milk by modifying the enrichment conditions and incubation time. Adding 1 ml milk directly to 9ml of the Enhanced EB Enrichment Broth and extending the incubation period to 8 hours enables the sample effects to be reduced, very low numbers of bacteria to growth to detectable levels giving a dynamic range of 1 – 10,000 /ml. There was a good correlation (R2 = 0.904) compared to the traditional VRBGA method. In addition, the Enhanced EB Enrichment broth can also be used in conjunction with the MicroSnap Coliform and E. coli detection devices to verify the presence of these bacteria in 10 minutes following a positive result from the MicroSnap EB Enterobacteriaceae device.
Further information on MicroSnap is available on request to: Hygiena International Ltd Unit E 3 Regal Way Watford Hertfordshire WD24 4YJ
Tel: 01923 818821 Fax: 01923 818825
Date Published: 23rd October 2014
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