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Pathogenic Bacteria Testing Using Enzyme Detection Technology

Wed, 03/30/2011 - 4:49am

ATP assays require there be 10,000 to 100,000 bacteria present to produce enough ATP to result in a positive detection of bacteriawhich means it may miss the presence of bacteria in smaller quantities.A positive ATP test only confirms that organic matter is present and does not necessarily indicate the presence of bacteria. Because it tests for the presence of ATP, it cannot be used on food since food is organic. Additionally, the ATP assay cannot detect bacteria within Biofilm, which is a sticky byproduct of organisms that can hide live bacteria.

 

A culture assay is a laboratory test that determines what bacteria are present. Culture assays require the sample be incubated, typically 24 to 48 hours, to give bacteria a chance to grow in order to detect its presence. This requires sending the sample to a laboratory. The need for lab work increases the cost of testing as trained technicians and expensive equipment is utilized. Additionally, shipment to a lab can incur costly delays and possibly increase the chance of foodborne contamination should infected food slip through the system.

PCR is an assay that uses DNA to test for various bacteria. The process amplifies a piece of DNA generating millions of copies which takes between 12 to 26 hours. PCR assays, require the customer to ship the sample to a lab and also require a trained technician using specialized equipment to process the test. The test itself consists of several steps which must be followed exactly to achieve accurate results, adding to the costs. PCR assays take between 8 to 20 hours.

These existing technologies are ineffective for food producer’s purposes and result in food contamination, illness, loss of revenue and much more. 

Enzyme research has led to the discovery of specific enzymes associated with many different microorganisms. This made possible the development of proprietary substrates that can identify and link to specific enzymes given off by specific bacteria. Tests have been developed to utilize these proprietary substrates which, when hydrolyzed by an enzyme, produces a fluorescence that can either be read by a fluorometer or by adding a reagent to produce a colormetric reaction. This is represented in the diagram, and is referred to as the “Lock & Key Model of Enzyme Specificity.”

Other diagnostic systems must find the bacteria cell itself by growing the sample in cultures, or replicating DNA utilizing a PCR/NAAT system. These methods take more than a day to complete and require trained technicians and expensive equipment. Detecting the presence of enzymes is much faster given the abundance of enzymes being given off.

Enzyme Detection kits can be used in the field to test surfaces of equipment and foods. The tests confirm the presence or absence of bacteria with results on the spot in 20 minutes. The tests are easy to perform, require no extra equipment, and also detect bacteria hiding in Biofilm. Accuracy is greater than 98 percent if more than 1,000 organisms are present. Because they are inexpensive, fast and easy to use, more frequent monitoring and testing can be performed.

Manual strip and swab kits are available to test for total organism counts (including bacteria, yeasts and molds) and gram negative bacteria (harmful bacteria such as E. coli. and Salmonella). Each uses reagents that produce a chemical reaction in the presence of enzymes. This reaction causes a color to appear on the swab or strip.

A fluorometer test is a handheld digital device that can detect very low levels of bacteria (as low as 1 CFU per 100 ml of sample) in a matter of minutes. The meter is available to test liquids such as water, milk or beverages. For testing food or surface samples, the assay requires samples from an emulsion or a swab. The fluorometer utilizes proprietary fluorogenic substrates which, when hydrolyzed by a specific enzyme, produces a fluorescence that is read by the fluorometer.

Fluorometers are available for detecting total organisms, gram negative bacteria (Enterobacteriaceae), E.coli, Enterococcus, Fecal coliform and Salmonella.

Bacterial enzyme detection assays have many benefits over standard culture, ATP and PCR assays, including faster speed, ease of use, higher accuracy, lower cost, and the ability to detect bacteria in Biofilm. These assays provide results in as little as 20 minutes, where culture or PCR tests may take anywhere from 8 to 48 hours. The results are available in the field and do not require shipment to a laboratory. With results available in 20 minutes, these tests improve quality control procedures and decision-making in an industry where time spent waiting decreases shelf life and revenue. 

Culture or PCR assays utilize specialized equipment and trained technicians, whereas enzyme assays do not. This makes enzyme testing an effective low cost screening tool for food handlers. Enzyme detection assays have an accuracy rate greater than 98 percent.

Culture and PCR assays are expensive, slow and cumbersome. ATP assays are not reliable indicators of live bacteria. Using enzyme detection for identifying bacteria in the field provides an accurate, quick and inexpensive way to screen for bacterial contamination. With enzyme detection tools, users can test more often, thereby greatly increasing the success rate of catching bacterial contamination before it finds its way to the consumer.

More information on enzyme detection kits is available from DeltaTRAK, Inc., a leading innovator of Cold Chain Management and Food Safety Solutions. Contact DeltaTRAK at marketing@deltatrak.com or (800) 962-6776.

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