Bio-Rad targets Enterobacteriaceae detection in hours

By Joseph James Whitworth contact

- Last updated on GMT

Bio-Rad's iQ-Check Enterobacteriaceae real-time PCR detection kit
Bio-Rad's iQ-Check Enterobacteriaceae real-time PCR detection kit

Related tags: Polymerase chain reaction

Bio-Rad Laboratories has introduced a real-time PCR kit to detect Enterobacteriaceae in three hours following a single enrichment in non-selective buffered peptone water.

The iQ-Check Enterobacteriaceae Kit uses a system of primers and probes for high specificity to detect Enterobacteriaceae in infant formula, related raw ingredients and environmental samples.

It is designed as a multiplex reaction that includes an internal inhibition control that is amplified in parallel with the target DNA.

The iQ-Check Free DNA Removal Solution completes the method by removing free DNA from food and environmental samples.

Enterobacteriaceae used as indicators for hygiene process criteria

The test is not third party validated but the firm is working on ISO16140:2016 backing for 2018.

Jean-Philippe Tourniare, international product manager with Bio-Rad's Food Science Division, said it is for use at the production stage of the supply chain.

“In terms of limit of detection, it's very similar to the one obtained on iQ-Check Cronobacter methods on milk powder with LOD 0,8 [0.5;1.6] (CFU /30g).”

Tourniare added targets are infant formula manufacturers (baby <six months) with or without probiotics (10g sample), raw components (starch, protein extract, additives, etc) and samples of production environment (dusts, milk powders, etc).

Enterobacteriaceae are often used as indicators for hygiene process criteria. They are a large family of gram-negative bacteria that includes food pathogens like Salmonella, Cronobacter or pathogenic E. coli.

For thermally processed food or ingredients, quantification of EB provides an indication of efficiency of inactivation treatment and a guide to post-process recontamination.

Standard culture-based methods

Bio-Rad said testing of total EB based on the standard culture-based ISO 21528-1 method is labour intensive and requires at least two days for screening of negative samples.

Tourniare said action taken when a positive is found depends on the user and their policy and risk analysis and if it's related to environmental monitoring, raw material or finished product testing.

“In the case of positive PCR, some will discard the product, some others will perform confirmation, also including the tests for pathogens. (a little like Listeria spp approach vs Listeria monocytogenes approach, screening for Listeria spp, and if it is positive then re-test for Listeria monocytogenes).”

Bio-Rad offers reagents such as enrichment media, PCR kits, confirmation agars, PCR detection systems and software for automated analysis specific for each test.

The iQ-Check Enterobacteriaceae Kit can be used for up to 94 samples. Reactions can be run on low- or high-throughput Bio-Rad instruments depending on the laboratory’s needs.

Different iQ-Check assays can be run in parallel on the same plate using the iQ-Check Prep Automation System.

Salmonella test gets AOAC OMA validation

Meanwhile, Bio-Rad’s iQ-Check Salmonella II real-time PCR Kit has been validated by AOAC.

The validation is for a First Action Official Method of Analysis to detect Salmonella spp in raw meat in 12 hours and 20 hours for all other samples, including food and environmental surfaces.

As part of the validation, Bio-Rad did a collaborative study evaluating reproducibility and performance of the kit with dry pet food and milk chocolate due to their large presence of inhibitory compounds.

The Official Methods of Analysis (OMA) program evaluates analytical methods in chemistry, microbiology and molecular biology.

Jean-François Chauvet, Bio-Rad VP and general manager of the Food Science Division, said: “The OMA program is designed to identify the most reliable methods, ensuring that investigators in a wide range of industrial applications can use them to test with confidence.

“By selecting challenging matrices with large sample sizes for this validation, we have demonstrated the robustness of the method.”

The iQ-­Check Free DNA Removal Solution protocol is also part of the validation. This method removes free DNA from food and environmental samples prior to PCR analysis without the need for reagents such as ethidium or propidium monoazide.

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