Neogen develops method to detect Listeria spp., L. mono

Neogen’s One Broth One Plate workflow can be used to test food and environmental samples, and provides results in 48 hours - with enhanced sensitivity versus ISO 11290 methodology. The workflow has received NF validation and AFNOR certification.

The protocol has been NF certified for all food and environmental matrices according to ISO 16140-2 which assures users it performs as well or better than the gold standard method (ISO 11290). 

Neogen said in sensitivity studies for Listeria spp. and L. monocytogenes the number of positive deviations was higher than negative ones showing One Broth One Plate is more sensitive than the standard ISO method.

Currently, labs can choose from the ISO 11290 standard, chromogenic media, rapid protocols including ELISA, PCR and other molecular methods like Neogen's ANSR to detect Listeria.

EU legislation and indicator species​

Steve Chambers, Neogen Europe’s sales and marketing director, said to implement within a lab the minimum required would be to perform a verification on their own matrices.

“Some laboratories prefer to carry out a small validation in line with their own quality practices. In some cases, for pathogen detection, labs will have an accreditation body review their data from verification and validations to ensure they have been performed correctly,”​ he told FoodQualityNews.

“Listeria monocytogenes is covered under EU regulation therefore testing is mandatory. Listeria species is a food indicator and is therefore often covered under due diligence testing.  ​

“Since L. mono is pathogenic it's essential to test for. L species is also important as it can be used as an indicator of risk - if conditions allow for the growth of Listeria you could be at risk from L mono - this is especially useful for environmental monitoring.​”

Sometimes the ISO standard is required because of customer requirements, said Chambers.

“But also labs can respond better when they have a variety of methods to hand. Neogen and Lab M are in a position to offer a choice - whether you prefer classical or rapid methods,” ​he said.

“One Broth One Plate is a good solution where your lab is comfortable with plates and wishes to stay with classical microbiology - to move over wouldn't be a huge change for your staff but would give you results within as little as 48 hours where needed.​

“What is also helpful is that the enrichment used for One Broth One Plate is also used for ANSR Listeria species and L. mono so you can run both methods side by side with ease. One Broth One Plate can be used as confirmation for ANSR and vice versa.”​

Workflow specifics​

Chambers said it is the start of many collaborations between Acumedia and Lab M.

“The development of the workflow is especially meaningful to us, as it combines our Acumedia enrichment broth with Lab M’s chromogenic agar plates - a combination made possible by Neogen’s August 2015 acquisition of Lab M.” ​

The next release will be a chromogenic plate for Salmonella.

Primary enrichment in the workflow is Acumedia’s LESS Plus media, a selective enrichment broth for detection of Listeria spp. Manufactured using dehydrated culture media (DCM), LESS Plus medium is compliant to ISO 9001:2008.

The workflow’s agar plate uses Listeria Chromogenic Agar (LCA), a selective medium formulation compliant to ISO 11290-1:2014 according to Ottaviani and Agosti and performance compliant to ISO 11133:2014.

By using chromogenic and phospholipase enzyme reactions, the media allows for identification and differentiation of L. monocytogenes and Listeria spp. on one plate.

Neogen can supply the LCA media ready to use as part of Lab M’s Pinnacle pre-poured media range, which includes supplements with no need to weigh, cool or autoclave media.

The LCA media is available in DCM format, with additional supplements required, as part of Lab M’s Harlequin chromogenic media range.

“Lab M’s Pinnacle pre poured media reduces the need for in-house quality control as the Lab M pre poured media is quality control checked to ISO 11133 and under the scope of ISO 17025 (UKAS), but some labs may use DCM because they have a higher throughput and it can be more cost effective depending on throughput and sample type,”​ added Chambers.