Captivate O91 comprises magnetic particles coated with antibody designed for isolating E.coli O91 from food samples.
It separates E.coli O91 from background flora in a sample ensuring only organisms having O91 antigens are captured.
Foods most commonly tested for STEC include red meats, raw dairy products and vegetables.
IMS to help separate target organism from background flora
Ez Elmerhebi at Lab M said background flora can be drastically different depending on the sample.
“Raw and untreated products can contain high levels of non-target organisms, and the selective enrichment stage will help to select out gram positives,” he told FoodQualityNews.
“This tends to mean other enterobacteriaceae will be the greatest concern. This is where IMS can greatly improve detection due to the specific antibodies used that will allow the user to concentrate even low level target organisms.”
Captivate IMS beads work with food, animal feed, beverages, pharmaceutical or environmental samples.
Lab M’s first Captivate product, for E.coli O157, has been used by the industry for over 15 years.
Captivate O45 was unveiled around one year ago.
The firm said although E. coli O91 isn’t included in the US ‘big 6’ or the European ‘top 4’, the serogroup is one of the most common human pathogenic eae-negative STEC strains, and is seen as a threat in some European countries.
IMS increases sensitivity of the methodology and, in most circumstances, results can be achieved 24 hours earlier than using standard protocols.
Protocol and media
Samples are enriched for 16-24 hours and IMS takes one hour. Magnetic beads are plated onto agar medium and incubated for a further 16-24 hours.
The protocol for the range of E.coli IMS products is the same except for the final plating medium, said Elmerhebi.
“For Captivate O157 and O26, Sorbitol MacConkey and Rhamnose MacConkey respectively can be used to differentiate the target from other organisms,” he said.
“However, most of the other serotypes are not biochemically unique. Thus an IMS product with antibodies specifically targeted to the somatic (O) antigen - like the Captivate range - can be useful to capture and concentrate your target STEC.”
Captivate bacterial IMS kits can also serve as a capture tools for rapid detection systems.
“What’s interesting and sequentially dangerous about E.coli O91 is that, unlike other STEC, it commonly lacks the eae gene which is routinely used in molecular methods as a virulence determinant; thus it can often be missed with current molecular protocols,” said Elmerhebi.
“Using IMS to specifically isolate this serogroup, you can dramatically increase your chance of detecting this dangerous pathogen.
“It should also be remembered that IMS is included in reference methods for the isolation and confirmation of the key O groups, making IMS a critical tool when testing for any STEC serogroups.”
Lab M also revealed Cedarlane as distributor for North America during the IAFP trade event.