Food Safety Magazine, April/May 2012

will detect both eae and stx virulence factors in addition to determining the presence/ absence of specific serotypes of E. coli that are known to be pathogenic STEC—E. coli

O26, O45, O103, O111, O121 and O145. The challenge of numbers is compounded by the mechanical/physical limitations of the two most widely used and reliable rapid testing methods: polymerase chain reaction (PCR) and immunoassays. Quite simply, the number of factors to be tested exceeds the capacity of familiar PCR and immunoassay technology to provide results in a one-step test.

Several test kit manufacturers have been hard at work overcoming these challenges to provide the industry with reliable, easy-to-use, accurate test kits (see “Challenges for Non-O157 STEC Testing,” p. 34). We can expect in the months and years ahead that additional improvements will become available with the trend toward increasing the capacity to test larger numbers of genetic targets in a single test and sample-preparation enhancements that will increase speed and accuracy.

Today, test kit manufacturers have adopted a stepwise approach of detecting virulence factors stx and eae and sequentially testing presence/absence of O26, O45, O103, O111, O121 and O145. Flexibility in testing arrangements may allow

“Combined virulence
factors within pathogenic
STEC are the building
blocks that make this
pathogenic STEC the
deadly monster
that it is.”

for identifying O factors by either immunomagnetic separation or PCR and then virulence factors by PCR. Some kits offer the flexibility to test for O factor first and then to test for stx and eae virulence. Hopefully, your work of evaluating test kits and selecting the best method for your needs (see “Choosing a Non-O157 STEC Test,” p. 36) will be easier now that we have reviewed the details of how these kits work and the challenges of testing non-O157 STEC. n

Jim Byron shares his extensive knowledge and
diverse experience gained as an executive in the
water, chemicals, food testing laboratory and test
kits business. Byron was recruited to a leadership
role in biotechnology and food safety in 2005.
His scientific work in close association with food
industry leaders, exposure to production systems
and strong business foundation allow Byron
to provide clear and useful information about
Listeria testing to managers in today’s food
production environment. He can be reached at
484.356.7283 or jb@xgenex.com.