Question

Describe a situation where GBS Real time PCR would be preferred over traditional culture methods?

Answer 1

1.Knowing what to look for can be tough when it comes to TCM. While some tests are cut and dry — the organism either grew up or it didn’t — others require a bit of interpretation in order to be correctly read. Bacterial identification is an art form that can take years to perfect.
Until recently, Real-Time PCR has been much the same, requiring a seasoned eye with the technical skills to interpret results. However, as science melds with technology, new instruments such as the Hunter® greatly simplify the process and can consistently and automatically interpret the results.

Real time PCR is preferred over traditional culture method for better interpretation of result.

2.Bacteria grow on their own schedule; they don’t care about your company’s bottom line. More time spent waiting for results means more time a product spends in a holding pattern – this can be a significant cost and logistical issue for many products.TCM can take anywhere from 3 to 7 days for the most common food contaminants, while Real-Time PCR—including primary enrichment—can often be run in 10-24 hours.

3.There’s always one oddball out in a crowd, and bacteria are no different. There’s always one cell that just won’t conform to the standardized norm for a species—an E. coli that doesn’t metabolize lactose, or a Citrobacter freundii that no longer produces hydrogen sulfide. Because many of the traits that TCM look for are considered non-essential traits by the organism in question, there’s always the possibility that a pathogenic organism could be missed even by the most seasoned technician.
Real-Time PCR, on the other hand, usually hunts for highly conserved genes or essential genes that the cell would likely die without were they damaged or mutated. This allows Real-Time PCR to detect even those non-conforming organisms.
And because of the technology behind Real-Time PCR, many of the new instruments feature automatic electronic report-generating. Simply print it out and store for your records. No more worrying about incomplete record-keeping or trying to decipher Ted’s chicken-scratch.

4. At first glance, the amount of waste each test generates per sample doesn’t seem like an important concern, but it is. Consider this: each pound of waste generated has to be disposed of properly. This could require treating with household bleach or autoclaving in some cases. And because TCM often require both the primary and secondary enrichment to be plated in replicates of 5, all of those plates add up to quite the pile. For example, to test one slice of deli turkey for Listeria monocytogenes, two different broth media and 24 plates (of 3 different types) are required. And that doesn’t even count the biochemical test plate! Imagine running even just 20 samples a month.
Because Real-Time PCR can hunt for the correct DNA segment without all the trial and error, there is substantially less waste to be considered; typically only a few small tubes beyond the primary enrichment.

5.It’s not just the cost of reagents that needs to be considered. We’ve already touched on the fact that TCM require a more advanced skillset, and that can translate into higher wages and more cost per sample. Also, we’ve talked about how much time is taken by each sample, which pulls your staff from doing other important tasks, and the differences in the amount of reagents needed. Sure, a single plate may cost only $0.25, but when you’re going through 24 at a time, that can add up quickly. It is estimated that, even with the increased cost of the technology, PCR is 38% less expensive to run than TCM. See Real-Time PCR for the Detection of Salmonella.
Perhaps most important to consider is the cost of delaying the clearance of food products before they can be shipped to stores and consumers. Waiting for a negative result from TCM can mean reduced remaining shelf-life for the product and increased warehousing costs. It costs a lot to keep huge amounts of food refrigerated, or especially frozen! Real-Time PCR means faster release of product, which decreases your bottom line.