Real-time PCR assay for S. aureus

Staphylococcus aureus exist in air, water, milk, food, equipment and environmental surfaces. Foods often implicated in S. aureus contamination include those that require considerable handling during preparation are frequently. Culture-based screening procedures require a laborious plating and enumeration method followed by a coagulase reaction test, for results in three to five days or more.

The new system can produce next-day results after 20-22 hours enrichment and enable the presence or absence of S. aureus to be detected in less than 90 minutes processing time

Validated on powdered infant formula and ground beef it shows a sensitivity as low as 1 cfu per10-gram sample, and can also be used for threshold testing (>10 cfu/gram).

Developed in alliance with Applied Biosystems the assay uses probe-based chemistry and real-time PCR detection to detect very low concentrations of S. aureus in food samples. Using the power of the polymerase chain reaction (PCR), the system rapidly amplifies unique DNA fragments, when present, for quick and reliable detection of S. aureus.

BAX system assays simplify the method by combining all the PCR reagents you need into a single tablet, conveniently packaged inside the PCR tubes contained in each kit. Tableted reagents provide for minimal hands-on time, in addition to accuracy, long shelf life and consistency.

After enrichment, samples are lysed to break open the cell walls and release DNA. This lysate is then used to hydrate the PCR tablets. Processing in the Q7 unit takes less than 90 minutes for a full rack of 96 tests. Electronic results appear as positive icons if S. aureus is present. A table of results for each target also allows you to view the amplification plots for the target and the internal positive control. Data is LIMS-compatible and can be easily stored, shared or printed.

DuPont has also developed with Applied Biosystems BAX System for sampling Campylobacter, E. coli, Enterobacter and Listeria