Scientists develop “rapid” salmonella detector

A team of researchers have been working on a device that they claim can detect the presence of salmonella in food.

According to the team, the device is an “easy-to-use” colorimetric assay that is based on a novel nucleic acid probe, cleaved by an RNase enzyme specific to the salmonella species. The researchers have said that this specific enzymatic cleavage principle “made it possible to build a sensitive but simple and portable test system using colloidal gold”.

Noting that typically, food contaminated with salmonella is “usually only confirmed several days later when the bacteria are detected in microbiology laboratories by growing them in culture”, the scientists worked on developing a novel test system based on a hybrid DNA-RNA probe that specifically and rapidly detects salmonella, without the need for microbiological diagnostics or expensive analytical equipment.

The team at McMaster University in Hamilton, Canada used a multi-round selection process, and uncovered an artificial DNA-RNA hybrid probe that is a substrate for a salmonella-specific form of an RNase H enzyme.

Based on these findings, the team first developed a fluorescence-based assay on salmonella RNase H, and then extended the principle to a simple, portable salmonella assay based on a colloidal gold colorimetry.

“When the sample mixture contains salmonella, the upper layer is released thanks to the salmonella RNase H specifically cleaving the DNA-RNA linker probe,” explained the researchers.

“When the gold-containing solution is then drained onto an absorbent pad with a nylon membrane, a clear red spot indicates the presence of salmonella in the sample being tested.”

The team also tested the specificity of their system and have claimed that it did not falsely detect the presence of other bacteria containing RNAse H.

Stating that their testing system is “much less complex than other methods for detecting salmonella”, the team has also claimed that the method is much faster.

“In contrast to other methods, only one hour of incubation in a pipette tip is required for highly sensitive detection of salmonella, for example, in ground beef,” said the researchers.

Looking forward, the scientists have said that they envision developing more nucleic acid probes which can specifically detect other infectious pathogens such as E. coli.