New Test Detects Salmonella in Food Faster

HOUSTON Researchers at Rice University, in collaboration with researchers from Thailand and Ireland, developed a biosensor that may make the detection of pathogens much faster and easier for food-manufacturers, according to a new study published in the journal Analytical Chemistry.

Unlike the current standard tests, which can take days to culture colonies of salmonella bacteria as proof, the Rice process delivers results within minutes from a platform that can be cleaned and reused. The technology can be easily customized to detect any type of bacteria and to detect different strains of the same bacterium, according to the researchers.

The process uses a set of "diving boards," or microcantilevers, each of which can be decorated with different peptides that have unique binding affinities to strains of the salmonella bacteria. When a peptide catches a bacterium, the cantilever bends ever so slightly, due to a mismatch in surface stress on the top and bottom. A fine laser trained on the mechanism catches that motion and triggers the alarm.

The system is sensitive enough to warn of the presence of a single pathogen, according to the researchers, who wrote that very low pathogen concentrations cause foodborne disease.

To characterize the peptides, researchers isolated bacteriophage viruses associated with salmonella through biopanning and phage display, a technique to study interactions among proteins, peptides and pathogens. They then derived peptides from the phages that would serve as targets for specific bacteria.

The Rice lab compared the peptides' performance with commercial antibodies now used for salmonella detection and found the peptides were not only more sensitive but could be used in a multiplexed cantilever array to detect many different kinds of salmonella at once.

"The peptides are very robust," said Sibani Lisa Biswal, Rice biomolecular engineer. "That's why a lot of people like them over antibodies. The peptides can handle harsher conditions and are much more stable. Antibodies are large proteins and break down more readily."

In an attempt to further reduce risk of salmonella outbreaks, the U.S. Department of Agriculture (USDA) and U.S. Food and Drug Administration (FDA) approved Micreos SALMONELEX as GRAS (generally recognized as safe) for use as an antimicrobial food-processing aid against Salmonella. SALMONELEX, which consists of natural phages against Salmonella that eliminate the bacteria rather than inhibit its growth, can be sprayed topically or added to chill tank water.