Bacterial pathogens in food and water cause more than 76 million infections per year in the US, which have symptoms ranging from mild gastrointestinal discomfort to severe illness and even death. Accurate detection of these pathogens is essential for avoiding infection. Although molecular and immunological detection methods have progressed, they do sometimes fail to identify toxic bacteria: those that rely on specific known DNA or protein sequences may not detect newly emergent or mutated bacteria. At the other end of the spectrum, existing detection methods may also give false positive results, prompting costly recalls and public distress. This is because the techniques cannot distinguish between live versus dead bacteria and cannot directly evaluate toxicity, only bacterial presence. In addition, many current approaches are time-intensive and expensive.

Now, a group of scientists led by Janine Trempy (Oregon State University, Corvallis) has identified a cell-based 'biosensor' that can detect toxins from foodborne bacterial pathogens. The new technology in food safety testing uses pigment-bearing cells called erythropores from Siamese fighting fish (Betta slendens). In response to potentially harmful environmental conditions, including bacterial toxins, the pigment in erythropores redistributes in a characteristic pattern. The pigment shift is quick, can be easily observed using low-power microscopy and can be quantified to describe the intensity of the stimulus (Microb. Biotechnol. 1, 425–431; 2008).

Trempy et al. first tested erythropore response to three types of Bacillus bacteria: B. cereus, which can cause vomiting and diarrhea; a B. cereus variant engineered not to produce toxin; and B. subtilis, which is not pathogenic. They observed the pigment shift only after exposing erythropores to toxic B. cereus. The group next assessed whether erythropores responded similarly to other bacterial pathogens: Clostridium perfringens, Clostridium botulinum and Salmonella enteridis. In each case, they observed a pigment response after exposing erythropores to the pathogens but not after exposing them to culture media alone (as a negative control).

More studies are needed before the erythropore method can be used commercially, including an assessment of its ability to detect other potentially toxic bacteria, such as E. coli O157:H7 and Listeria. But the technology holds promise for improving food safety testing and effectively protecting consumers from foodborne bacterial infections. “When this new technology is commercially available, we should be able to provide a higher level of assurance to the consumer while avoiding the waste of millions of dollars worth of food that is suspected of bacterial contamination, but actually is safe,” said Trempy.