When government and industry were looking for a way to identify more rapidly the presence of the pathogenic Clostridium perfringens bacterium in food and water, Daniel Fung of Kansas State University realized he had a potential solution on his shelf.
He applied what’s known as the Fung Double Tube method, which he developed decades earlier, and determined that the detection time can be reduced from about a day or two down to four hours. More work needs to be done to improve the process, but a successful effort would benefit food processors.
“In the meat industry and related food industries, the faster one can detect and enumerate live major pathogens such as C. perfringens, the faster corrective actions can be implemented or the food can be destroyed before reaching the consumers,” said Fung, a food science professor who researched the issue as a Food Safety Consortium-supported project. “The benefit of a rapid method to detect and enumerate live C. perfringens in foods in four hours is obvious.”
C. perfringens can cause poisoning through temperature abuse of prepared foods, usually meats and meat products. The Food and Drug Administration says small numbers of the organisms are often present after cooking and multiply to food-poisoning levels during cool down and storage of prepared foods.
Rapid detection of the pathogen would benefit not only food processors but also agencies that keep water supplies safe. Fung explained that Hawaii officials look for C. perfringens as an
indicator of the safety of recreational water.
“Hawaii is the only state that used C. perfringens as an indicator of fecal contamination in water,” Fung said. “If there was too much Clostridium perfringens, they’d close the beach. They’d been using the system for many years in the lab, but their system took up to 48 hours to get a count.”
That’s longer than an agency would prefer when public health is at stake. Several years ago, Fung met a Honolulu water microbiologist at a conference, when the subject came up. He explained the Fung Double Tube method for detecting pathogens and showed the lab personnel in Hawaii how to apply it.
The Fung Double Tube method is relatively easy to implement. The system uses one large tube and one small tube. Insert the small tube into the larger tube that holds a water sample. Then add a specially melted agar — a gelatin-like product used for solidifying culture media as a thickening agent — to create a thin layer between the two tubes that will grow C. perfringens. The unit is then placed in an incubator at 42°C.
“The system makes anaerobic microbiology very simple,” Fung said. “One can see a C. perfringens colony in the Double Tube in about four to five hours. We can know in five to six hours how many living colonies of C. perfringens per milliliter of water there are. That is a major improvement, and it’s so cheap.”
The system works well for water testing, but more research is necessary to prepare it for use in the food industry. Fung’s research team is examining how to apply it for use with ground beef so the meat won’t have to be incubated overnight before pathogen counts can be obtained.
“Then, if you have a high number of perfringens, the food should be red-flagged,” Fung said. “When we finish our comparisons, then we can tell the food industry that if you have the double tube and in four to five hours you see a black colony with fluorescence, then you can count that as perfringens.”