Pathogen Detection at the Speed of Light

Many people believe nothing is certain in life but death and taxes. Daniel Y.C. Fung, PhD, professor of food microbiology at Kansas State University, adds another certainty to the list: “Food processors must get accurate results from tests to detect pathogens in raw materials. This holds true regardless of the technology employed, the time involved, or the cost. A rapid test giving bad results is not good whatsoever.”

Accuracy may be the top priority of microbial testing, but in light of the fast-paced global food system, speed is critical to every processing plant’s efficiency and profitability. While there are still no magic bullets delivering immediate results, there are many new and exciting rapid methods to test for bacteria, yeast, and molds in raw and processed food samples, Dr. Fung says. “Different microbiological tests measure different attributes of the cell mass, numbers, metabolites, and genetic materials, so it is really difficult to single out the significance of one test over another.”

Scientists currently rely on two major technologies for microbiological testing, molecular and immunological; both are considered highly accurate and fast. Of these, polymerase chain reaction (PCR) and immunoassays are the key methods available, respectively.

“Real time PCR systems and multiplex PCR systems offered by several high-tech companies are making great advances in rapid identification of pathogens,” Dr. Fung says. “A number of eight-hour tests are on the market for a number of pathogens, including E. coli O157H:7, which provide results during one work shift.” Dr. Fung himself developed what’s known as the Fung Double Tube (FDT) system, a six-hour test that has been used to detect Clostridium perfringens in ground beef.

Micro Hits the Big Time

The development of such tests is an indication of the market’s vitality. According to Food Micro—2008 to 2013, a market report published by Strategic Consulting, Inc. (SCI; Woodstock, Vt.), over 738 million food industry microbiological tests, with a market value exceeding $2.06 billion, were completed in the global market in 2008.

“The food sector represents the largest market segment within the industrial microbiology market…almost 50% of the total market,” says Thomas Weschler, MBA, SCI’s president. “The food sector is more than double the size of any other industrial segments, including the pharmaceutical, beverage, environmental, industrial process, and personal care products sectors.”

Since 1998, the market value for food microbiology has grown significantly, experiencing an annual growth rate of 8.7%. “Based on SCI research, the food microbiology testing market is expected to grow to 969.2 million tests in 2013, with a market value approaching $2.4 billion,” Weschler says. “This represents a projected annual growth rate of 5.6% in testing volume.”

Much work is being done to meet that demand. A variety of nanotechnology tests and procedures for image analysis of colonies are being developed, Dr. Fung adds. “These are not yet ready for commercial use but in due time may be available in food microbiology laboratories.”

There are some limitations with current rapid micro tests, Dr. Fung says. Some instruments and systems, like Fourier transform infrared (FTIR) spectroscopy, require only a few minutes to precisely identify a colony on an agar plate but are very expensive. Some rapid micro tests do not measure cell viability, an important factor in food microbiology. And some slow-growing organisms, such as yeast and mold, are difficult to detect using rapid methods.

“At least 50 companies throughout the world are working on a myriad of systems, and we are seeing new breakthroughs relative to rapid micro tests every day,” Dr. Fung says. “In the next three years, new ideas and procedures will emerge on many fronts.”

There will probably be more nanotechnology, microchips, and biosensor systems that can perform tests “faster and faster and cheaper and cheaper,” Dr. Fung says. And robotics will definitely play a big role.