Fighting Against Food Pathogens

MALDI-TOF. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry can determine the unique proteomic fingerprint of a bacterium relatively quickly and inexpensively. It compares the bacterial protein profile obtained from a culture to a library of known patterns. “Typically, no more than an isolated colony from a culture plate or a small aliquot from a broth is required,” explains Daniele Sohier, PhD, business development manager, industrial microbiology and diagnostics at Bruker Daltonik GmbH. “The entire method takes only a few minutes for a single sample, with results up to 24 hours faster than traditional methods,” she tells Food Quality & Safety.

Bacteriophage-based assays. Bacteriophages are viruses that infect bacteria. Because they are highly specific, interact quickly, and are harmless to humans, bacteriophages can be incorporated into novel assays and biosensors to detect, and in some cases even eliminate, foodborne pathogens.

Novel biosensors. These biosensors use biological elements, such as small molecules, proteins, or cells attached to a sensor surface to recognize or bind to specific targets or components of bacteria. Detection methods include label-free sensors, immunosensors, fluorescence-based, and carbon-nanofiber sensors.

Rapid microbial detection methods. These typically use fluorescent DNA markers to identify pathogens rapidly and accurately. These culture-independent platforms use fluorescent in situ hybridization, fluorescent microagglutination, and filter cytometry. Other rapid approaches include low-cost test strips to indicate the presence of a particular pathogen within hours. For example, paper- or film-based assays using stencil-printed carbon electrodes are able to detect E.coli and other bacteria within 4-12 hours.

WGS Still King

Despite these and other advances, WGS or next-generation sequencing, remains the gold standard for pathogen detection because of its high precision. As the cost declines, officials expect small WGS sequencers to proliferate among state and local public health agencies, as well as among private labs and manufacturing companies.

“We are looking at some very small sequencers that could fit in the pocket,” says Marc Allard, PhD, CFSAN’s research area coordinator for genomics. “We could have a lab in a briefcase that could go out to the consumer safety officer and actually do field testing. This is the future vision,” he says.

But because of its current complexity, cost, and other requirements, the food industry has largely steered clear of WGS. “The science and technology behind WGS are new and might seem a bit more complicated than the ones that have been in use by the industry for many years,” said Behzad Imanian, PhD, WGS project leader at the Institute for Food Safety and Health (IFSH) at Illinois Institute of Technology.

The amount of data produced by WGS can be “overwhelming,” Dr. Imanian told an IFSH symposium in May. The data analysis requires a proficiency in bioinformatics, which could be problematic for industry, while data interpretation “is far from simple, even for trained bioinformaticians,” he added. Thus, while U.S. and international food safety regulators are increasingly embracing WGS, the food industry has been reluctant. A notable exception has been the Consortium for Sequencing the Food Supply Chain, an initiative started in 2015 by IBM Research and Mars Inc. Recently joined by Bio-Rad Laboratories, the consortium is sequencing the genetic material of food and soil samples in order to create a “microbial baseline” to better understand the factors behind contamination and foodborne disease.

Interagency Collaboration

In 2011, the CDC, FDA, and USDA’s Food Safety and Inspection Service established the Interagency Food Safety Analytics Collaboration (IFSAC) to improve coordination of federal food safety analytic efforts and address cross-cutting priorities for food safety data collection, analysis, and use. In addition to Campylobacter and Salmonella, IFSAC’s efforts have been directed at E. coli and Listeria monocytogenes.