Pathogen Detection at the Speed of Light

More research will help a new generation of microbiologists develop new and exciting rapid testing tools, Dr. Fung says. “It is important for all players in this field to stay positive and work on the issues with patience, openness, and optimism.”

Demand Drives Growth

Driving this worldwide development and growth is an increase in food consumption, consumer demand, industry food safety priorities, and regulation, Weschler says. The acceleration of the conversion of traditional microbiological testing methods to rapid methods is a function of those phenomena. It’s no surprise that, despite the higher cost per test, these newer methods are being used more frequently; compared with traditional testing, they provide faster results and/or ease of use benefits.

Nonetheless, traditional methods still account for approximately 58% of the microbiology tests performed worldwide in the food market. Their rapid counterparts—including convenience-based, immunoassay-based, and molecular-based methods—account for 42%. In fact, over the last three years, food micro tests utilizing rapid methods have increased by 37% to 307 million tests, up from 224 million in 2005. Some 80% or more of all tests are run to determine non-pathogens or indicator organisms.

“By 2013, much will have changed,” says Weschler. “Traditional methods will still be the predominant ones used, accounting for 491.2 million tests. However, traditional will represent only 50.7% of all tests conducted, which is approximately an 8% decrease based on percentage of tests performed.”

All types of rapid methods will make significant gains in usage during the coming five-year period, Weschler adds. “When combined, the annual test volume of rapid methods will increase by over 55% from current levels and reach 478 million tests in 2013. The gain in market value for rapid methods will be even more pronounced than the testing volume increases, since the rapid methods have much higher average prices per test than traditional methods.”

Roadblocks to Progress

Currently, progress with raw material testing is limited because of the required enrichment step, the time required to grow pathogens to detectable levels. In most enrichment steps, it typically takes 10 to 24 hours or longer to identify pathogens. Ideally, pathogens should be identified in eight hours or less; in a perfect world, the task could be slashed to minutes, even seconds.

Cost is another limiting factor with some rapid test products, according to J. Stan Bailey, PhD, MS, who spent 34 years as a research food microbiologist with the U.S. Departments of Agriculture’s (USDA) Agricultural Research Service. Dr. Bailey joined bioMerieux, Inc. in January as director of scientific affairs for industry. For 25 of the last 28 years, he has served on the faculty of Dr. Fung’s annual two-week rapid testing methods workshop.

“At first glance, some rapid and automated kits may seem expensive, as much as $10 to $15 per test, but you have to be mindful of the total costs of a microbiological test,” Dr. Bailey says. “Total costs of a conventional test include the costs of media and disposable plastics as well as the labor required for media preparation and reading and recording the results.”

Other factors drive the use of commercial test kits, Dr. Bailey says. These include better quality control, consistency of results from one sample batch to the next, time savings, and International Organization for Standardization or Association of Analytical Communities certification and documentation.

Sample handling has a major impact on the success of any test, rapid or conventional, Dr. Bailey says. Much work is being done to improve sample handling, he points out, including advances in concentration techniques, which improve the sensitivity of pathogen assays.

“For the past 20 years we’ve seen a pretty strong movement toward the use of automation to detect pathogens and indicator organisms,” Dr. Bailey says. “Almost all laboratories are being asked to do more with less resources, and the best solution to this pressure is better automation. One of our biggest needs is a rapid test to detect and count yeasts and molds in order to determine shelf life and spoilage potential.”