Food Protection Trends - July/August 2024 - 300

GENERAL INTEREST PAPER
Discrepancies in the Microbiological Analysis of Foods:
Causes and Resolutions
J. David Legan,1* Laurie Post,2
Christina Barnes,3
Sophie Pierre,10
Purvi Chatterjee,6 Nisha Corrigan,7 Daniel R. Demarco,8
Ryan D. Maus,2
1Eurofins Microbiology, Madison, WI 53704, USA
2
3
4
Deibel Laboratories Inc., Niles, IL 60714, USA
Neogen, Oakdale, MN 55128, USA
Midwest Laboratories, Omaha, NE 68144, USA
5Cargill, Inc., Wayzata, MN 55391, USA
6ACRL LLC/WTI, Inc., Jefferson, GA 30549, USA
7
Hygiena, Camarillo, CA 93012, USA
Amanda Brookhouser-Sisney,4
Thomas Hammack,9
Patricia Rule,11 Nikki Taylor,12
W. Evan Chaney,5
Kristen A. Hunt,2
Alexandra Tudor,13
and Julie Weller7
8Eurofins Microbiology, Louisville, KY 40299, USA
9
Center for Food Safety and Applied Nutrition,
10
11
12
13
U.S. Food and Drug Administration, College Park, MD 20740, USA
Bio-Rad, 92430 Marnes-la-Coquette, France
Micro Rules LLC, O'Fallon, MO 63368, USA
bioMérieux, Inc., Hazelwood, MO 63042, USA
Bio-Rad Laboratories, Hercules, CA 94547, USA
SUMMARY
This article discusses the types of problematic results that
can arise during microbiological testing of food and food
processing environments, which potentially undermine the
effectiveness of food safety programs. It outlines steps for their
resolution and offers readers a structured approach for evaluating
the multiple contributing biological, technological, and
human factors. To assist in troubleshooting and identifying the
root causes of these problems it gives examples of 15 common
root causes. It also presents measures to prevent the recurrence
of discrepant and ambiguous results. These measures
are rooted in a robust laboratory quality system incorporating
validated methods, standard operating procedures, calibrated
equipment, maintenance of meticulous records, proficiency
testing programs, and continuing education opportunities
for laboratory personnel. In conclusion, the article advocates
for comprehensive risk assessment of problematic results and
offers actions to strengthen the application of microbiological
methods within food safety programs, in line with the U.S.
Food and Drug Administration's objective of preventing adulterated
food products from entering commerce.
OVERVIEW
Microbiological analyses of foods are performed for several
reasons, including the following:
* Verification of hazard analysis critical control points
or food safety plan preventive controls through testing
of plant environmental samples, in-process materials,
product contact surfaces, and finished products
* Detection of patterns and trends to illustrate process
control (20)
* For release of the finished product
* Demonstration of regulatory compliance or conformity
with customer specifications
* Troubleshooting a microbiological issue in the product,
process, or facility
300 Food Protection Trends July/August
* In response to a consumer or customer complaint
* During research associated with product or process
development
When performed and interpreted appropriately, microbiological
analyses generally deliver results upon which we can
act. However, the process involved is complex. Representative
samples must be prepared and analyzed by an appropriate
method that allows the target organism or organisms to
grow to detectable levels in suitable media. The detection or
enumeration technology must give a reliable signal. Finally,
any calculation based on that signal must deliver an accurate
result. Given this complexity, sometimes even validated
methods can yield results that may be inconsistent with prior
knowledge and results from other tests. In addition, results
can be reported as indeterminate or inconclusive by rapid
methods. Nonconclusive results make decisive actions difficult
to determine. In the case of discrepant results, further
analysis may be required.
Estimating the risk of such discrepancies is difficult. One
approach may be to look at data from proficiency schemes
collected over several years, because samples from these
schemes are inoculated, standardized, and presented to
multiple laboratories and analysts using various methods and
equipment. These data suggest a false-positive rate of around
4% and a false-negative rate that varies by pathogen, with
atypical strains and low concentrations of bacteria most likely
to be missed (1, 10).
This article presents a discussion of the types of discrepancies
that commonly occur in food and environmental
microbiological testing. Various root causes may exist for any
discrepant testing observation. Therefore, the potential scenarios,
causes, and resolution strategies are intended not to
be fully comprehensive but to provide a structured approach
to problem-solving. Figure 1 summarizes initial approaches to
the resolution of problematic results.
*Author for correspondence: Phone: +1 608.949.3076; Email: David.Legan@ft.eurofinsus.com
https://www.foodprotection.org/files/food-protection-trends/jul-aug-24-Legan.pdf
Food Protection Trends - July/August 2024

Table of Contents for the Digital Edition of Food Protection Trends - July/August 2024
