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How South à£à£Ö±²¥Ðã State University's Animal Disease Research and Diagnostic Laboratory plays a critical role in keeping South à£à£Ö±²¥Ðã's food supply safe. 

When Zachary Lau checks out at a grocery store with a cart full of beef, chicken and seafood, he usually gets some inquisitive looks and questions.

"Sometimes I'll get asked if I'm an athlete with all the protein," Lau explained. "I also usually get a few interesting looks when I'm loading meat into a cooler in the trunk of a state vehicle."

As a senior microbiologist in South à£à£Ö±²¥Ðã State University's Animal Disease Research and Diagnostic Laboratory, Lau is charged with visiting different grocery stores in different areas of the state each month, buying up various cuts of meat, chicken and seafood. The grocery store haul is then brought back to the lab, where the food is tested for the presence of bacteria.

"We test the meats for the presence of Escherichia coli (E. coli), Salmonella and Listeria — things of that nature," Lau, an SDSU grad, said. "We are looking for antimicrobial resistance in retail meats and seafood."

Lau's work is part of a national network of food surveillance and is one of the ways South à£à£Ö±²¥Ðã's unique food safety laboratory — the Animal Disease Research and Diagnostic Laboratory's Food Safety Microbiology Lab — works to keep the state's food supply safe.

Food safety in the ADRDL

Each day, the Animal Disease Research and Diagnostic Laboratory receives shipments of meat samples from butchers and processing facilities around the state. For facilities that aren't large enough to be inspected by the U.S. Department of Agriculture, the South à£à£Ö±²¥Ðã Animal Industry Board provides inspection services and affiliated testing is done through the ADRDL.

Meat from individual facilities is tested on a quarterly basis, but the number of meat-producing facilities in the state makes meat testing a daily activity.

It's not just meat the lab is testing. The facility also tests a variety of farmer's market-type products — like canned jellies, jams and pickles — as well as raw milk.

Kara Hendrickson-Guttum is a research associate II in the lab. As she explains, once a sample is received, it undergoes an overnight enrichment process. This process starts with the addition of liquid media, a solution that facilitates bacterial growth, to the sample.

"The overnight enrichment is critical as we must detect low levels of bacterial contamination.  Our specialized media allow us to target different organisms and enrich for detection," Hendrickson-Guttum explained.

The following morning, the team takes the enriched food and begins screen testing the sample. They are looking for the presence, or absence, of genetic markers of bacteria. This tells them if Salmonella, for example, is present in the sample.

The SDSU lab is looking for the most frequent causes of bacterial foodborne illnesses in the U.S.: listeria, E. coli, salmonella and campylobacter. While positive results are rare, they do happen on occasion.

"If we get a positive screen, we must do a cultural confirmation," Hendrickson-Guttum said. "We grow and isolate the bacteria from the sample to make an identification.�

This confirmation process provides an extra layer of security and ensures that false positives aren't reported.

"A molecular test on its own isn’t enough. We must isolate that organism from the product because if you've got a carcass hanging in a processing facility and they take action to reduce bacterial growth, it's possible the bacteria that showed up on the test was already killed during this intervention step," explained Laura Ruesch, a research associate III in the food safety section of the Animal Disease Research and Diagnostic Laboratory. "So, if we were to test and find DNA only, the bacteria could already be dead and not pose a risk to consumers."

Traditionally, when a positive sample is identified, the product is held until further testing is completed. The team will usually call whoever sent the sample informing them of a potential positive result. This prevents potentially harmful products from entering the food supply.

There are different levels of concern for different types of bacteria. The presence of salmonella in ground meat doesn't necessarily mean the product isn't safe to eat, as it is normally cooked prior to eating. But ready-to-eat products — like beef sticks — that test positive for salmonella are not safe to eat. The most alarming bacteria they detect are Shiga toxin-producing E. coli (STEC).

"There's no safe level with those," Ruesch said. "It's very dangerous and ingestion of as little as 10 cells can make a person very ill.  Law now states meat containing STEC is adulterated.â€�

An “adulterated" product is not safe for consumption and cannot be sold.

One of the biggest misconceptions with the food safety section of the Animal Disease Research and Diagnostic Laboratory is what they can — and cannot — do. As Lau explains, the scientists are strictly there for testing and do not have regulatory control.

"Our testing is really preventing a scenario from where a recall situation would happen," Lau added. "It's a preventative measure." This entire process is designed to prevent contaminated products from ever reaching the dinner table.

Technology has made food safer

Ruesch got her start in food safety while a student at SDSU. She started first in the molecular section of the lab. In her last year of college, Animal Disease Research and Diagnostic Laboratory leadership knew she had future career interests in microbiology.

"I had a semester left of school and the food safety position opened up," Ruesch said. "They held it until I graduated."

Ruesch graduated from SDSU in 2001. Since then, she has seen the technology capabilities of the lab vastly improve, from enzyme-linked immunosorbent assay (ELISA) to polymerase chain reaction (PCR) testing and to now even better technology, Ruesch said.

"Technology has really changed from the time I've been here," Ruesch said. "The accuracy of our tests is better. We can more quickly identify things that are important."

The technology has also made it so less false positives are reported, helping save producers money, Lau said.

"Our confirmation process is faster and more reliable," Hendrickson-Guttum added.

These improvements come at a time when, nationally, public confidence in the U.S. government's ability — specifically government regulators’ ability — to protect the food supply is at an all-time low, according to a September 2024 Gallup poll. Experts believe this might be due to a general decline in trust of government, science and expertise, but others believe it could be due to the headline-grabbing recalls from the past five years.

Regardless of the national public sentiment, food safety in South à£à£Ö±²¥Ðã remains strong — thanks largely to the lab's expertise and technology. The highly accredited Animal Disease Research and Diagnostic Laboratory must meet certain technology and equipment standards. In fact, the lab's technological capabilities are on par with federal food labs in the country and enable quick turnarounds on sample test results. This creates an extra layer of security around South à£à£Ö±²¥Ðã's local food supply.

National networks

Following the Sept. 11 terrorist attacks, the U.S. federal government enacted a variety of security measures to keep Americans safe. One of these measures was to develop a Federal Emergency Response Network, a program chaired by senior officials within the USDA and Food and Drug Administration to coordinate lab responses to food-related emergencies.

The Animal Disease Research and Diagnostic Laboratory joined the Federal Emergency Response Network in 2005 and has helped in various network-related efforts since then. This has included testing tomatoes and peppers during a widespread salsa recall in the late 2010s and high-profile political events.

The Federal Emergency Response Network hasn't been activated for a few years, and as Ruesch explains, it takes a very large recall or emergency situation for it to be activated.

The SDSU lab receives annual federal funding as part of the network, which allows them to sequence entire genomes for a program called GenomeTrakr. This sequencing is uploaded into a massive public database where FDA, USDA or Department of Health officials can map and track different organisms against each other.

"Our contribution to this effort includes whole genome sequencing of foodborne pathogens, expanding the public database which allows public health officials for real-time comparison and analysis that can aid with foodborne illness outbreak investigations," Ruesch said.

SDSU's Animal Disease Research and Diagnostic Laboratory is one of 172 Federal Emergency Response Network labs but is one of only 40 to receive microbiology cooperative agreement funding from the federal government, underlining the lab's strengths and capabilities.

The SDSU lab is also a part of the National Antimicrobial Resistance Monitoring System, a collaboration between the FDA, USDA, Centers for Disease Control and Prevention and state labs to screen for antimicrobial resistance. Since 2017, the FDA has provided funding to the ADRDL for screening retail meats and seafood for pathogens. Lau's grocery store runs are part of this work.

"The data generated by the NARMS is used by the FDA to make decisions about usage of antibiotics in humans and à£à£Ö±²¥Ðãs in an effort to maintain effectiveness of these important drugs," Ruesch said.

Including Animal Disease Research and Diagnostic Laboratory into these federal networks, as well as the capabilities for the lab to conduct diagnostic testing and research — all on a college campus — makes it one of the most comprehensive and unique laboratories in the U.S. There is maybe one or two other labs in the U.S. that have the same general structure and capabilities of the ADRDL, Ruesch said.

The uniqueness of the lab provides SDSU undergraduates with opportunities and experience while providing graduates with career options. But for the team of microbiologists, the best part of working in the lab is helping small-business owners around the state.

"Helping out producers and local small business owners who are trying to do something in their community is very enjoyable," Hendrickson-Guttum said. "Supporting them is worthwhile."

As Lau notes, the COVID-19 pandemic resulted in an influx of business at state meat processors due to temporary closures at the large federally inspected facilities.

“The closures resulted in a greater need for local processing and several new businesses needed our testing support," Lau said.

"We are big enough that we have all the technology that we need, but we’re not so big that we lose our connection to the food industry," Ruesch added.