Detecting foodborne bacteria has never been easy. Pathogenic bacteria are often sparsely distributed throughout food batches and can be present in very low numbers in randomly collected food samples. Further, the diversity of normal flora found in various food matrices creates a complex and dynamic microbial ecosystem that could interfere with the detection of target pathogens. Microbial dynamics are also influenced by food’s microstructure and chemical composition, which adds additional complexity to the detection process. Consequently, the detection of foodborne pathogens requires, first and foremost, accurate and reliable techniques to effectively maintain food safety.

Conventional culture-based methods, which were developed and implemented several decades ago, continue to deliver a reliable but conservative solution, capable of detecting as few as one target cell per 25g to 325g food sample. These methods are still widely regarded as gold standards for detecting foodborne pathogens, due to their precision and accuracy; however, these traditional methodologies are time-consuming, taking more than a week to provide a final result. Moreover, each identified pathogen requires independent protocols, which is neither convenient nor compatible with today’s intense production needs.

To address the shortcomings of traditional detection methods, numerous molecular techniques have been developed and used effectively in the past decade to detect foodborne pathogens. The development of real-time quantitative polymerase chain reaction (qPCR) has revolutionized microbiological analysis by enabling the detection of pathogenic microorganisms in food without the need for the labor-intensive and time-consuming procedures of isolation and identification. This method has dramatically reduced the time-to-result, which is a critical performance standard used to evaluate the effectiveness of a detection tool, alongside assay sensitivity.

The qPCR method not only provides faster, more sensitive, and specific results than traditional PCR methods, but also offers the potential for multiplexing, which means it can simultaneously detect multiple pathogens in the same reaction, enhancing operational efficiency and reducing overall costs. Numerous food commodities, including shellfish, fresh fruits and vegetables, dairy, and meat products, have been found to be contaminated with multiple pathogens of concern, such as Salmonella enterica, Listeria monocytogenes, and Escherichia coli, along with diverse species of Shigella, Campylobacter, and Vibrio. Consequently, simultaneous detection of multiple pathogens on a single-assay platform aligns with contemporary food industry trends and could also mitigate industry and regulatory needs in the mandatory testing of food products for a range of pathogens prior to distribution.

The Enrichment Step

While the potential advantages of qPCR multiplexing may seem apparent, it’s important to consider the sensitivity of these detection platforms. To guarantee the achievement of legal limits (absence in 25g for most bacterial pathogens), an enrichment step using microbiological culture media is still required prior to qPCR detection. Integrating both traditional microbiological enrichment and molecular pathogen detection serves as a useful bridge that links traditional and molecular microbiology. This approach offers combined benefits while also reducing some of the limitations associated with each method.

If performed appropriately, a short enrichment step is typically sufficient to “produce enough DNA” for subsequent qPCR detection. Moreover, the enrichment process not only increases the concentration of target pathogens in the sample but also revitalizes physiologically stressed or injured microbial cells. Selective enrichment is also crucial for suppressing the naturally occurring background microorganisms, enhancing detection efficiency, and preventing false positive outcomes; however, some of the drawbacks of selective enrichment media include the inhibitory nature of selective agents, which may slow down the growth or even suppress recovery of healthy or stressed target pathogens, ultimately impacting the detection process.

Numerous microbiological culture media with optimized selectivity have been validated and commercialized for short, single-step enrichments for the detection of foodborne pathogens such as Salmonella, Listeria, E. coli, and Campylobacter, across a variety of simplex qPCR assay platforms.

Multiplex qPCR Assays

When a multiplex format is desired, the situation becomes significantly different. Most multiplex qPCR applications are non-commercial and developed in house and open assays, which require standardization and quality assurance for molecular diagnostics. Additionally, multiplex diagnostics are only effective at detecting all target pathogens if they are properly enriched to detectable levels. Overcoming this challenge is difficult since the optimal conditions for detecting one pathogen may not benefit another, and competition among microflora can negatively affect the detection of other pathogens.

Currently, two different approaches are used to enrich food samples prior to detection by multiplex qPCR assays. The first approach involves using non-selective media, such as buffered peptone water (BPW) and universal pre-enrichment broth (UPB), for simultaneous enrichment of multiple foodborne pathogens, including Listeria, Salmonella, and E. coli, in food and environmental samples, followed by detection using multiplex qPCR. However, these broths may recover and enrich target pathogens along with background flora, which can lead to false negative detection results, particularly when complex interfering flora is present in the tested food samples. Therefore, using traditional non-selective enrichment media may not be appropriate for samples with high levels of background microflora, such as raw or unprocessed samples from animal and plant origins.

The second approach employs traditional selective enrichment broths, which help to eliminate interference from background flora in food samples; however, this method necessitates separate enrichment for each type of bacteria being tested. Once each bacterium is individually enriched, small aliquots of the samples are combined into a single diagnostic run. Nevertheless, as multiplex detection platforms evolve to handle several pathogens in a single assay format, it is also important that the enrichment procedures evolve accordingly. Ideally, a single enrichment medium should be used to fully take advantage of multiplexing capabilities.

Desirable for multiplex detection, a multi-pathogen enrichment broth should have the capability to recover sublethally injured cells and selectively enrich all target pathogens from complex background flora in each single or composite food sample. The development of a universal multi-pathogen enrichment medium has become urgent for enabling the simultaneous recovery and concurrent growth of multiple types of bacteria in a single step, making multiplex testing more efficient and cost effective.

Media Development

Developing universal multi-pathogen media requires the careful consideration of several crucial features to guarantee optimal effectiveness and functionality. One such essential characteristic is the ability to simplify the testing process by reducing the required enrichments. Hence, the media should be designed to support multiple bacterial types in a single broth, allowing for greater versatility in testing various food commodities for different target bacteria. This flexibility can streamline the workflow in a food safety testing lab by eliminating the need for multiple culture media preparations and minimizing the risk of errors. Consequently, multi-pathogen media should be formulated with specific nutrients and inhibitors to promote the growth of target bacteria while inhibiting the growth of other bacteria. Such selective enrichment increases the concentration of target bacteria in the sample, improving the sensitivity of subsequent multiplex detection assays, thus ensuring more reliable and accurate outcomes and reducing the risk of false positives or false negatives.

Additionally, multi-pathogen media can enhance the recovery of stressed or sub-lethally injured bacteria that may not grow well in traditional enrichment media, thereby eliminating the possibility of false negative results. The ability to detect stressed or injured pathogenic bacteria is highly desirable in the safety testing of various processed food commodities, such as pasteurized dairy products, deli meats, canned food products, and others. This is because the presence of such bacteria can pose significant risks to consumer health. By identifying these harmful microorganisms, appropriate measures can be taken to prevent their proliferation and minimize the chances of foodborne illness.

Another notable feature of multi-pathogen enrichment media is their ability to support the concurrent growth of different types of bacteria with varying nutritional requirements. Traditional enrichment media are often formulated with specific nutrients to support the growth of a particular type of bacteria, which may not be suitable for other types of bacteria. In contrast, multi-pathogen enrichment media must be formulated with a broad range of nutrients that can simultaneously support the growth of different types of bacteria. Adding specific repair-stimulating and growth-boosting factors, such as siderophores, amino acids, phospholipids, vitamins, and minerals, can help improve recovery and reduce adaptation period for slow-growing bacteria, making multi-pathogen enrichment media versatile and adaptable for various food safety testing applications.

Moreover, multi-pathogen enrichment media can be tailored to specific food matrices, which may vary in their composition and characteristics. Different food types, such as meat, poultry, dairy, fresh produce, and processed foods, may require different enrichment media to facilitate effective recovery of target bacteria due to variations in pH and osmolarity, nutrient content or preservatives, etc. Multi-pathogen enrichment media that contain buffering systems, and osmoprotective and neutralizing molecules can provide optimal conditions for the growth and recovery of specific pathogens in different food matrices. This can result in more accurate and reliable food safety testing outcomes, ultimately enhancing the safety and quality of food products.

Recent investigations into multi-pathogen enrichment media for multiplex foodborne pathogen testing have shown great promise in developing a universal selective enrichment broth. By balancing concentrations of different selective agents and optimizing selectivity levels, it is now possible to achieve simultaneous enrichment of some of the most prevalent foodborne pathogens, such as L. monocytogenes, Salmonella, Shigella, E. coli, and Staphylococcus aureus. While these media formulations have primarily been tested using in-house multiplex qPCR detection platforms, they are not yet commercially available.

As an alternative, in the case of difficult-to-culture foodborne pathogens such as Campylobacter spp., which have unique growth requirements and cannot be enriched in a universal multi-pathogen medium, multiplex testing can be achieved through the combination of enrichment aliquots into a single multiplex run sample.

Multiple Benefits

Using multi-pathogen enrichment media not only provides optimal growth conditions for specific pathogens in different food matrices, but also reduces the cost and storage space required to manage them in a food safety testing lab. This is particularly beneficial for labs with limited resources or space constraints. In addition, multi-pathogen enrichment media can also contribute to sustainability efforts in food safety testing labs. Traditional enrichment media often generate a significant amount of waste, including leftover liquid media and disposable plastic containers. In contrast, using multi-pathogen enrichment media can reduce waste by requiring fewer media formulations and packaging materials. This can promote an environmentally friendly approach to food safety testing, aligning with the increasing focus on sustainability and eco-friendly practices in the food industry.

While multi-pathogen enrichment media offer numerous benefits and features, they require careful validation to ensure compatibility with different multiplex detection platforms. Each multi-pathogen enrichment medium must be validated for its ability to effectively enrich the target bacteria and meet the sensitivity requirements of multiplex assays in detecting these bacteria. This validation process ensures that multi-pathogen enrichment media are reliable and accurate for use in food safety testing, enabling the detection of multiple pathogens in a single assay.

Incorporating universal multi-pathogen media into the enrichment process before testing complements the multiplex detection platform as a comprehensive package technology that evolves to handle multiple pathogens in a rapid, single assay format. The use of the media is a valuable tool in food safety testing, providing numerous benefits and features that can enhance the efficiency, accuracy, and sustainability of the testing process. As food safety remains a top priority in the food industry, the adoption of multi-pathogen enrichment media can significantly contribute to more efficient and reliable multiplex detection methods, ultimately protecting consumer health and well-being.

Dr. Olishevskyy is vice president of research and development FoodChek Laboratories in Sainte-Julie, Quebec, Canada. Reach him at solishevskyy@foodcheksystems.com.

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A group of food scientists from Cornell University in New York have concluded that a standard quality test often used for raw organic milk is not sufficient for differentiating between specific groups of bacteria and should be updated. The research appeared in January in the Journal of Dairy Science (doi: 10.3168/jds.2023-24330).

Nicole Martin, PhD, senior author of the study and assistant research professor in dairy foods microbiology and the associate director of the Milk Quality Improvement Program in the Department of Food Science at the institution, says that the present test, known as the laboratory pasteurization count (LPC), searches for thermoduric bacteria, but doesn’t distinguish whether bacteria form spores or not.

She notes that when dairies deliver organic milk to processors, the milk is sometimes tested for thermoduric bacteria using LPC. Under current standards, if thermoduric bacterial counts are high, the milk can be downgraded or even rejected by the processor. “We saw firsthand the struggle that some dairy farmers had with controlling and troubleshooting the LPC in their raw milk, which selects for thermoduric bacteria, or bacteria that can survive temperatures considerably above their maximum growth temperature,” Dr. Martin tells Food Quality & Safety. “This can lead to loss of premiums and, ultimately, even loss of contracts if the LPC is not brought back into compliance.”

With that in mind, the researchers noted that the criteria for determining milk quality at processing plants is no longer valid and a new way for producers to address milk-production hygiene is necessary.

The researchers went into the study looking to answer a few questions about the LPC that they hear frequently from farmers and other stakeholders, including, “Can milk be frozen prior to LPC testing?” “What are the types of organisms making up the thermoduric population in organic raw milk?” and “Can a rapid identification method used primarily for mastitis organisms be used to identify thermoduric bacteria?”

“So, it’s not necessarily that the LPC is insufficient, but that the LPC alone can only give us so much information, and for farmers who are actively trying to reduce LPC, it may be beneficial to understand the types of bacteria leading to the elevated LPC,” Dr. Martin adds. “This would also for more targeted troubleshooting efforts.”

The research showed that there are two different groups of bacteria making up the thermoduric population in organic raw milk—sporeformers and non-sporeformers—and an individual milk sample with a high LPC may have one or the other, or both, of these types. “Once we know what type of bacteria is driving the elevated LPC, it then allows for more targeted troubleshooting since these groups of bacteria are likely to originate from different sources on the farm,” she says. “We’re giving organic farmers the knowledge they need to make high-quality raw milk and for it to be economically viable; it will make a better dairy product in the end.”

The investigators concluded that, when troubleshooting elevated LPC, it is beneficial to know what the predominant type of thermoduric bacteria are that are contributing to the LPC. “Overall, our research shows that organic raw milk quality is very good, but some producers occasionally deal with high bacteria levels, and often it can take a lot of time and resources to resolve those issues,” Dr. Martin says. “So, when a farmer is dealing with this issue, it is a big problem for them.”

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A new wax coating technology for produce could provide enhanced protection against foodborne pathogens, according to new research publishd in Current Research in Food Science.

The idea was the brainstorm of Mustafa Akbulut, PhD, a professor in the department of chemical engineering at Texas A&M University in College Station, who teamed Luis Cisneros-Zevallos, PhD, a professor in the department of horticultural sciences at the same institution, to design longer-lasting and bacteria-free produce.

“Our collaborative research group combining cutting-edge engineering, food science, and horticulture science is actively engaged in developing new ideas to address issues related to food safety and shelf life,” Dr. Akbulut tells Food Quality & Safety. “In this work, we want to improve the wax that is already applied to many fruits and vegetables in order to enhance their cosmetics and reduce evaporative losses.”

Since a wax coating is already applied to produce, the team looked for a way to make food waxes more functional and beneficial to maximize their potential. “We wanted to create food waxes that have active and passive protection mechanisms against foodborne pathogens and spoilage microorganisms,” Dr. Akbulut says.

The need for this technology has several elements. First, food spoilage is an enormous burden to national economies worldwide. Even increasing the shelf-life of produce by one day can account for huge sums. This is important for sustainability and minimizing waste.

“Additionally, most food industry processes rely on sanitizers in the facility,” Dr. Akbulut says. “Usually, there is no protection after the food commodity leaves the facility. For instance, during transportation and display on grocery shelves, there are ample opportunities for bacterial contamination. At this point, let us imagine multiple people touching and selecting a food commodity from display shelves. Having a strategy to actively protect the food commodity even after it is sanitized and removed from the facility is extremely important.”

The new wax coating technology uses nano-encapsulated essential oils that are evenly distributed in food-grade wax. “The key is to design encapsulation systems that are compatible with the wax materials and can gradually release their contents,” Dr. Akbulut adds. “This method can extend the shelf life of fruits and vegetables by providing a sustained release of bioactive compounds.”

To date, the team have tested the coating against E. coli O157:H7 and S. aureus, demonstrating the product’s effectiveness against common contamination risks.

“It is a conformal coating,” he says. “It can be used for any produce as long as the produce is not very fragile or delicate. It can be commonly applied to many fruits and vegetables, including apples, stone fruits, citrus fruits, cucumbers, bell peppers, eggplants, and tomatoes. These are the starting products. Obviously, commodities more frequent association with foodborne outbreaks can benefit more from this technology.”

He believes that utilizing smarter protective wax coatings can directly translate to performance advantages in the marketplace and is a game changer for the produce industry because it can provide continuous protection of the food commodity even after it leaves the packing/grading facility; growers are already applying wax, so adding functional additives allows them to get additional benefits without major changes to operations; and, the produce will last longer.

The next steps for this technology are to apply it at a production scale to identify and resolve any scaling up issues in translating from lab bench prototypes to commercial packing line implementation. “Our eventual hope is to see this technology broadly implemented across a wide variety of fresh produce,” Dr. Akbulut says. “This would make the produce supply safer while extending shelf life to support sustainability efforts on a global scale by reducing food waste.”

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Tomato juice can kill Salmonella Typhi and other, according to research published in the journal Microbiology Spectrum. Salmonella Typhi is a human-specific pathogen that causes typhoid fever.

“Our main goal in this study was to find out if tomato and tomato juice can kill enteric pathogens, including Salmonella Typhi and, if so, what qualities they have that make them work,” said Jeongmin Song, PhD, associate professor in the department of microbiology and immunology at Cornell University in Ithaca, NY, and principal study investigator, in a press release.

First, the researchers checked to see whether tomato juice really does kill Salmonella Typhi. Once they determined that it did, the team looked at the tomato’s genome to find the antimicrobial peptides that were involved. Antimicrobial peptides are very small proteins that impair the bacterial membrane that keeps them as intact organisms. The researchers found two antimicrobial peptides in the tomato that proved effective against the pathogen.

The investigators conducted more tests on Salmonella Typhi variants that appear in places where the disease is common. They also conducted a digital study to learn more about how the antibacterial peptides kill this and other enteric pathogens.

The researchers concluded that tomato juice is effective in eliminating Salmonella Typhi, its hypervirulent variants, and other bacteria that can harm human digestive and urinary tract health. Specifically, two antimicrobial peptides in the product can eliminate these pathogens by impairing the bacterial membrane, a protective layer that surrounds the pathogen.

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For decades, scientists have sung the praises of lasers and their abilities for observing, detecting, and measuring element in the natural world that are too small for the human eye. The challenge has always been that lasers are expensive and large, making their usage difficult in many situations.

In a study published in the journal Science by Qiushi Guo, PhD, assistant professor at the City University of New York (CUNY) Graduate Center Advanced Science Research Center’s Photonics Initiative and a physics professor at the CUNY Graduate Center, establishes a novel approach for creating high-performance ultrafast lasers on nanophotonic chips, which can be used in multiple sectors, including in the food safety environment.

His work centers on miniaturizing the mode-lock laser, which he describes as “a unique laser that emits a train of ultrashort, coherent light pulses in femtosecond intervals,” equivalent to a quadrillionth of a second. His research leverages an emerging material platform known as thin-film lithium niobate (TFLN), which allows for efficient shaping and precise control of laser pulses by applying an external radio frequency electrical signal.

Thanks to its compact size, it could mean that these ultrafast mode-locked lasers could one day allow for cell phones to diagnose eye diseases or environments to be analyzed for E. coli and other pathogens.

“Revealing the intricacies of unknown substances and understanding their chemical composition necessitates a powerful tool: infrared absorption spectroscopy,” Dr. Guo tells Food Quality & Safety. “This technique has the capacity to sensitively detect highly characteristic rotational or vibrational transition bands exhibited by a diverse range of molecules and functional groups, i.e. the ‘fingerprints’ of various chemicals.”

He says that when integrated with a nonlinear optical spectral broadening element and a photodetector, the chip-scale mode-locked laser can be used to create an ultracompact infrared absorption spectroscopy spectrometer which can be carried by people. “By directing or the laser’s output onto the food under examination and analyzing the reflected light spectrum, we can rapidly decipher and reconstruct the chemical composition present in the food,” Dr. Guo says. “Also, compared to other chip-scale spectrometer techniques, our laser can generate very bright signal light, which increases the accuracy of the analysis.” This approach allows people to swiftly identify potential hazards, providing a valuable tool for ensuring food safety and protecting public health.

Traditionally, food safety inspections have been confined to laboratories, using sophisticated equipment inaccessible in people’s daily lives. Consequently, obtaining a clear understanding of food safety before eating is almost impossible. This new technology transforms this paradigm by miniaturizing the spectrometer to a size comparable to phone cameras. “Now, food safety inspections can be effortlessly conducted at home or in restaurants with a simple click on our phones,” Dr. Guo says. “This innovation significantly diminishes the risk of foodborne illnesses, making the [inspection] process more accessible and timely.”

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The Centers for Disease Control and Prevention (CDC) has uncovered a new strain of E. coli that has been responsible for multiple outbreaks of foodborne illness over recent years, including those related to romaine lettuce and other leafy greens.

The REPEXH02 strain is believed to have first come to light at the end of 2015, with the agency noting that it was responsible for dozens of hospitalizations and many cases of hemolytic uremic syndrome (HUS), a serious issue that can often impede blood clotting in infected people and cause kidney failure.

A study by CDC researchers utilized whole genome sequencing to examine the DNA of a strain and track the bacteria that cause foodborne illness, which allowed them to determine whether outbreaks were caused by the same strain, and the link involved with others. The new strain consists of two clades with different geographic distributions, one of which has notable genomic features.  

E. coli O157:H7 is estimated to cause 63,000 domestically acquired foodborne illnesses and 20 deaths in the United States each year, according to the CDC. The agency found that 58% of recent E. coli-related illnesses were attributed to vegetable row crops, with the majority coming from leafy greens. In 2019, a large outbreak related to romaine lettuce from California’s Salinas Valley caused 167 cases and hospitalized 85 people from 27 states. In 2020, 40 infections occurred in 19 states, 20 people were hospitalized and four developed HUS. No further outbreaks from the strain have been associated with the strain.

The newly identified strain has a toxin type associated with more severe disease in those infected, according to the CDC. Still, additional study is needed to understand factors that contribute to the bacteria’s emergence and persistence in specific environments, the authors wrote.

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Infant formula safety checks can be improved with stratified sampling, according to a new study from the Department of Food Science and Human Nutrition at the University of Illinois in Urbana-Champaign.

“Our lab had a prior project simulating bulk product sampling to improve food safety sampling plans for detecting aflatoxin in corn in bins and bacterial pathogens on leafy greens produce in fields,” Minho Kim, a PhD student and the study’s lead author, tells Food Quality & Safety. “We then wanted to adapt that simulation to bulk products, like powdered products.”

The authors found there was data available for Cronobacter in powdered infant formula produced in Europe in the 2010s, and chose to work on that problem. The subsequent outbreak and recall in the U.S. then provided additional relevance to the work.

Stratified random sampling is a pattern where you first pick an interval of time, e.g., every 10 minutes of production, and then take a sample randomly during each of those production intervals. “Sampling and testing play an important role in the HACCP plan by monitoring if the system is operating properly,” Kim says. “Thus, sampling plans should have enough power to detect pathogens of concern. There is an existing sampling guideline for testing Cronobacter provided by CODEX Alimentarius for powdered infant formula (30 samples of 10g); however, the sampling plan might not always work the same under different contamination profiles or production scales.”

Therefore, the researchers developed a web application for the sampling simulation tool that stakeholders can use to explore the power of sampling plans in different production lot and contamination profiles.

“Our major findings include that existing sampling guideline for detecting Cronobacter spp. in powdered infant formula products will be powerful enough to detect the contamination observed in a previously studied recalled batch from Europe, but not the non-recalled batch profile,” Kim adds. “By simulating different sampling plans with the recalled and non-recalled profiles, we were able to see the trend that taking more samples and adopting the sampling pattern with stratification help increase power to detect the contamination.”

A future discussion, he says, will be to investigate opportunities to reduce this residual risk in the powdered infant formula products. “A few babies getting sick from each outbreak cluster may represent the chance of this residual risk being problematic,” Kim adds. “One possible strategy is to use more active labeling on incorporating hot water reconstitution, like other countries [do]. A risk assessment done by WHO/FAO in 2006 showed that using 70°C water for reconstitution can significantly reduce the risk by inactivating Cronobacter sakazakii without damaging essential nutrients for babies. However, we heard about concerns from doctors in France where babies were coming to the hospital with burned throats. We hope more discussions about using hot water reconstitution between experts can lead to reduced Cronobacter illnesses.”

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An ad hoc committee under the auspices of the National Academies of Sciences, Engineering, and Medicine (NASEM) will examine challenges in the supply, market competition, and regulation of infant formula in the U.S. The project is sponsored by FDA.

The study will explore the current state of the country’s infant formula market, including the diversity of manufacturers; the types of formulas they produce (e.g., non-specialty or specialty, powdered, or liquid); manufacturing facilities, production, and production capacity; the amounts of infant formula produced domestically and the amounts imported; and other characteristics.

The study will also examine how these characteristics compare with those of the market prior to the COVID-19 pandemic, and just prior to the Abbott recall in February 2022. The study will consider a range of conditions and systems that may be influencing competition in market. Additionally, the National Academies will examine the differences in the nutritional content, labeling, and other regulatory requirements between infant formula sold in the United States and formula sold in foreign markets, such as in the European Union.

As part of the Food and Drug Omnibus Reform Act of 2022, Congress directed FDA to develop an Immediate National Strategy to Increase the Resiliency of the U.S. Infant Formula Market, which was released in March 2023; to engage with NASEM on a deeper study of challenges in the U.S. supply, market competition, and regulation of infant formula; and then for FDA to use the information gained through the NASEM study to develop a long-term national strategy.

NASEM will submit its findings to both Congress and FDA.

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A study conducted at the University of Connecticut in Storrs and recently published in Food Microbiology found that protective bacterial cultures offer a promising mechanism for combating antibiotic-resistant Salmonella in food.

Dennis D’Amico, PhD, associate professor of dairy foods in the University of Connecticut’s College of Agriculture, Health and Natural Resources, led the study as part of his ongoing work involving the use of protective bacterial cultures to prevent illness from foodborne pathogens. He has previously studied the use of bacterial cultures to control the growth of pathogens in food products and to impede their ability to cause sickness.

Dr. D’Amico says that some microbial strains, including many strains of Salmonella, have developed resistance to many of the antibiotics used in human medicine, so the goal of this study was to find an effective way to target those pathogens without using antibiotics. The study authors considered the ability of a protective culture called Hafnia alvei B16 to prevent infection by two Salmonella serovars.

Previously, Dr. D’Amico’s lab had identified Hafnia alvei B16 as effective in inhibiting the growth of both E. coli and Salmonella in milk, and it also successfully stopped the growth of Staphylococcus aureus, preventing it from producing toxin levels sufficient to cause disease in humans.

“Protective cultures like the commercial products we have tested in the lab work against other bacteria in various ways, typically through competitive exclusion and the production of antimicrobial metabolites such as organic acids and bacteriocins,” Dr. D’Amico tells Food Quality & Safety. “They are typically added to products to inactivate or suppress the growth of unwanted microbes. We have shown this [result] with several cultures against several pathogens in food.”

Once ingested, certain pathogens must continue to grow in the gut until the population is large enough to cause disease. Other microbes such as Staph aureus produce a toxin that can cause severe disease if they are allowed to grow unchecked.

The report explains that these cultures can also reduce the virulence of certain pathogens when present together in a food, much like other cultures labeled as probiotics. These cultures can improve food safety by controlling pathogen growth and survival in a food product, thereby attenuating their virulence in food, and/or providing protection against colonization in the host.

“In this case, we see these effects even against antibiotic resistant strains,” Dr. D’Amico says. “The most important takeaway is that these cultures, which are typically used only to control the outgrowth of pathogens in food, have additional functions to provide a multi-pronged approach to improving food safety and public health.”

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FDA has announced that it has worked with the Environmental Protection Agency (EPA) to update the protocol for the development and registration of treatments for pre-harvest agricultural water to remove Listeria monocytogenes from the organism test panel.

FDA says that this change is being made because pilot studies have found that sanitizer treatments that will likely be effective for E. coli and Salmonella may be different from those that are most effective for L. monocytogenes. This is likely due to the physical characteristics of E. coli and Salmonella being distinctly different from those of L. monocytogenes. In light of recent outbreaks of Shiga toxin-producing E. coli (STEC) and Salmonella linked to produce, FDA and EPA agreed and decided to move forward with removing this pathogen from the panel.

“We expect that doing so will facilitate the registration of antimicrobial treatments against STECs (and other E. coli) and Salmonella in pre-harvest agricultural water, the availability of which will be a significant resource for farms to protect their crops against these pathogens,” FDA said in a statement. “While we are removing L. monocytogenes from the protocol at this time, companies may opt to continue testing against L. monocytogenes for inclusion in their registration with EPA.

Recent outbreaks of foodborne illness associated with the consumption of romaine lettuce and other leafy greens have highlighted the need for a viable option for treating agricultural water against foodborne pathogens.

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