There’s no need to send a sympathy card to Salmonella. Yes, this proud bug dropped into second place on CDC’s list of organisms responsible for foodborne illness in the U.S. in 2016, with 8,172 cases reported on CDC’s Foodborne Diseases Active Surveillance Network (FoodNet), compared to 8,547 cases for Campylobacter. But Salmonella took the lead among all foodborne bacterial pathogens for causing most hospitalizations, 2,255, and deaths, 40, as reported in FoodNet’s April 21, 2017 issue of the Morbidity and Mortality Weekly Report.
CDC estimates this relentless gram negative rod causes about 1.2 million illnesses in the U.S. annually, not to mention 23,000 hospitalizations and 450 deaths. Food is the source for about one million of these illnesses.
Salmonellosis in humans is generally contracted through the consumption of contaminated food
of animal origin, mainly eggs, meat, poultry, and milk, although other foods, including fruits and vegetables, have been implicated in its transmission.
Specifically, foods that are most likely to contain Salmonella include raw or undercooked eggs, raw milk, contaminated water, and raw or undercooked meats. Eating unwashed vegetables or fruits, including seeded vegetables and sprouts, increases the risk of Salmonella infection. In recent years, contamination with Salmonella has been found in a variety of tree nuts, including almonds, cashews, pistachios, pine nuts, Brazil nuts, macadamia nuts, and walnuts.
According to the December 2017 report by the Interagency Food Safety Analytics Collaboration (IFSAC) that addresses foodborne illness source attribution estimates for 2013, 75.4 percent of Salmonella illnesses were attributed to seven food categories: seeded vegetables (16 percent), eggs (11.5 percent), chicken (10.4 percent), other produce, such as nuts (9.8 percent), pork (9.3 percent), beef (9.1 percent), and fruits (8.9 percent).
The IFSAC is a tri-agency group created by the CDC, FDA, and the USDA’s Food Safety and Inspection Service.
Salmonella challenges abound, but fortunately, much tireless work is in progress to minimize the negative effects of this organism throughout the food chain.
(In the plus column for Salmonella, the organism is demonstrating remarkable capabilities for treating brain cancer, but that’s another story. Bugs as drugs definitely hold promise, research shows.)
Faster Salmonella Test
A new diagnostic procedure has been developed that provides accurate, rapid testing for Salmonella, including serotype Dublin, an emerging food animal and food safety concern.
Salmonella Dublin can be difficult or slow to grow in culture, typically making detection challenging, according to Laura Goodman, PhD, an assistant research professor in the Department of Population Medicine and Diagnostic Sciences (PMDS) at Cornell University, Ithaca, N.Y., and lead author of the study that resulted in this new rapid test.
“Tests for Salmonella environmental screening used to take days, now they take 24 hours,” Dr. Goodman points out. “The new method can also detect one hundredfold fewer Salmonella Dublin bacteria.”
Salmonella Dublin is host adapted in cattle, meaning infected animals can become permanent or long-term carriers, putting herd mates, especially susceptible calves, at risk, explains Belinda Thompson, DVM, a PMDS assistant clinical professor and senior author on the study. “This serotype can infect people who may be exposed by contact with infected animals, by drinking raw milk, or by consuming other contaminated food products,” she relates. “In humans, Salmonella Dublin has higher hospitalization and fatality rates than other Salmonella types; it causes systemic infection of body tissues, similar to typhoid.”
Similarly, in cattle, serotype Dublin is associated with invasive disease, multi-drug resistance, and opportunities for infection following survival in the environment, Dr. Thompson mentions.
“Salmonella enterica subspecies enterica serotype Dublin (S. enterica Dublin) emerged for the first time in New York, Pennsylvania, and Ohio in 1988,” she notes. “Since that time this serotype has spread throughout the veal and dairy beef raising operations in the region.”
To tackle Salmonella diagnosis, Dr. Goodman and her team developed a workflow for testing veterinary matrices, including enteric and cloacal tissues (mostly from cows, but also from alpaca, chicken, clouded leopard, deer, duck, gazelle, goat, goose, hooded crane, horse, rabbit, raccoon, and turtle species), feces (from cows, dogs, and horses), and feed, plus environmental samples, by using real-time polymerase chain reaction after selective enrichment in Rappaport-Vassiliadis soya medium.
The study was funded by and performed in collaboration with the FDA’s Veterinary Laboratory Investigation and Response Network.
Dr. Goodman says that the new method to detect Salmonella is now available as an environmental testing program for animal facilities through Cornell’s Animal Health Diagnostic Center (AHDC). “The test covers all S. enterica subspecies and serotypes and offers next-day results,” she relates.
Stakeholders throughout the country can access the testing on a fee for service basis by shipping samples to the AHDC. “Instructions are available on our website,” Dr. Goodman says.
“Salmonella biosurveillance in veterinary facilities and on farms is critical because animals can shed the bacteria without showing clinical disease signs,” Dr. Thompson emphasizes. “Thanks to the 24-hour turnaround time with the new test, infected animals in a hospital or clinic setting or on a farm can be quarantined, and contaminated environments can be identified to ensure other animals are not being exposed to Salmonella Dublin.”
The AHDC environmental test for Salmonella is applicable to poultry farms, Dr. Goodman notes, although the new rapid method is not a National Poultry Improvement Plan (NPIP) test. “We would encourage this testing in addition to NPIP testing if poultry producers wanted to monitor for any Salmonella, not specifically Enteritidis,” she advises.
Dr. Goodman says that, while the AHDC Salmonella testing protocol is potentially applicable to food manufacturing plants and food besides raw milk, and could be adopted by other labs, the AHDC does not test human food products.
Dry Surrogate Organisms
Based in historic Dijon, France, birthplace of the famous mustard and just 30 miles from the birthplace of Louis Pasteur, a company called Novolyze is making an international name for itself that would surely make the “Father of Microbiology” proud.
Novolyze is a developer and manufacturer of dry, ready-to-use surrogate microorganisms that mimic the behavior of foodborne pathogens, and thus make it possible for food companies to perform in-plant preventive control validations.
While Novolyze has developed a full range of surrogate microorganisms qualified for different kinds of food products, target pathogens, and kill steps, the firm’s signature product is a patented dry Salmonella surrogate marketed under the trade name SurroNov.
“Our surrogate products are non-pathogenic, so food manufacturers can validate their processes right in their own production lines,” says Karim-Frank Khinouche, the firm’s founder and CEO. “SurroNov surrogates validate such products as spices, nuts, cocoa, pet food, powders, cereals, pasta, flour, cookie dough, and baked goods; and they can be used in extruder, steam pasteurizer, oven, and dryer applications.”
Khinouche explains that SurroNov surrogates are formulated with food-grade ingredients to stabilize them, while ensuring initial inoculation levels and their thermal behaviors remain the same. All SurroNov surrogates are Biosafety Level 1 microorganisms.
“SurroNov’s high-volume production capability enables a manufacturer to inoculate multiple tons of product, which is important, for example, if an extruder is producing 300 pounds of product per minute,” Khinouche notes. “Another benefit is being able to run validation/challenge studies in-house, rather than incurring the expense of third party laboratories.”
The patented SurroNov surrogates are available in unit pouches ranging from 25 grams to 1 kilogram, Khinouche relates. They can also be acquired pre-inoculated with a food ingredient, packed in bulk pouches, or in thermally-resistant bags or thermal balls for a faster and easier in-plant use.
Khinouche says the dry nature of SurroNov reduces the impact on the physical-chemical properties of the food matrix. Additional benefits include that these dry surrogates can be directly incorporated into a food matrix without an enrichment step; there is a guaranteed inoculation concentration and more favorable heat resistance to the target pathogen compared with liquid surrogates; and there’s also the ability to reach higher inoculation levels than methods using liquid surrogates, up to 10-log colony forming units per gram.
In July 2017, Novolyze won the prestigious International Association for Food Protection (IAFP) Food Safety Innovation Award for its development of this first-of-its-kind Salmonella surrogate.
Khinouche is quick to emphasize that low moisture foods producers didn’t have a safe, user friendly, cost effective method to validate their processes until the game changing Novolyze dry surrogates were introduced commercially in 2016.
“That is why we won the IAFP award,” he boasts. “We believe in-plant process use of SurroNov surrogates is one of the easiest, safest, and fastest ways to validate a kill step and ensure compliance with the FSMA Preventive Controls for Human Food.”
Maximizing the microbiological safety of processed food with surrogate trials is definitely a hot topic for food processors, Khinouche adds. “We’re seeing a lot of food companies getting a jump on validation procedures even before acquiring new processing technology,” he points out. “A number of our clients are using our surrogate bacterial preparations at the pilot stage, sometimes right at their equipment vendor’s facilities. The major benefit here is the possibility to test the equipment and its ability to maintain the desired process controls before deciding to make major capital purchases. By taking advantage of our surrogate technology in this way, we believe food processors are better able to insure the soundness of investments that sometimes involve hundreds of thousands of dollars.”
Using surrogate bacteria at the pilot stage allows food processors the opportunity to obtain a more precise vision of process efficacy, Khinouche continues. “For some companies, our technology opens the way for significant process optimizations,” he elaborates. “In that regard, the major benefits are a better preservation of the organoleptic and nutritional quality of foods; increased throughput productivity of up to 40 percent or even more; and improvement of sustainability score, such as up to 35 percent less chemicals used for pathogen inactivation.”
On Oct. 31, 2017, Novolyze, which also maintains an affiliate in Cambridge, Mass., was chosen to participate in the second cohort of TERRA, the Food + Ag Tech Accelerator, as one of 18 food and agriculture startups that are deemed most disruptive and progressive. Additionally, in November 2017, Novolyze was awarded grant funds from the French government to develop validation innovations for pre-cut, fresh, and frozen fruits and vegetables.
La Tortilla Factory, Santa Rosa, Calif., manufacturer of 1.2 million tortillas per day, first used SurroNov dry Salmonella surrogate at its 75,000-square-foot plant in early September 2017. “We needed documentation of our thermal processing procedures in order to comply with Food Safety Modernization Act regulations,” says Nathan Wilson, the company’s quality assurance manager. “Since our products typically have water activity of .9 to .99, they are at high risk for bacterial spoilage. So we needed solid data and validation.”
Since SuroNov is a dry product, the La Tortilla Factory team anticipated that the bacterial surrogate would not interfere with the products’ water activity.
“We ran validation tests two times in one week, using 45 grams of SuroNov each to inoculate tortilla dough samples on numerous production lines and in several ovens,” Wilson relates. “We tested samples after the heated press step that precedes the oven, and then after cooling of the finished product coming from the oven. We did due diligence with inoculated samples and controls.”
Wilson reports that, at the end of this testing, there were no positive results for Salmonella. “It was a very good validation and we got our data buttoned up,” he relates. “SuroNov gave us a higher log reduction, as typical labs will inoculate at 5 log, whereas Novolyze offers 10 log. And at the end, the total log of inoculation was at 9.2 from the 10 expected. The water activity of the dough samples was at 0.96.”
Wilson adds that a subsequent running of the validation protocol with SuroNov a couple more times over a lower oven temperature than would normally be used afforded a thermal mapping of the company’s ovens for their research and development team.