Raw is risky: Salmonella growth on sprouts and microgreens

Microgreens, like sprouts, are relatively fast-growing products and are generally consumed raw. Moreover, as observed for sprouts, microbial contamination from preharvest sources may also be present in the production of microgreens.

In this study, two Salmonella enterica serovars (Hartford and Cubana), applied at multiple inoculation levels, were evaluated for survival and growth on alfalfa sprouts and Swiss chard microgreens by using the most-probable-number (MPN) method. Various abiotic factors were also examined for their effects on Salmonella survival and growth on sprouts and microgreens. Community-level physiological profiles (CLPPs) of sprout/microgreen rhizospheres with different levels of S. enterica inoculation at different growth stages were characterized by use of Biolog EcoPlates. In the seed contamination group, the ability of S. enterica to grow on sprouting alfalfa seeds was affected by both seed storage time and inoculation level but not by serovar. However, the growth of S. enterica on Swiss chard microgreens was affected by serovar and inoculation level. Seed storage time had little effect on the average level of Salmonella populations in microgreens. In the irrigation water contamination group, the growth of Salmonella on both alfalfa sprouts and microgreens was largely affected by inoculation level. Surprisingly, the growth medium was found to play an important role in Salmonella survival and growth on microgreens. CLPP analysis showed significant changes in the microbial community metabolic diversity during sprouting for alfalfa sprouts, but few temporal changes were seen with microgreens. The data suggest that the change in rhizosphere bacterial functional diversity was dependent on the host but independent of Salmonella contamination.

Sprouts and microgreens are considered “functional foods,” i.e., foods containing health-promoting or disease-preventing properties in addition to normal nutritional values. However, the microbial risk associated with microgreens has not been well studied. This study evaluated Salmonella survival and growth on microgreens compared to those on sprouts, as well as other abiotic factors that could affect Salmonella survival and growth on microgreens. This work provides baseline data for risk assessment of microbial contamination of sprouts and microgreens. Understanding the risks of Salmonella contamination and its effects on rhizosphere microbial communities enables a better understanding of host-pathogen dynamics in sprouts and microgreens. The data also contribute to innovative preventive control strategies for Salmonella contamination of sprouts and microgreens.

Plant-microbe and abiotic factors influencing salmonella survival and growth on alfalfa sprouts and Swiss chard microgreens

16 February 2018

Applied and Environmental Microbiology, vol 84 no 9

Elizabeth ReedaChristina M. Ferreiraa, Rebecca BellaEric W. Browna and Jie Zhenga

doi:10.1128/AEM.02814-17

http://aem.asm.org/content/84/9/e02814-17.abstract?etoc

105 sickened, 1 death linked to Salmonella Newport outbreak originating in beef from dairy cattle, 2016-17

Contaminated ground beef was the likely source of a protracted outbreak of 106 Salmonella Newport infections, 42 hospitalizations, and one death in 21 states during October 2016–July 2017. While no direct link was found, whole genome sequencing suggests dairy cows were the ultimate outbreak source.

Foodborne outbreak investigations could be enhanced by improvements in the traceability of cows from their originating farms or sale barns, through slaughter and processing establishments, to ground beef sold to consumers.

In January 2017, the U.S. Centers for Disease Control (CDC) identified a cluster of Salmonella enterica serotype Newport infections with isolates sharing an indistinguishable pulsed-field gel electrophoresis (PFGE) pattern, JJPX01.0010 (pattern 10), through PulseNet, the national molecular subtyping network for foodborne disease surveillance. This report summarizes the investigation by CDC, state and local health and agriculture departments, and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) and discusses the possible role of dairy cows as a reservoir for strains of Salmonella that persistently cause human illness. This investigation combined epidemiologic and whole genome sequencing (WGS) data to link the outbreak to contaminated ground beef; dairy cows were hypothesized to be the ultimate source of Salmonella contamination.

A case was defined as infection with Salmonella Newport with PFGE pattern 10 closely related to the outbreak strain by WGS, with bacterial isolation during October 1, 2016, through July 31, 2017. A total of 106 cases were identified in 21 states (Figure 1). Most illnesses ([72%]) were reported from southwestern states, including Arizona (30), California (25), New Mexico (14), and Texas (seven). Illness onset dates ranged from October 4, 2016, through July 19, 2017. Patients ranged in age from <1–88 years (median = 44 years), and 53 (50%) were female. Among 88 (83%) patients with known outcomes, 42 (48%) were hospitalized, and one died.

Initial interviews identified consumption of ground beef as a common exposure among patients. A focused questionnaire was developed to collect detailed information on ground beef exposure and to obtain shopper card information and receipts. Among 65 interviewed patients, 52 (80%) reported eating ground beef at home in the week before illness began. This percentage was significantly higher than the 2006–2007 FoodNet Population Survey, in which 40% of healthy persons reported eating ground beef at home in the week before they were interviewed (p<0.001) (1). Among the 52 patients who ate ground beef at home, 31 (60%) reported that they bought it or maybe bought it from multiple locations of two national grocery chains, and 21 (40%) reported that they bought ground beef from locations of 15 other grocery chains. Specific ground beef information was available for 35 patients. Among these, 15 (43%) purchased ground beef as chubs (rolls) of varying sizes (range = 2–10 lbs), 18 purchased it on a tray wrapped in plastic, and two purchased preformed hamburger patties. Twenty-nine patients reported that they bought fresh ground beef, four bought frozen ground beef, and four did not recall whether it was fresh or frozen when purchased. When asked about ground beef preparation, 12 (36%) of 33 patients reported that they definitely or possibly undercooked it.

Traceback Investigation

USDA-FSIS conducted traceback on ground beef purchased within 3 months of illness onset for 11 patients who provided shopper card records or receipts. Approximately 20 ground beef suppliers belonging to at least 10 corporations were identified; 10 of the 11 records traced back to five company A slaughter/processing establishments, seven of 11 traced back to five company B slaughter/processing establishments, and four of 11 traced back to two company C slaughter/processing establishments.

Product and Animal Testing

Opened, leftover samples of ground beef from three patients’ homes were collected for testing. All were purchased from one of two national grocery chains that had been identified by a majority of patients. One sample, collected from ground beef removed from its original packaging, yielded the outbreak strain. The other two samples did not yield Salmonella.

The outbreak strain was also isolated from four New Mexico dairy cattle. One was collected from a spontaneously aborted fetus in July 2016, and one was isolated from feces from a young calf in November 2016. The third isolate was identified by searching the USDA Animal and Plant Health Inspection Service National Veterinary Services Laboratory (USDA-APHIS NVSL) database for Salmonella Newport isolates collected from cattle in Arizona, California, Texas, New Mexico, and Wisconsin during January 2016–March 2017. Eighteen Salmonella Newport isolates were identified, including 13 from Texas, three from New Mexico, and two from Wisconsin. The only Salmonella Newport pattern 10 isolate identified was from a fecal sample from a New Mexico dairy cow collected during November 2016. The fourth isolate was from a USDA-FSIS routine cattle fecal sample collected at a Texas slaughter establishment in December 2016; USDA-FSIS determined the sample was from a dairy cow and identified the New Mexico farm of origin. Because of confidentiality practices, officials were not able to identify the farm or farms of origin for the dairy cows associated with the other three samples or whether the four dairy cows were associated with a single farm. None of the 11 patients with information for traceback ate ground beef produced at the Texas slaughter establishment.

Whole genome high-quality single nucleotide polymorphism (SNP) analysis* showed that 106 clinical isolates were closely related to each other genetically, to the four dairy cattle isolates, and to the leftover ground beef isolate (range = 0–12 SNP differences), suggesting that the Salmonella bacteria found in patients, ground beef, and dairy cattle all shared a common source. Thirty-nine additional clinical isolates with PFGE pattern 10 were determined to not be closely related and were excluded from the outbreak. No antibiotic resistance was detected among three clinical isolates tested by CDC’s National Antimicrobial Resistance Monitoring Laboratory.

Because the USDA-FSIS traceback investigation did not converge on a common production lot of ground beef or a single slaughter/processing establishment, and no ground beef in the original packaging yielded the outbreak strain, a recall of specific product was not requested. A public warning was not issued to consumers because specific, actionable information was not available (e.g., a specific brand or type of ground beef). Officials in New Mexico visited the dairy farm that was the source of the cow at the Texas establishment and noted no concerns about conditions or practices. However, this visit occurred late in the investigation, and conditions at the time of the visit might not have represented those present immediately before and during the outbreak. No samples from the environment or cows were collected during this visit.

Epidemiologic and laboratory evidence indicated that contaminated ground beef was the likely source of this protracted outbreak of Salmonella Newport infections. A significantly higher percentage of patients than expected ate ground beef at home, and a patient’s leftover ground beef yielded the outbreak strain. Dairy cows colonized or infected with the outbreak strain before slaughter are hypothesized to be the ultimate outbreak source. Most U.S. ground beef is produced from beef cattle; however, 18% is produced from dairy cows (2). Dairy cows are sold for beef production through sale barns or directly to slaughter establishments as they age or if their milk production is insufficient (2). Previous studies have demonstrated long-term persistence of Salmonella Newport in dairy herds (3,4), and a 1987 Salmonella Newport outbreak was linked to contaminated ground beef from slaughtered dairy cows (5). In the current outbreak, as has been observed in previous outbreaks, ground beef purchases traced back to numerous lots and slaughter/processing establishments (6). One possible explanation is that dairy cows carrying a high Salmonella load that overwhelmed antimicrobial interventions could have gone to multiple slaughter/processing establishments (7), resulting in contamination of multiple brands and lots of ground beef. This might explain the reason for failure to identify a single, specific source of contaminated ground beef.

This investigation identified the outbreak strain only in samples from dairy cattle from New Mexico. All four isolates from dairy cattle samples were closely related genetically by WGS to isolates from patients, providing further evidence of a connection between dairy cattle in New Mexico and the outbreak. The disproportionate geographic distribution of cases in the U.S. Southwest, including New Mexico, also suggests a possible regional outbreak source. Although limited in scope, the query of the USDA-APHIS NVSL data identified the outbreak strain only from one New Mexico dairy cow (isolate 3), and the sample collection date was consistent with the timing of illnesses in this outbreak. The overall prevalence and geographic distribution of the outbreak strain in cattle is not known, and it is possible that cattle in states other than New Mexico might have been infected or colonized with the outbreak strain.

This was a complex and challenging investigation for several reasons. First, the PFGE pattern in the outbreak was not uncommon in PulseNet, making it difficult to distinguish outbreak cases from sporadic illnesses associated with the same Salmonella Newport pattern. WGS analysis provided more discriminatory power to refine the outbreak case definition and excluded 39 cases of illness from the outbreak. However, sequencing is not currently performed in real time for Salmonella, thereby slowing the process of determining which cases were likely outbreak-associated. In addition, a direct pathway linking outbreak cases to dairy cows infected with the outbreak strain of Salmonella Newport could not be established. This is because product traceback did not converge on a single contaminated lot of ground beef, and investigators were unable to ascertain a link between the beef slaughter/processing establishments identified during traceback and the farms with dairy cows that yielded the outbreak strain. Tracing back ground beef purchased by patients to slaughter/processing establishments requires documentation such as receipts or shopper card records, and only 10% of patients had this information available. For this outbreak, tracing back cows at slaughter/processing establishments to the farm from which they originated was problematic because cows were not systematically tracked from farm to slaughter/processing establishments.

Four points along the “farm to fork” continuum provide opportunities to prevent consumers from becoming ill from contaminated ground beef. First, farms can implement good management practices for cattle health, including vaccination, biosecurity (e.g., controlling movement of persons and animals on farms, keeping a closed herd [so that no animals on the farm are purchased, loaned to other farms, or have contact with other animals], planning introduction of new animals and quarantining them, and performing microbiologic testing of animals), and cleaning and disinfection measures to decrease Salmonella burden in animals and the environments in which they reside, reducing the likelihood that Salmonella will enter beef slaughter/processing establishments (8). Second, slaughter/processing establishments are required to maintain Hazard Analysis and Critical Control Points systems to reduce Salmonella contamination as well as slaughter and sanitary dressing procedures to prevent carcass contamination (9). Third, although Salmonella is not considered an adulterant in not-ready-to eat (NRTE) meat products, USDA-FSIS likely will consider the product to be adulterated when NRTE meat products are associated with an outbreak (9). Finally, consumers are advised to cook ground beef to 160°F (71°C) as measured by a food thermometer to destroy any bacteria that might be present. Consumers are also advised to wash hands, utensils, and surfaces often; separate and not cross-contaminate foods; and refrigerate foods promptly and properly.

This investigation emphasizes the utility of WGS during outbreak investigations and identifies the need for improvements in traceability from the consumer to the farm. It also highlights the importance of continued evaluation of farm practices to help reduce persistent Salmonella contamination on farms, contamination of ground beef, and ultimately human illness.

Protracted outbreak of Salmonella Newport infections linked to ground beef: Possible role of Dairy Cows-21 states, 2016-2017

CDC

https://www.cdc.gov/mmwr/volumes/67/wr/mm6715a2.htm

Kis Robertson Hale, Food Safety and Inspection Service, U.S. Department of Agriculture; territorial, state, city, and county health departments and laboratories; Danya Alvarez, John Crandall, Hillary Berman-Watson, California Department of Public Health Microbial Diseases Laboratory.

 

What will I do with those tossed salads and scrambled eggs? Ditch them

Amy and I agree on this: If we need to fall asleep, put on an episode of Frasier.

Five minutes later we’re in la-la land.

Inspectors with the U.S. Food and Drug Administration say they found dozens of rodents and poor worker hygiene at a North Carolina chicken farm operated by an Indiana egg producer that last week recalled more than 200 million eggs.

Vic Ryckaert and Holly Hays of the Indy Star report that according to a FDA report, inspectors spent March 26 to April 11 at the Rose Acre Farms egg operation in Pantego, North Carolina, and found “unacceptable rodent activity” and dirty equipment. They also noted employees touching dirty floors, equipment and their bodies without washing their hands.

The unsafe conditions allow “for the harborage, proliferation and spread of filth and pathogens,” inspectors said.

In an emailed statement, Seymour-based Rose Acre Farms said the inspection report “is based on raw observations and in some cases lack proper context.”

“It’s unfair to be judged on the farm’s operation without proper perspective or a chance to formally respond to an incomplete representation of a massive facility that houses more than three million hens,” the company said. 

Context this.

The company said it will make public its response to the inspection, which is due on April 26.

“Until then, we would urge everyone to wait until all the facts are presented before rushing to judgment,” the company said.

The FDA said at least 23 illnesses have been reported. The eggs were distributed to consumers in Colorado, Florida, New Jersey, New York, North Carolina, Pennsylvania, South Carolina, Virginia and West Virginia.

FDA spokesman Peter Cassell declined to comment specifically about the Rose Acre Farms inspections but said the facility must correct the issues before the next inspection or face repercussions. Consequences could include product seizures or, in a more serious step, shutting down the facility. 

Cassell encouraged shoppers not to assume that they are not exposed to the recall because they are not geographically near the states where cases have been reported.

“Consumers should look for the brands and the lot numbers we provided,” he said. “We want to make sure that people are getting the right information.”

The recall involved eggs sold under the brand names Country Daybreak, Crystal Farms, Coburn Farms, Sunshine Farms, Glenview and Great Value. Also included were eggs sold at Walmart and Food Lion stores.

The cartons were stamped with plant number P-1065 and the Julian date range of 011 through 102.

The company’s Hyde County Egg facility in North Carolina produces 2.3 million eggs a day.

Inspectors found “insanitary conditions and poor employee practices” throughout the farm, according to the FDA report.

The inspectors’ observations in the report included:

Dozens of live and dead rodents, including baby mice, in chicken houses and manure pits.

Employees skipping steps in the cleaning process by wiping off detergent before allowing it to soak in the eggs.

Condensation dripping onto crack detectors, egg graders and other production equipment.

Water pooling on floors and forklift pathways.

Grimy, dirty floors, pallets and equipment. 

Farm workers touching dirty equipment and trash cans as well as their face, hair and “intergluteal cleft” before touching eggs or handling equipment that touches eggs without washing hands or changing gloves.

Fancy food ain’t safe food: Possible Salmonella infections at popular Brisbane eatery

Holly Hales of the Daily Mail reports a popular Vietnamese restaurant in Brisbane‘s trendy West-End has been accused of disregarding food safety laws after it was searched by health inspectors.   

It come after eight diners were left with a bad taste in their mouth after claiming a visit to the restaurant gave them food poisoning.

Trang Restaurant has previously found fame being named Brisbane’s best Vietnamese food but the new allegations claim defrosting raw chicken found underneath a sink was allegedly among discoveries made by inspectors during a visit to the premises.

Despite the allegations of contempt for food safety laws, Trang has retained a largely satisfied customer-base

The allegations come as council health inspectors filed a complaint in the Brisbane’s Magistrate’s Court accusing the eatery of skimping on food safety laws.

The Courier Mail also reports complaints filed in late February included sightings of infected food, which was found throughout the restaurant. 

It is thought the raid was catalysed by eight diners allegedly contracting salmonella after eating at the restaurant between February and March this year. 

Handling eggs that have been recalled

When there’s a recall of 200 million eggs there’s a food waste/risk conversation. Telling folks to just cook them isn’t the full story. What about cross-contamination? How about a family with an immunocompromised individual? If there’s something special about the eggs (and by special I mean that they’ve led to over 20 illnesses) I don’t really want to have to make the call to handle it extra special. I like to think that I take lots of precautions with eggs (cooked until set, careful to not cross-contaminate) but what if I make a mistake. 

It’s not worth the risk. Take ’em back. That’s what I told Rachael Rettner from Live Science:

Having that [contaminated] product means I have to make no mistakes” when preparing the food, he told Live Science. In addition to undercooking, there’s a risk that consumers could cross-contaminate parts of their kitchen with Salmonella if they aren’t careful. “I would rather just not have that product … knowing it’s a risk of contamination,” 

Falconry as an option for pest control on farms

I’m a fan of the creative approach to using falcons to control wild pests on farms; with the caveat of balancing tradeoffs.

Back when I was doing on farm food safety stuff in greenhouses in Ontario (that’s in Canada) I had many farmers tell me that cats controlled the mice. They often asked what what’s worse – cat poop and feline tracking pathogens on their feet, or rodents everywhere. I never really had a good answer (and suggested traps for the the rodents). Today I saw an article form New Food Economy on using falcons as pest control on ranches and farms, with the click-worthy headline of ‘Could falcons prevent the next salmonella outbreak?’

Not if it’s linked to chicken eggs.

Maybe there’s some merit to the controlling-the-wild-with-the-trained approach, but in the absence of falcon diapers (as Don Schaffner suggested on Twitter) what’s the risk benefit tradeoff related to adding falcon poop into the mix. Maybe vaccination is the key (but I don’t know).

Wildlife biologist Paula Rivadeneira knows feces can be funny. Informally known as Paula the Poop Doctor (@PaulaThePoopDr on Twitter), she’s no stranger to the poop-based pun. Her SCATT lab—that’s Super Cool Agricultural Testing and Teaching lab to you—is a mobile research center inside a bus-sized RV, one she uses in Arizona’s crop fields to makes scat (animal droppings) scat (go away). But she also knows when poop stops being funny: if it gets into the food supply.

A simple, everyday fence can help dispel rodents and ground-based mammals. But how do you keep wild birds away from the open, vast expanse of a crop field? Over the years, farmers have struggled to find workable, cost-effective methods. Netting is too expensive and cumbersome. Chemical repellants can have taste and human health implications. A range of options exist to frighten birds away, from old-fashioned scarecrows and taped distress calls to deafening noise cannons, “exploders,” and sirens, but none are consistently reliable.

Which is where Rivadeneira comes in. As a specialist for the University of Arizona’s cooperative extension, it’s her job to find new ways to keep crop fields safely poop-free. Recently, she’s been at the forefront of a surprising new food safety initiative, one that—somewhat counterintuitively—entails bringing more birds onto agricultural lands. Rather than barricade, poison, or blast interlopers away, she’s helping farmers police their fields with the aid of an unusual ally: trained falcons.

22 sick: Over 200M eggs recalled by Rose Acre Farms

Rose Acre Farms of Seymour, Indiana, the second largest egg producer in the United States, is voluntarily recalling 206,749,248 eggs because they have the potential to be contaminated with Salmonella Braenderup.

The eggs were distributed from the farm in Hyde County, North Carolina and reached consumers in: Colorado, Florida, New Jersey, New York, North Carolina, Pennsylvania, South Carolina, Virginia, and West Virginia through retail stores and restaurants via direct delivery.

22 illnesses have been reported to date. 

The affected eggs, from plant number P-1065 with the Julian date range of 011 through date of 102 printed on either the side portion or the principal side of the carton or package.

The voluntary recall was a result of some illnesses reported on the U.S. East Coast, which led to extensive interviews and eventually a thorough FDA inspection of the Hyde County farm, which produces 2.3 million eggs a day. The facility includes 3 million laying hens with a USDA inspector on-site daily. 

Their own PR says 22 sick people, and then, “some illnesses.” Outpouring of corporate empathy there. And the USDA inspector on site means …?

Going public, Salmonella-in-French-cheese-style: Morbier and Mont d’Or cheese behind 10 deaths in France, 2015-16

In a country where reporting foodborne illness is deemed unpatriotic an investigation by France Inter radio revealed that at least 10 people died in the Franche-Comté region in the east of France linked to two cheeses made from unpasteurized milk  in late 2015 and early 2016.

The investigation produced a document which showed that in January 2016 national health authorities had discovered an unusually high number of salmonella contaminations in France that was centred on Franche-Comté.

Five cheese making companies in the region, between them making 60 different brands, were later identified as being at the source of the contaminations that began in November 2015 and continued until April the following year.

In a way that is truly French in its description, those who died in the outbreak were old people who were physically weak or who suffered from another illness.

Jean-Yves Mano, the president of the CLCV consumer association, said he was surprised that a product recall had not been ordered of products that might have been infected with salmonella.

“We do not understand why a general alert was not issued by state officials, or at least information given on what precautions to take,” he told France Inter.

The state food agency, the Direction générale de l’alimentation (DGAL), said there were two reasons why a recall was not ordered.

The first was that it would have allegedly been very difficult to identify which exact brand of the cheeses were contaminated because there were a total of 60 that were produced in the cheese-making firms where the outbreak originated.

The second was that by the time the authorities found out where the outbreak had come from, the contaminated cheeses had already been consumed and the new batches in the cheesemakers’ premises were not infected.

“It is perhaps due to these two factors that this contamination was not in the media, even though all the data was public nothing was hidden,” said Fany Molin of the DGAL food agency.

That’s French-bureau-speak.

Go public: Further illnesses may be prevented; others learn; citizens may not come with torches demanding change; and it’s the right thing to do.

Going public: Early disclosure of food risks for the benefit of public health

Mar.17

NEHA, Volume 79.7, Pages 8-14

Benjamin Chapman, Maria Sol Erdozaim, Douglas Powell

http://www.neha.org/node/58904

Often during an outbreak of foodborne illness, there are health officials who have data indicating that there is a risk prior to notifying the public. During the lag period between the first public health signal and some release of public information, there are decision makers who are weighing evidence with the impacts of going public. Multiple agencies and analysts have lamented that there is not a common playbook or decision tree for how public health agencies determine what information to release and when. Regularly, health authorities suggest that how and when public information is released is evaluated on a case-by-case basis without sharing the steps and criteria used to make decisions. Information provision on its own is not enough. Risk communication, to be effective and grounded in behavior theory, should provide control measure options for risk management decisions. There is no indication in the literature that consumers benefit from paternalistic protection decisions to guard against information overload. A review of the risk communication literature related to outbreaks, as well as case studies of actual incidents, are explored and a blueprint for health authorities to follow is provided.

Understanding egg nanostructure to enhance food safety

Fertilized chicken eggs manage to resist fracture from the outside, yet are weak enough to break from the inside during chick hatching. It’s all in the eggshell’s nanostructure, according to a new study led by McGill University scientists.

The findings, reported in Science Advances, could have important implications for food safety in the agro-industry.

Birds have benefited from millions of years of evolution to make the perfect eggshell, a thin, protective biomineralized chamber for embryonic growth that contains all the nutrients required for the growth of a baby chick. The shell, being not too strong, but also not too weak, is resistant to fracture until it’s time for hatching.

But what exactly gives bird eggshells these unique features?

To find out, Marc McKee’s research team in McGill’s Faculty of Dentistry, together with Richard Chromik’s group in Engineering and other colleagues, used new sample-preparation techniques to expose the interior of the eggshells to study their molecular nanostructure and mechanical properties.

“Eggshells are notoriously difficult to study by traditional means, because they easily break when we try to make a thin slice for imaging by electron microscopy,” says McKee, who is also a professor in McGill’s Department of Anatomy and Cell Biology.

“Thanks to a new focused-ion beam sectioning system recently obtained by McGill’s Facility for Electron Microscopy Research, we were able to accurately and thinly cut the sample and image the interior of the shell.”

Eggshells are made of both inorganic and organic matter, this being calcium-containing mineral and abundant proteins. Graduate student Dimitra Athanasiadou, the study’s first author, found that a factor determining shell strength is the presence of nanostructured mineral associated with osteopontin, an eggshell protein also found in composite biological materials such as bone.

The results also provide insight into the biology and development of chicken embryos in fertilized and incubated eggs. Eggs are sufficiently hard when laid and during brooding to protect them from breaking. As the chick grows inside the eggshell, it needs calcium to form its bones. During egg incubation, the inner portion of the shell dissolves to provide this mineral ion supply, while at the same time weakening the shell enough to be broken by the hatching chick. Using atomic force microscopy, and electron and X-ray imaging methods, Professor McKee’s team of collaborators found that this dual-function relationship is possible thanks to minute changes in the shell’s nanostructure that occurs during egg incubation.

In parallel experiments, the researchers were also able to re-create a nanostructure similar to that which they discovered in the shell by adding osteopontin to mineral crystals grown in the lab. Professor McKee believes that a better understanding of the role of proteins in the calcification events that drive eggshell hardening and strength through biomineralization could have important implications for food safety.

“About 10-20% of chicken eggs break or crack, which increases the risk of Salmonella poisoning,” says McKee. “Understanding how mineral nanostructure contributes to shell strength will allow for selection of genetic traits in laying hens to produce consistently stronger eggs for enhanced food safety.”

WGS links Salmonella in egg outbreaks in Australia

Building on their work with whole genome sequencing and eggs – because there’s a lot of outbreaks of Salmonella in eggs — a group of Australian researchers have reported on seven outbreaks of Salmonella Typhimurium multilocus variable-number tandem-repeat analysis (MLVA) 03-26-13-08-523 (European convention 2-24-12-7-0212) in three Australian states and territories investigated between November 2015 and March 2016.

We identified a common egg grading facility in five of the outbreaks. While no Salmonella Typhimurium was detected at the grading facility and eggs could not be traced back to a particular farm, whole genome sequencing (WGS) of isolates from cases from all seven outbreaks indicated a common source. WGS was able to provide higher discriminatory power than MLVA and will likely link more Salmonella Typhimurium cases between states and territories in the future. National harmonization of Salmonella surveillance is important for effective implementation of WGS for Salmonella outbreak investigations.

Seven Salmonella Typhimurium outbreaks in Australia linked by trace-back and whole genome sequencing

Foodborne Pathogens and Disease, March, 2018, 10.1089/fpd.2017.2353

Laura Ford Qinning Wang Russell Stafford,Kelly-Anne Ressler, Sophie Norton, Craig Shadbolt, Kirsty Hope, Neil Franklin, Radomir Krsteski, Adrienne Carswell,Glen P. Carter, Torsten Seemann,Peter Howard, Mary Valcanis,10 Cristina Fabiola Sotomayor Castillo, John Bates, Kathryn Glass,Deborah A. Williamson, Vitali Sintchenko, Benjamin P. Howden and Martyn D. Kirk1