Science and Our Food Supply - Middle School Guide: Module 5 - Outbreak and Future Technology
MODULE 5 - OUTBREAK AND FUTURE TECHNOLOGY
Even though our food supply is the safest in the world, we face new challenges as we import food from all over the world, as new pathogens emerge, and as familiar ones grow resistant to treatment. Foods reaching your table today are produced, processed, and distributed very differently from even a decade ago. Food from a single source may be rapidly distributed to communities across the nation, making it more difficult to detect a disease outbreak caused by contaminated food. Just as food can now be rapidly distributed, technology is allowing us to keep track of foodborne outbreaks across the United States.
Using molecular technology and a sophisticated computer system, epidemiologists can now rapidly assess whether a widespread food incident is underway, and they can trace the source of the problem by identifying distinctive fingerprint patterns of pathogens like E. coli O157:H7.
PulseNet is a way scientists are able to link microorganisms from different places associated with an outbreak to see if they have a common origin. Local laboratories participating in PulseNet perform DNA fingerprinting on bacteria that have caused illness. Microbiologists extract DNA from the microorganism and then pulse an electrical current through that material. The pattern, or fingerprints, received by the currents is then transmitted through a networked computer system to the Centers for Disease Control and Prevention (CDC).
If patterns submitted by laboratories in different locations match, CDC computers will alert PulseNet participants of a possible multi-state outbreak. An investigation can begin immediately to trace the source of the problem and stop the outbreak. If the source is found, the food will be taken off the market and measures will be taken to prevent future outbreaks.
Dr. Solomon - the
Research scientists at USDA's Agricultural Research Service in Maryland had been requested to explore a theory that came from a retired nuclear weapons designer. The theory suggested that shock waves unleashed by an explosive set off in water could tenderize a piece of meat submerged in water.
To explore the concept, they put steel in the bottom of trashcans. Then they suspended meat in water inside the trashcans, buried the trashcans, and detonated explosives.
The shock waves created by the explosion travel through anything that is an acoustic match with the water, and tear anything that is not an acoustical match. Beef is about 75% water, and the muscle tissue and fat are not. Thus, the hydrodynamic pressure tenderizes the beef.
Along the way, scientists discovered that applying hydrodynamic pressure to the beef was not only tenderizing the meat, but also eliminating harmful bacteria by 40 to 60%. This discovery was an added bonus!
OUTBREAK ALERT (Shigella)
Time: One 45-minute class period
- Food-safety portfolios (for each student)
- Dr. X and the Quest for Food Safety video/DVD, Module 5 - Outbreak and Future Technology
Motivate your students with this scenario: You're sitting in your office. All of a sudden, red lights are flashing! You hear, "ring," "ring," "ring" all around you. What's going on? Then finally you realize that this flutter of red lights and constant ringing is your telephone - it's ringing off the hook. Could it be . . . an outbreak?
Continue to engage the students by telling them that they are FBI (FoodBorne Illness) Investigators in Suffolk County, New York. They've just received notice that 21 people in the county have become ill with similar symptoms (nausea, vomiting, diarrhea, cramps, and fever). The illnesses occurred over a 1-month period - from November 8 to December 8. The sick persons have tested positive for the Shigella bacterium. Ask: How would you investigate this case to find out how the outbreak got started?
- Divide the students into 3 or 4 groups.
- Inform students that as FBI (FoodBorne Illness) investigators, it's their job to work with their colleagues to identify the steps they would take to investigate this outbreak.
- Ask students: What do you know about this case? Have them analyze the existing data and record it in their food-safety portfolio in the form of the 5 "Ws" ("Who," "What," "Where," "When," and "Why," plus "How"). Note: 4 of the "Ws" were given in the teacher introduction.
- Who - 21 people who became ill
- What - Shigella bacterium
- Where - Suffolk County, New York
- When - November 8 to December 8
- Why - ?
- Challenge each team to discover more details about the case. They should come up with more specifics on each "W," then solve the "Why" and "How" of this case. For example:
- What is Shigella?
- How is Shigella transmitted?
- Where in Suffolk County could this outbreak have occurred?
- Ask students: What do you need to find out first? To help them along the way, students can conduct research about outbreaks and Shigella (see the Resources section). From time to time, you can also give them clues (see box at right for clues and the answers), but first allow the students to formulate their own strategies.
- Have the teams write up their steps. Make sure they number each step.
- Then have each group share their investigation steps and their conclusions with the class.
- Discuss and compile a class list of what would be the most probable conclusions as to where the outbreak occurred, who or what transmitted the Shigella bacterium, and why the outbreak occurred. Then ask: What would you do to correct the problem?
- After you have compiled the class list, review the real-life, step-by-step process that Public Health Officials in Suffolk County, New York, conducted. Compare the class approach and conclusions with the actual investigation. Are there similarities? Differences?
- Then have students discuss the questions in the Instant Replay below.
One person, working in a foodservice establishment, can infect multiple people if he or she doesn't follow safe food-handling practices, especially proper handwashing. Proper handwashing is one of the most important precautions in preventing bacteria from spreading from hands to foods. Everyone plays a role in keeping our food safe from harmful bacteria, including farmers, ranchers, distributors, manufacturers, foodservice managers, employees, and customers.
- In the Dr. X and the Quest for Food Safety video/DVD, you learned about PulseNet, a national network of local laboratories that performs DNA "fingerprinting" to better detect a foodborne outbreak in multiple states. Investigate the PulseNet Web site and prepare a report, including the following:
- What is PulseNet?
- How does DNA "fingerprinting" by PFGE work?
- How has DNA "fingerprinting" been used to prevent foodborne illness?
- Is PulseNet currently tracking your foodborne pathogen?
- How do you think PulseNet will change in the next 10 years? 20 years? 30 years?
- Write your own outbreak case and solution. Then act out the case and have the class investigate and solve it.
- Check out CDC's Food Safety Web site (click on "outbreak investigations") to see if your foodborne pathogen was involved in any recent foodborne illness outbreaks. Include any discoveries in your food-safety portfolio.
- Relate your pathogen to this activity and record the information in your food-safety portfolio.
See real-life scientists in action!
- Food Safety A to Z Reference Guide
HERE'S WHAT THE PUBLIC HEALTH OFFICIALS DID . . .
The Real-life Step-by-Step Investigation 1994 Shigella Outbreak in Suffolk County, New York
- Between November 8 and December 8, 1994, 21 people experiencing symptoms (nausea, vomiting, diarrhea, cramps, and fever) go to the doctor.
- Doctors make an initial diagnosis, and stool cultures from the patient are sent to a clinical laboratory.
- At the lab, medical tests are done on the stool cultures. The lab determines the presence of the Shigella bacterium.
- An isolate of the bacterial culture is sent to the state health department lab for further testing.
- The health department sends the results to the Bureau of Infectious Disease Control in Suffolk County.
- Due to the unusual cluster of cases, the Bureau realizes that this is not an isolated case, but an outbreak. On December 12, 1994, the investigation begins.
- Health officials interview the 21 sick people. They discover that 17 of the 21 people affected fell into one of three categories:
- They ate at the same fast-food restaurant 1 or 2 days prior to the symptoms occurring;
- They were members of a family who ate foods prepared at the restaurant 1 or 2 days before a family member became ill;
- They had close personal contact with families who had eaten at the restaurant 1 or 2 days before a family member became ill, but they did not, personally, eat at the restaurant.
Possible Location and Food Identified
- Officials give the affected families a questionnaire. Two of the 5 families return the questionnaire. The questionnaire reveals that 4 of the 5 families who had eaten at the restaurant developed symptoms within the 2-to-3 day incubation period. The fifth family had close personal contact with one of the families that had eaten at the restaurant. French fries were the only common food eaten by the sick people and their families.
- Health officials interview the employees who worked in the afternoon, because the suspect meals were served in the afternoon.
- Health officials take stool samples from the afternoon employees for bacteriological examination.
- Health officials inspect the restaurant. During the inspection, they discover that the rear kitchen handwashing sink and the customer and employee restrooms lack sanitary hand towels.
Location and Food Verified
- Health inspectors request that the restaurant's operators advise all employees who worked on thedays in question to submit to a stool sample. Four employees quit rather than submit a sample.
- Fifty-one stool samples were provided. All but 3 samples were negative. One was positive for Streptococcus, one was positive for Salmonella, and one was positive for Shigella. These 3 employees were restricted from work until 3 consecutive, negative stool samples were obtained. The one positive sample for Shigella was collected from the store manager who had first stated that he had not been ill. He later admitted that he had experienced gastrointestinal illness on December 8, 1994.
- When a positive Shigella was obtained from the manager, a copy of his work schedule was obtained to determine if he worked on the dates and times of the suspect meal. It was found that his work schedule matched 2 of the 4 suspect meals.
- The health department makes a conclusion that the illnesses originated at the restaurant based on the following factors:
- Shigella outbreaks are usually caused by sick food workers who, after using the bathroom, don't wash their hands and then handle food.
- The sick food worker first said that he was not sick and later stated that he experienced symptoms on December 8, 1994. This was several days after the last customer in the outbreak became sick, indicating that he may have been spreading the bacterium before he actually experienced the symptoms. The food worker may also have been mildly sick, but didn't realize it.
- French fries were the only product common to all the sick people. Normally, very little hand contact occurs in preparing and dispensing French fries, because the fries are scooped with a utensil. However, the product is handled by front-counter personnel who do not use disposable gloves as a barrier to hand contact with the food. It's not unusual for fries that fall out of the cardboard holders to be picked up with bare hands and tossed back into the French fry bin. Furthermore, the cardboard containers are stored flat and must be "opened" to accept fries. These containers are frequently opened and carried with bare hands that touch the outside and inside of the container.
Note: This investigation did not confirm the association between the restaurant and the Shigella bacterium. However, the bacteria test results and the presence of an employee in the restaurant who tested positive for the same type of Shigella that infected the families who ate at the restaurant, suggest that the outbreak was caused by foods eaten at the restaurant. Foodborne illness outbreaks are very difficult to track and public health officials can only draw conclusions based on the information they obtain from sick persons, food establishments, and test results.
Time: One 45-minute class period
- Make copies of Beef Blasters article and questionnaire for each student.
Begin this lesson by writing the term "Beef Blasters" on the board. Ask: What do you think of when you see this term? Would you eat a "Beef Blaster" Burger? How about a "Beef Blaster" steak?
No, it's not a new video game. It's a real process currently being researched to improve the safety of meat. You're going to be introduced to this interesting story, and it has a big surprise at the end!
- Divide students into 5 "expert" teams. Then distribute the Beef Blasters article with questions to each student.
- Assign each team 2 questions. Students will become the "experts" on these questions and share their knowledge with the rest of the class.
- Have each student in each team silently read the article. Then have them discuss and write down their answers to the questions.
- Have each team present their questions and answers to the class.
- Have a class discussion to explore all the answers
Scientists sometimes have unconventional ideas and test them in unique ways. This article was a great example of how serendipity and the personality of scientists sometimes play a major role in science discoveries, and it clearly illustrates that science is a human enterprise. In this case, in addition to discovering how to tenderize beef, the scientist found that shock waves also work to significantly reduce the amount of bacteria on and in the meat.
- Research additional examples in science or recent history where discoveries were made unexpectedly (e.g., Alexander Fleming and the discovery of penicillin, Louis Pasteur and the discovery of pasteurization, the 3M Post-It Notes invention, and NASA discoveries). Identify scientists who might be considered maverick thinkers and worked in unconventional ways.
- Give tentative explanations for how the shock waves kill harmful bacteria.
- Design a tool that could kill bacteria in a variety of foods. Give explanations as to why your technology might work.
- Learn more about Dr. Solomon's background and career (see the Food Safety A to Z Reference Guide Careers section).
See real-life scientists in action!
- Food Safety A to Z Reference Guide
By Wes Ishmael
Contributing Editor – Beef Magazine™ January 2000
You know it's going to be a tough day when your boss summons you to meet with the office brass and in come three agents from the FBI and three from Alcohol, Tobacco and Firearms (ATF). They immediately flash their badges and begin a no-nonsense interrogation about why you're trying to acquire explosives, and why none of your bosses know anything about it.
Never mind that you're a research scientist at USDA's 7,000-acre Agricultural Research Service (ARS) facility in Beltsville, MD, smack between Washington, DC, and Baltimore
Morse Solomon, research leader of the ARS meat science research laboratory, tried to explain to the agents that the explosives were for an experiment he was conducting at the request of the Secretary of Agriculture's office. They had requested his help designing an experiment to prove their Hydrodyne theory – that shock waves unleashed by an explosive set off in water would tenderize a piece of meat submerged in the same water.
"Who exactly called you from the Secretary's office?" asked the agents.
"I wrote it down, but I don't remember off the top of my head," said Solomon.
"Did you even verify that it was the Secretary's office?" wondered the agents.
"I didn't really see a reason to," replied Solomon.
"And who are you designing the experiment for? Who is trying to deliver explosives to you?" demanded the agents.
"Some guy named John Long."
"What's his background and how do we get hold of him?"
"I don't have any idea . . .," said Solomon.
In hindsight it's easy to understand how it was that Solomon left this interrogation as much of a suspected terrorist as John Long. Keep in mind, this ARS complex houses all kinds of pesky bacteria, parasites and the like. Plus, to meet Solomon is to believe his creative thoughts must come at the same frenetic pace as his conversation. It's easy to imagine him chasing down the bottom line without worrying about where a cache of explosives was coming from.
"Things weren't going well," remembers Solomon. "Plus, John is a very persistent guy, so he was still trying to get me the explosives."
Solomon wasn't familiar with the requirements for buying explosives. So when a supplier enlisted by Long contacted Solomon, his naivete was all too obvious. The suspicious supplier turned him into the FBI.
The government agents told Solomon they would monitor his activities as they tried to get a lead on this John Long fellow. They told him he could accept phone calls from Long but no packages. Solomon dodged Long's calls for two weeks. By this time, he was pondering his career prospects and his freedom.
What seemed like a lifetime later, Solomon was again called to the office of his boss's boss. This time there was just one FBI agent and one ATF agent.
"Let's try this again," said the agents. "Do you know who John Long is?"
"I still don't have any idea," said Solomon.
"Well, we do," said the agents, finally smiling. Turns out, Long is a retired CIA weapons designer with Pentagon clearance; he used to design nuclear weapons. He and his partner tracked Solomon down via a former Assistant Secretary of Agriculture. They and their Hydrodyne idea were for real.
Launching A New Idea
Since meeting Long in 1992, Solomon has heard several versions of how Long first conceived of tenderizing meat with explosives back in the '60s. Suffice it to say, by the time Solomon entered the picture, Long had his Hydrodyne process and a prototype already patented.
The device today is a 7,000-lb. steel tank that holds 282 gals. of water and 400–600 lbs. of meat. The meat is bagged and submerged in the tank. An explosive is suspended over the top of the meat, then detonated.
But Solomon was far from knowing all of this when he traveled to an off-site location in Virginia, armed with meat, to witness his first Hydrodyne "shot" at tenderization. He was still skeptical.
When Solomon arrived and saw these would-be pioneers taking rubber trash cans out of their car, he said, "No, no, that's alright. I've already got the meat in a cooler, we don't need those."
"No, you don't understand," they said, "This is our hydrodyne unit. There is no reason to build the one you saw the picture of until we know that this works."
Solomon's heart could have slipped beneath an ant's belly with room to spare. He believed the machine already existed, that his experiment and expertise were only to determine how well the process worked.
They buried the trash cans, detonated the explosives and raced back to the lab to see the results. "It didn't work," says Solomon. "There wasn't any change in the meat at all."
Long made a quick phone call to a physicist friend. Bemusedly, that friend informed him there was no way the process would work without steel in the container for shock-wave reverberation.
They tried again, with steel in the bottom of the trash cans. The results were incredible. Basically, Solomon says you can take tough steaks, as measured by Warner-Bratzler shear force and, under the right conditions, hydrodynamic pressure technology can make them eat as tender as filet.
"The meat is softer than normal when you take it out, but it firms back up in the cooler," says Solomon. In taste panel work conducted by ARS researcher Brad Berry, consumers detect the change in tenderness but no differences in flavor or juiciness. Solomon adds, "In some studies with salted meat (kosher processing), we've found this process also helps preserve the cherry red color."
In round numbers, Solomon explains they've seen everything from a 20% to 60% increase in tenderness. Part of that has to do with how tender the meat is to begin with. The process will not over-tenderize meat, so it will not add anything to meat that is already tender.
What's more, Solomon points out, "With this process, not only does it reduce shear force values, but it flattens out the tenderness variation across the steak, making it consistently more tender."
For the record, Solomon says, the shock waves work because meat, beef in this case, is 75% water. "The shock waves travel through anything that is an acoustic match with the water (the water in the beef). The things that are not an acoustic match (muscle tissue and intramuscular fat) are torn. That's why the cuts have to be boneless or semi-boneless.
The shock waves shatter the bone and over-tenderize the tissue next to it," he says.
Armed with successful results, Long and his business partners formed a company and constructed a $1.6 million prototype. He's now working apart from ARS to perfect the process. At the same time, Solomon and his research team continue to do their own experiments with a scaled down version of the prototype and those trusty trash cans.
The Rest Is History, Almost
With more steel in the actual Hydrodyne unit, researchers believed its performance had to outpace the trash cans. So far, it hasn't. Researchers reduced shear force 37–57% in the original metal prototype, but effectiveness lessened as structural changes were made to accommodate the force of the explosions. The last time Solomon tested the modified unit, tenderness gains had dropped to 12–24%. All the while, the venerable trash can is increasing tenderness 33–67%.
The jury is still out, but explosives experts from the army and navy think the differential may have to do with the fact that the sides of the trash can actually explode out, while an implosion occurs in the self-contained unit. The theory is that the explosion conjures up a shock wave three times more powerful than the implosion.
As private industry and ARS wrestle with the differences, Solomon and his crew uncovered something even more startling. With an added tweak, the process destroys pathogens.
"Food safety is a bigger issue than tenderness, and we're getting a 40–60%* reduction in bacteria load with hydrodynamic pressure technology," says Solomon. That, plus increased tenderness for an estimated 8–10¢/lb.
Understandably, Solomon says meat processors are excited about the prospects, especially considering how well Hydrodynamic pressure stacks up when compared to other postmortem technologies that require aging. But, Solomon says they're not thrilled with a batch system unless the batch could be at least 10 times larger than the 600 lbs. of meat held by the current prototype.
With that in mind, Solomon and his team of research scientists envision an inline system that would preserve the added effectiveness of the trash can explosion. He believes commercial application may be only two years away.
If it does become reality, chalk it up as a good day for the U.S. beef industry, and a long haul for one scientist who dodged the long arm of the law to make it possible.
* Meat samples were examined immediately after HDP treatment. Shelf-life bacterial populations in the samples showed a 3-log reduction (for example, they decreased from 300,000 colony-forming units to 300). Agricultural Research/December 2000
Answer the following questions with your team:
- What's the science behind this story?
- Do you consider Dr. Morse Solomon a scientist or an engineer? Explain.
- What do you think are the characteristics of a scientist?
- What's the twist of science in relation to how research is conducted at the beginning of a study compared to the end results?
- Do you know of any other examples in science or recent history where discoveries were made unexpectedly? Explain.
- How do scientists get their ideas? 7. What's the inter-relationship of the different sciences in reference to this experiment?
- How does a scientist prove a theory to be correct? Who and by what means is it proven correct?
- What happens after a scientist proves a theory to be correct? How does that theory become a reality and get put to use?
- How do Dr. Solomon's experiments relate to you?