Category Archives: You are what you eat
It’s been a while since I have reviewed the various risks associated with eating, but I came across this Salmonella menace a few weeks ago. The Centers for Disease Control and Prevention published a case study describing a multistate outbreak of Salmonella enterica serotype Chester due to frozen meals. In November the CDC reported that 44 people became ill in 18 states during the late spring of 2010. Molecular analysis of patient isolates indicated sole source contamination and questionnaires completed by the patients suggested that “brand A cheesy chicken and rice frozen meals” were responsible. Of the 43 patients who were followed up, 16 of them required hospitalization however no deaths were reported. On the strength of the epidemiological analysis, the company recalled the product from the shelves and the outbreak strain was identified in 8 unopened containers. Investigation into the source during the manufacturing process did not turn up any production deficiencies or a conclusive common contaminated ingredient supplier. The best guess was that a single poultry supplier was the source in the outbreak. What made this case novel was that this episode represents the first time that Salmonella enterica serotype Chester had been reported in a widespread foodborne disease outbreak.
Editorial notes by the CDC point out that there is little in the way of negligence in either the supplier or production procedures used to bring this product to market. Simple Google image searching showed that the dinner in the above graphic was the one recalled in this outbreak. The label clearly says “Keep Frozen–Must be cooked thoroughly” and is considered a “not ready to eat” meal, as opposed to the hugely convenient “heat and serve” meal. Organisms such as Salmonella enterica and Shiga toxin-producing Escherichia coli are not effectively killed by incompletely reheating in the microwave, and require actual cooking in order to render them inert. The instruction to “allow dinner to sit in the microwave for 1 minute” is also a critical part of the cooking process, and is frequently ignored by consumers. The CDC notes that this outbreak highlights the need to educate the public on safe food handling procedures, and the need to follow the instructions prior to eating these products. Consumers also, if using a microwave oven to cook these products, need to know the specifications of their appliances and to ensure that their microwave ovens are able to be safely used to cook these.
There is an interesting story that played on National Public Radio this morning, “Gut bacteria might guide the workings of our mind.” An audio link to the radio program can be found on their website. The story details work by Dr. Emeran Mayer, at the UCLA medical school. He has been working to correlate magnetic resonance imaging (MRI) scans with specific microbial fingerprints of gut flora from normal, random volunteers, and looking for areas of the brain that are associated with certain kinds of normal bacteria. The premise behind this is that the brain responds to hormonal and neurological cues from the gut, and the types of microorganisms in the gut play a direct role in the types of cues. Future directions for the research suggest that scientists might be able to modulate behavior by altering the types of gut bacteria (via probiotics) or by drugs that mimic the effects of the bacteria. One active area of research in this is towards correcting the effects of autism by altering the diet, an avenue that has already shown promise in mice. Other published research by Mayer has shown that sections of the brain associated with anxiety have been affected by probiotic diet. Findings such as these will continue to forcefully dispel the notion that our normal microbiota are not merely passengers on our bodies, but active participants influencing all aspects of our biology.
Click here to watch a video at NPR about this.
Long time readers of BIO230 know of my fascination with all things feces. One interesting idea is to use a fecal transplant from a healthy individual to someone with gastrointestinal disease as a potential treatment. There has been some excellent preliminary data that this is a useful approach, in particular for treatment of things like chronic Clostridium difficile infection. The premise is that an infusion of “normal” microorganisms will out compete and eliminate the pathogens in the digestive tract, resulting in recovery without the use of things like antibiotics. Indeed, the ability of C. difficile to form endospores makes that organism particularly resistant to antibiotic therapy, which is why some patients have problems clearing the infections even with long term antibiotic therapy.
The problems with fecal transplants have been several fold so far, and most have been related to collection and delivery. First, the organisms to be infused have to be to some degree tailored to the patient. It is better to acquire the normal microorganisms from a donor who would likely share a similar microbial makeup to the patient, and so a family member would be best. Quite frankly, I am pretty sure that I would not want a poop donation from a total stranger. Second, there is an “ick” factor associated with the process that requires either a feeding tube to bypass the stomach or else delivery via colonoscopy to put the donor organisms into the correct location. Passage of the donated material through the stomach would likely greatly reduce the viability of the microorganisms and diminish the effectiveness of the treatment.
A news update on Gizmodo reporting a CBSNews story details an innovation in fecal transplant technology, and summarizes research done by scientists at the University of Calgary. (Editorial note: I would take off points if I graded the CBSNews report, due to their egregious failure to underline or italicize the names of microorganisms!) The researchers treated 27 patients of persistent, antibiotic resistant C. difficile infections by administering donor microorganisms. The novelty of this approach was that the donor microorganisms (taken from a relative at home) were brought into the lab to be cleaned of food and other non-bacterial fecal material, and packaged into triple gel capsules before administering orally to the patients. The gel capsule allowed the donated microorganisms to get past the stomach, so that the capsules could dissolve in the intestines. One patient, a retired nurse’s aide who reported two years of debilitating gastrointestinal disease due to C. difficile, has been cured by the donor bacteria pills.
Currently, the treatments are essentially tailored by specific donors for each patient. Other gastroenterologists foresee the potential for “universal” donors who might be able to contribute organisms that might help many different, unrelated patients. Since the donated fecal material can be frozen and stored to produce “poop banks”. Alternatively, people might go for the Do It Yourself approach in order to avoid needing to deal with health insurance companies.
Via io9, a news alert about a huge multistate outbreak due to Salmonella. I’d be snarky in any summary I would put up, but is is unlikely that I would do as good of a job, so I will just refer everyone there. Please go read it! I would say that we can rest easy because the professionals are handling it, but that is not the case today. Wash your hands an extra time.
Update! Via CBSNews, apparently food monitoring workers at the CDC have been called back to work to deal with this. I only hope they will get paid.
Update 2! I have put up a placeholder post for the current flu season. As you might be able to tell, we don’t know how much flu there is, or where it is.
BIO230 correspondent Heather G sent me this link from the International Journal of Clinical Medicine, which details a fascinating case study of Gut Fermentation Syndrome. A 61 year old male presented with a long history of intoxication, however there were numerous times when it was clear that he had not been drinking. His blood alcohol levels were frequently noted to be 5 times over the legal limit. The episodes appeared to begin following treatment with antibiotics following surgery, and were more frequent after missing a meal or having a drink the night before. Exam by emergency room physicians in 2009 didn’t know of any way to become drunk without ingesting alcohol, and therefore assumed that he was a “closet” drinker. After referral to a gastroenterology practice in 2010, cultures of H. pylori were isolated from his stomach, and cultures of Saccharomyces cerevisiae and other yeasts were isolated from stool cultures. Following a controlled hospital stay where his blood alcohol levels were carefully monitored over the course of 24 hours following glucose challenge, it was concluded that the alcohol was being produced by his gut microorganisms.
Since this is a topic I could easily be passionate about, I decided to try and learn more. The article linked above had a brief review of the literature, and listed a few primary literature articles describing the phenomenon. My go-to citation finder at the National Library of Medicine was a bust, and turned up little of interest. A search of Google Scholar was perhaps a little bit more encouraging with the number of hits, however again most of the relevant items were not novel. Interestingly, most of the articles that I found dealing with alcohol and fermentation in the intestines dealt with the production of acetaldehyde from ethanol, which is in turn a potent carcinogen. In articles such as this one, the presence of alcohol in the upper digestive tract (presumably from long term alcohol consumption) acts as a substrate that can be further fermented by a variety of microorganisms into the terminal fermentation product acetaldehyde. This compound is strongly correlated with the development of tumors of the small intestine. The production of ethanol as a terminal fermentation product in the mammalian gastrointestinal system appears to be extremely uncommon.
All of the cases in the literature about the topic seem to have several things in common, and patients who develop the condition are typically on a unique diet which contains fermentable sugars, have a diminished bacterial gut flora due to antibiotic use, and have a unique mixture of yeasts which have in turn colonized their system. Fungi do make up an important part of the human gut flora, mainly Candida species, however I can find little evidence that Candida is able to produce ethanol as a terminal fermentation product. Most individuals who exhibit Gut Fermentation Syndrome appear to be colonized with a mixture of yeasts, including Saccharomyces cerevisiae. This is interesting in itself, as S. cerevisiae is a poor colonizer of the human body due to our body temperature, and few articles can be found describing this organism in a disease setting.
And so: an experiment for Science! We will need to start with the yeast. As I prefer a nice IPA, my searching indicates that something like yeast strain 1272 might be a good starter culture. We will need to get the organism adapted for growth in the human body, so we will have to do an enrichment culture at 37 degC, followed by assessment of alcohol production in vitro in the YCP Biology labs. Fortunately, we have in our possession a Vernier alcohol concentration probe, so this is trivial to accomplish. At this point, we will have two options in which to proceed. First, we could jump straight to human trials, however since most BIO230 students are under the age of 21, I think we will go with option two which is to conduct animal studies. We will use outbred CD-1 mice, and administer a broad spectrum oral antibiotic to reduce their normal gut flora, and repopulate with our new IPA yeast via the diet. Control animals will receive heat killed yeast in their diet. We also will administer one of two diets: either a normal rodent chow diet, or a diet which we have supplemented with fermentable sugars–this carbohydrate rich diet looks to be just what we would need. Mice which have been recolonized with our IPA yeast and fed the carb rich diet ought to exhibit behavioral traits that can be measured.
BONUS: For Bonus to be added to your course grade, suggest a method for assessing whether this works in vivo. Do not suggest having the mice recite the alphabet backwards, because unless you are these guys, it isn’t going to work.
Kristina Stefanik (12:00 Micro) found this article in Science Daily about the normal microbiota, human diet, and association with body mass index. Another summary of the research was recently up at Time.com. Here is Katrina’s report:
Just call me the next Dr. Oz (or Bill Nye); I’ve found the secret to becoming skinny! Unfortunately, it’s not in a food or a certain type of exercise…it’s in your breath. You saw it correctly…an indicator in your breath can reveal how likely or unlikely you are prone to weight gain. A study published in The Endocrine’s Society’s Journal of Clinical Endocrinology & Metabolism discovered that people whose breath contains increased concentrations of hydrogen and methane gases are more likely to have a higher body mass index and percentage of body fat. The presence of these two gases together strongly indicates the existence of a microorganism which supports obesity. It is better known as Methanobrevibacter smithii.
M. smithii takes up residence in the digestive tract- the prime site of absorption of nutrients. Earlier research confirms that this is the principal microorganism in the human gastrointestinal tract responsible for the majority of methane production. About 70% of people have these bacteria in their tract, while 30% have an elevated amount. Under normal circumstances, M. smithii in the digestive tract is viewed as beneficial. It helps us convert food into energy; however, the problem arises when the organism reaches excessive amounts. It operates as hunter for hydrogen emitted from other microbes and uses that hydrogen to produce the methane exhaled in our breath. The other microbes seemingly benefit from this relationship; they flourish and extract nutrients from food more effectively. Therefore, the higher amount of M. smithii, the more efficient the hydrogen-producing bacteria become. Over a long period of time, this uptake of excess nutrients contributes to weight gain. As stated in the article, this essentially allows a person to harvest more calories from their food.
The study analyzed the breath of 792 people. From this, four patterns appeared. The test subjects had normal breath content, increased content of hydrogen, higher concentrations of methane, or higher degrees of both gases. Accordingly, as the article states, the subjects who possessed higher concentrations of both gases had significantly higher body mass indexes and higher percentages of body fat. More specifically, their BMIs were about 2.4 points greater than those with normal levels of the gases and had about six percent more body fat on average.
Ruchi Mathur, MD, director of the Diabetes Outpatient Treatment and Education center, is continuing a study funded by the American Diabetes Association. As the Time article states, she is working with a group of overweight and obese pre-diabetics that tested positive for methane on their breath. Mathur and other researches will begin to test the participants’ glucose tolerance, measure how long it takes for food to travel through their intestinal tract, and take their stool to the lab to determine the amount of calories in it. After this has been established, the participants will then receive an antibiotic to kill the colonies of M. smithii. They will undergo the same procedure and will essentially be able to determine if eliminating the microbes will alter the person’s weight conditions and overall health. It is amazing to think about how something so small could have such a major impact on something like weight gain!