Tag: bacteria

Scientific testing of the ‘5 second rule’ of food on the floor

On By A.P.In MedicineLeave a comment

The five-second rule is based on the not-entirely-scientific belief that bacteria cannot contaminate food within five seconds, so you won’t get sick eating things you have picked up from the floor.

The first person to investigate this urban myth scientifically was Jillian Clarke, an American high-school student, during an apprenticeship in a microbiology laboratory at the University of Illinois in 2003. Clarke and her colleagues inoculated rough and smooth tiles with the bacterium E coli (certain strains of which cause stomach cramps, diarrhoea and vomiting) and put gummy bears or cookies on the tiles for five seconds. She found that E coli was transferred to gummy bears within five seconds, more so from smooth than rough tiles. As a side issue, Clarke also established in her work that university floors are remarkably clean and that people are more likely to pick up cookies from the floor than cauliflower.

Paul Dawson, professor of food science at Clemson University in South Carolina is a five-second-rule expert. His 2007 study, published in the Journal of Applied Microbiology, found that the dirtiness of the floor was more important than how long the food lay on it. His study was a progression from Clarke’s because it measured the amount of contamination. Using bread or bologna, he showed that it was better to drop either of them on carpet inoculated with salmonella, where less than 1% of the bacteria were transferred, than on tiles or wood, where up to 70% got on to the food. A similar study from Aston University found that, as soon as food hit the floor, it became contaminated – especially on smooth surfaces – but that the number of bacteria on the food increased up to 10 times between lying from three seconds to 30 seconds on the floor.

Dawson says that the five-second rule is simply not true because, if food hits a virulent brand of E coli, even the small number of bacteria it attracts immediately will make you sick. He doesn’t eat food when it falls on the floor. The very young or old shouldn’t use the five-second rule as their immune systems may not cope with even tiny amounts of bacteria. If the floor is filthy, then the rule is invalid on the grounds of grossness anyway. But the likelihood is that, for most of us, eating food off the floor isn’t going to hurt us. So if you are very hungry and you must pick food off the floor, then do it quickly, and preferably off a carpet.

http://www.theguardian.com/lifeandstyle/2015/sep/28/is-the-five-second-food-rule-really-true?channel=us

Keeping gut bacteria in balance could help delay age-related diseases

On By A.P.In ageing, aging, gut, gut bacteria, MedicineLeave a comment

Why do some people remain healthy into their 80s and beyond, while others age faster and suffer serious diseases decades earlier? New research led by UCLA life scientists may produce a new way to answer that question—and an approach that could help delay declines in health.

Specifically, the study suggests that analyzing intestinal bacteria could be a promising way to predict health outcomes as we age.

The researchers discovered changes within intestinal microbes that precede and predict the death of fruit flies. The findings were published in the open-source journal Cell Reports.

“Age-onset decline is very tightly linked to changes within the community of gut microbes,” said David Walker, a UCLA professor of integrative biology and physiology, and senior author of the research. “With age, the number of bacterial cells increase substantially and the composition of bacterial groups changes.”

The study used fruit flies in part because although their typical life span is just eight weeks, some live to the age equivalent of humans’ 80s and 90s, while others age and die much younger. In addition, scientists have identified all of the fruit fly’s genes and know how to switch individual ones on and off.

In a previous study, the UCLA researchers discovered that five or six days before flies died, their intestinal tracts became more permeable and started leaking.

In the latest research, which analyzed more than 10,000 female flies, the scientists found that they were able to detect bacterial changes in the intestine before the leaking began. As part of the study, some fruit flies were given antibiotics that significantly reduce bacterial levels in the intestine; the study found that the antibiotics prevented the age-related increase in bacteria levels and improved intestinal function during aging.

The biologists also showed that reducing bacterial levels in old flies can significantly prolong their life span.

“When we prevented the changes in the intestinal microbiota that were linked to the flies’ imminent death by feeding them antibiotics, we dramatically extended their lives and improved their health,” Walker said. (Microbiota are the bacteria and other microorganisms that are abundant in humans, other mammals, fruit flies and many other animals.)

Flies with leaky intestines that were given antibiotics lived an average of 20 days after the leaking began—a substantial part of the animal’s life span. On average, flies with leaky intestines that did not receive antibiotics died within a week.

The intestine acts as a barrier to protect our organs and tissue from environmental damage.

“The health of the intestine—in particular the maintenance of the barrier protecting the rest of the body from the contents of the gut—is very important and might break down with aging,” said Rebecca Clark, the study’s lead author. Clark was a UCLA postdoctoral scholar when the research was conducted and is now a lecturer at England’s Durham University.

The biologists collaborated with William Ja, an assistant professor at Florida’s Scripps Research Institute, and Ryuichi Yamada, a postdoctoral research associate in Ja’s laboratory, to produce an additional group of flies that were completely germ-free, with no intestinal microbes. Those flies showed a very dramatic delay in intestinal damage, and they lived for about 80 days, approximately one-and-a-half times as long as the animal’s typical life span.

Scientists have recently begun to connect a wide variety of diseases, including diabetes and Parkinson’s, among many others, to changes in the microbiota, but they do not yet know exactly what healthy microbiota look like.

“One of the big questions in the biology of aging relates to the large variation in how we age and how long we live,” said Walker, who added that scientific interest in intestinal microbes has exploded in the last five years.

When a fruit fly’s intestine begins to leak, its immune response increases substantially and chronically throughout its body. Chronic immune activation is linked with age-related diseases in people as well, Walker said.

Walker said that the study could lead to realistic ways for scientists to intervene in the aging process and delay the onset of Parkinson’s disease, Alzheimer’s disease, cancer, stroke, cardiovascular disease, diabetes and other diseases of aging—although such progress could take many years, he said.