Don't dose friendly bacteria with antibiotics

Yes, this is a trick question. But follow your gut instinct.What part of your body weighs in at about 3 pounds, contains tens of trillions of cells -- more than 5,000 different types -- and is probably unique in each individual? One more hint -- hates antibiotics.The answer: the spectacular array of bacteria and even more primitive archea that inhabit our intestines, fondly known among the many scientists studying them as our gut flora.Spread out over an intestinal lining with a surface area about the size of a tennis court, our symbiotic bugs are with us throughout our lives. They eat what we can't of the food we ingest. Without them, we would soon starve, since it is the bacteria that break down complex sugars and many other foods into smaller molecules we can absorb and use."It's truly a mutually beneficial relationship. We provide the bacteria with food and, in return, they supply energy and nutrients," said Dr. Masashi Yanagisawa, a professor of molecular genetics at the University of Texas Southwestern Medical Center in Dallas, studying how gut bacteria activate other bodily systems in their hosts.The microbes also activate our immune system, produce nutrients, like vitamin K (vital for blood clotting), that we can't on our own, and, it appears, dictate to some extent whether we're fat or skinny, in a good mood or bad, perhaps even set us up for some types of neurological disorders and inflammatory illnesses well beyond the digestive tract.In fact, some researchers delving into the microbes are starting to refer to them collectively as an organ, or pseudo organ, which needs to be monitored, maintained -- and manipulated -- to preserve and enhance health.It's important to note, though, that while environment and genetics play a role, our gut bacteria are largely reflective of what we eat: a diet heavy on the sugars favors some bacteria over others, and apparently not in a good way, while a diet big on fiber and veggies brings other types of bacteria into dominance.Yanagisawa's team, in a report published online last month in the Proceedings of the National Academy of Sciences, worked with mice (all animals have a similar colony of gut bacteria) to identify a molecule in the intestinal wall that's activated by waste products from the bacteria. Switched on, it slows movement of food through the intestine; giving it time to absorb more nutrients and thus a weight gain. When it's turned off, the animals weigh less. An earlier study by another team had also noted that mice with more gut bacteria had higher levels of body fat.The Texas researchers tested the relationship in two ways -- raising mice in a germ-free setting so they lacked bacteria and genetically engineering other mice to lack the molecule that reacts to bacteria. Both sets of mice weighed less and had a leaner build than a control group, even though they all ate the same amount.The researchers are hopeful that the molecule can eventually be blocked by a drug that would slow down calorie intake by moving food through the intestine at a faster clip.More recently, researchers at Stanford University and the Marine Biological Laboratory at Woods Hole, Mass., used a new system of genetic tagging to carry out the most comprehensive inventory of gut bacteria yet done. The work appears in journals published by the Public Library of Science.DNA analysis from human stools found the community in our digestive tracts is about 10 times more diverse than had been seen in earlier research -- more than 5,600 different species and strains (although some samples had as little as half that much variety).The second half of the study helps explain some of the variation. It may be caused by the bacterial A-bombs -- antibiotics -- that many people take with alarming regularity.After establishing a bacterial baseline, the researchers had three healthy humans take the antibiotic Ciprofloxacin for five days. A recheck of their gut bacteria afterward found that the population of about 30 percent of all species had plummeted.Further tests showed it took four weeks for most bacteria colonies to recover, and some hadn't bounced back after six months. Yet none of the subjects reported any gut-related problems -- probably because other types of bacteria unfazed by Cipro took up the digestive slack.However, the researchers suspect that long-term, repeated dosing with antibiotics may result in long-term disruptions of the gut ecosystem that may put at least some people at greater risk for disease or dysfunction in the bowels or elsewhere in the body. But now, researchers are at least in a better position to look for the changes.On the Net: http://www.pnas.orgwww.plos.orE-mail Scripps Howard News Service health and science reporter Lee Bowman at bowmanl(at)shns.com.