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Antibiotic Resistance Lurks in Your Gut; Scientists Film a Microbial Smackdown

Posted By Prucia Buscell, Thursday, September 3, 2009
Updated: Thursday, February 17, 2011

Researchers have discovered previously unknown genes for antibiotic resistance lurking in the human gut.

A story by Bob Grant in The Scientist reports that Harvard University researchers found more than 90 undiscovered bacterial genes capable of conferring antibiotic resistance in the intestinal tracts of two healthy adults. Humans have been exposed to quantities of antibiotics for decades through medicines and foods as well as by agricultural use and cleaning products. Morten Sommer, lead author of the study, published in Science, says the newly discovered antibiotic resistance in our internal microbiome is likely to result from that exposure. Sommer, a postdoctoral researcher in the lab of Harvard geneticist George Church, told The Scientist "that could be a problem when the microbiome interacts with disease causing microbes."

Sommer and colleagues isolated more than 500 bacterial strains in saliva and fecal samples from two healthy adults who had not taken antibiotics for at least a year. They cloned the genes from those strains and exposed them to 13 different antibiotics to discover which genes conferred antibiotic resistance. Stuart Levy, A Tufts University microbiologist who is president of the Alliance for the Prudent Use of Antibiotics, said the study highlights the dangers of pervasive irresponsible antibiotic use. He said pathogenic bacteria could add antibiotic resistance to their genes by way of horizontal gene transfer from harmless bacteria that has the resistance trait.

Research by Sommer and colleagues found nearly half the resistant genes isolated from the human gut are identical to resistant genes found in pathogenic microbial strains of E. coli and Salmonella enterica. While that doesn't prove horizontal gene transfer between beneficial gut bacteria and pathogens, Sommer said it does show a close evolutionary history. Sommer has also researched another discovery: bacteria that thrives by eating antibiotics.

The Scientist quotes Gerry Wright, a chemical biologist and infectious disease researcher at McMaster University, as saying the gut study shows how little is understood about microbial ecology and how antibiotics work. If resistance is so rampant, he asks, what makes antibiotics work at all?

Cellular Conflict

Researchers at the University of Bath and the University of Exeter in the United Kingdom have developed a new technique that lets them observe microbial cells in action. While most studies of infection have been done after the death of the infected organism, these scientists were able to make a movie of a bacteria infecting a living host. They also created an extraordinary film debut: the war between immune cells and hostile bacteria.Will Wood, research fellow and coauthor of the study, explained that cells behave differently in a Petri dish than they do in their natural environment, so it is important to be able to examine how bacteria interact with their host.

You can view the movie at the University of Bath website, and on the NPR where you can see the August 21 Science Roundup reel on Worms, Snorkels and Cell Battles. The microbial smack down is the last of the brief segments. But do watch the first two. They are fascinating, as Ira Flatow's Science Friday presentations generally are.

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