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Antibiotic-Eating Germs Could Be Bad News for Immune System

Posted on: Friday, 4 April 2008, 05:10 CDT

Researchers have found that certain strains of bacteria in the soil are literally consuming potent antibiotics - thriving from the potent drugs as their sole source of nutrients.

Scientists are looking to understand how these bacteria outwit antibiotics so that the more dangerous germs that cause illness in people don’t develop the same ability.

Soil microbes taken from 11 sites uncovered bacteria that could withstand antibiotics 50 times stronger than the standard for bacterial resistance, the study found.

"Many bacteria in many different soil isolates can not only tolerate antibiotics, they can actually live on them as their sole source of nutrition," said George Church, a geneticist at Harvard Medical School in Boston, whose research appears in the journal Science.

Researchers have known that bacteria can withstand some antibiotics; some had already been found. A number of antibiotics are natural, like penicillin. Many important antibiotics have come directly from the soil.

The surprising discovery was how many bacteria didn't just survive but flourished when fed 18 different antibiotics, natural and manmade ones - including such staples as gentamicin, vancomycin and Cipro - that represent the major classes used in treating people and animals.

Church’s study offers more clues about why bacteria quickly develop resistance to antibiotics, and why drug companies must constantly develop new antibiotics to defeat them.

The research showed that a number of bacteria could withstand levels of antibiotics that were 50 to 100 times higher than would be given to a patient.

"They were not only resistant, they were super-resistant," Church said.

The bacteria were not known to attack humans . However, some were close relatives, such as members of the Burkholderia cepacia complex, a group of bacteria that infect people with cystic fibrosis, and Serratia marcescens, which can cause blood infections in people with compromised immune systems.

The finding comes amid increasing concern that many infections could soon become untreatable, as more bacteria become immune to today's antibiotics even as few new drugs are being discovered.

According to Church, the finding underscores the extent to which bacteria have developed resistance to antibiotics, a process that started almost as soon as penicillin was introduced in the 1940s. Overuse and misuse of antibiotics have since fueled the rise of drug-resistant superbugs.

He said the microbes they found may be using a new way to disarm the antibiotics, but it may take some time to figure that out.

“Gene pathways involved in metabolism are far larger and more complex than the type of single-gene resistance often seen in human pathogens,” said bacteriologist Jo Handelsman of the University of Wisconsin-Madison, who wasn't involved in the study.

Church agrees: “it’s not entirely all bad news. ... It gives us some time to get ahead of it and figure out if it really poses a threat."

Antibiotic resistant infection, caused by a strain known as methicillin-resistant Staphylococcus aureus, or MRSA, is blamed for killing 19,000 people in the United States in 2005.

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Harvard Medical School

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Source: redOrbit Staff and Wire Reports

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