UTI causing bacteria `steal` copper from host to defend themselves

Researchers, including one of Indian origin, have found that urinary tract infection causing bacteria “know” that copper is a potent weapon against them, and hence they steal copper to prevent the metal from being used against them.

According to researchers at Washington University School of Medicine in St. Louis., blocking this thievery with a drug may significantly improve patients’ chances of fighting off infections.

“While some patients are able to clear these infections without issue, in others the infection persists or recurs despite antibiotic therapy,” Jeff Henderson, senior author of the study, said.

“In some cases, the infection spreads to the kidney or the blood and becomes life-threatening. We’ve been investigating what’s different about the bacteria that cause these more troublesome infections,” Henderson said.

Scientists have known for years that E. coli makes a molecule called yersiniabactin that takes iron from host cells. The bacteria need the iron to grow and reproduce.

In earlier research, Henderson found that the E. coli that cause serious infections are more likely to make yersiniabactin.

This finding and the fact that E. coli already produce another molecule that steals iron led Henderson and Kaveri Chaturvedi, a student in his laboratory, to suspect that the bacterium might be using yersiniabactin for other purposes.

To test the theory, the researchers put yersiniabactin in urine samples from healthy patients.

They found the molecule bound iron as expected but also picked up copper.

Next, they conducted the same analysis in samples from patients with urinary tract infections who were treated at the University of Washington in Seattle.

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“We found copper bound to yersiniabactin in nearly every patient whose bacteria made the molecule,” Henderson said.

“Yersiniabactin was often bound to copper more than it was to iron,” he said.

When researchers put E. coli in the same test tube with copper, the bacteria that made yersiniabactin were more likely to survive.

Copper’s microbe-fighting properties were recognized long before scientists had described the microbes that cause infection. Ancient Greeks and Egyptians knew that treating wounds with copper improved the healing process.

Modern researchers have two explanations for copper’s anti-microbial effects – the metal can stimulate production of other chemically reactive molecules that damage bacteria; and it is also directly toxic to the bacteria.

The study has been published online in Nature Chemical Biology.

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