Researchers Use Gallium As Trojan Horse Against Bacteria

By Nicholas Gerbis
Published: Wednesday, September 26, 2018 - 11:10am
Updated: Wednesday, September 26, 2018 - 12:50pm

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Singh Lab/University of Washington
Colonies of Pseudomonas bacteria growing on an agar plate.

Each year, 2 million people in the U.S. develop an antibiotic-resistant infection, and 23,000 die from one, according to the Centers for Disease Control and Prevention. The current crisis is inspiring some researchers to revisit old ideas.

In the 1800s, Louis Pasteur argued that scientists could fight bacteria by disrupting their nutrition.

Now, mouse studies and a small, preliminary human trial suggest that gallium, best known for its use in semiconductors, can do just that.

"The bacteria confuse gallium for iron, use their importers to take it up into the cell, and then, once inside the bacteria, the gallium wreaks havoc and acts kind of as a poison," said Pradeep Singh of the University of Washington School of Medicine in Seattle, a coauthor on the study.

The Trojan horse works because gallium is structurally similar to iron.

The paper appeared in the journal "Science Translational Medicine."

Intravenous gallium nitrate is already used to treat a noninfectious illness: hypercalcemia of malignancy, a complication of some cancers that causes patients to develop a dangerous overabundance of calcium in the blood.

The human clinical study involved subjects with mild cystic fibrosis or chronic Pseudomonas aeruginosa lung infections. It used no blinds or placebos.

The researchers emphasize that larger, more rigorous human and animal trials are needed, but say that, so far, gallium appears to be a safe and effective alternative to standard antibiotics.

Moreover, gallium's effects are likely not limited to the bacteria in the current study.

"We've seen some in vitro evidence, or laboratory based evidence, that gallium has activity against a number of other important human pathogens, and so we do hope to do additional animal studies to get proof-of- principle to suggest that gallium might be active against human infections caused by those bacteria," said lead author Christopher Goss, also of the University of Washington School of Medicine in Seattle.