New drugs could counter antibiotic resistant hospital infections

April 9th, 2009 - 5:36 pm ICT by IANS  

Washington, April 9 (IANS) Latest research findings that lack of sufficient phosphate in a bacterium could turn it into a killer could help develop new drugs to disarm the antibiotic resistant pathogens that cause serious hospital-acquired infections.
Pseudomonas aeruginosa, a bacteria that is a common cause of lung infections, also infests the intestinal tract of 20 percent of all Americans and 50 percent of hospitalised patients in the US.

It is one of the hundreds of bacteria that colonise the human intestinal tract, usually causing no apparent harm. It might even be beneficial to its host.

However, once the host is weakened by an illness, surgical procedure or immunosuppressive drugs, the bacteria can cause infection, inflammation, sepsis (pus-forming bacteria or their toxins in the blood or tissues) and death.

Why P. aeruginosa can suddenly turn on its host has eluded researchers - until now. Scientists have long known that after an operation or organ surgery, levels of inorganic phosphate fall.

The study authors, led by scientists of University of Chicago (U-C), hypothesised that phosphate depletion in the stressed intestinal tract signals P. aeruginosa to become lethal.

To test this theory, they let worms (Caenorhabditis elegans) feed on “lawns” of P. aeruginosa and Escherichia coli grown in both low-phosphate and high-phosphate media.

Only the worms that ate P. aeruginosa with low levels of phosphate died. The researchers dubbed the phenomenon “Red Death” since unexpected large red spots appeared on the worms before they died, according to an U-C release.

“These findings provide novel insight into the mechanisms by which P. aeruginosa is able to shift from indolent coloniser to a lethal pathogen when present in the intestinal tract of a stressed host,” said Alexander Zaborin, lead author of the study and a research professional at the U-C Department of Surgery.

“It is almost as if the bacterium sense when to strike,” said John Alverdy, study co-author and professor of surgery at the U-C Medical Center. “That should come as no surprise since the bacteria are smart, having been around for two billion years.”

The study will be published in the April 14 issue of the Proceedings of the National Academies of Science.

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