Drug combinations may be better than sum of their parts
The emergence of drug-resistant strains of bacteria is a growing problem worldwide. It is attributed to several factors, including what many scientists consider an overuse of antibiotics, allowing bacteria that survive antibiotic treatments to "learn" from the attacks. Now, researchers at Harvard Medical School have found that the resistance that makes such strains difficult to treat could potentially be exploited to make the bacteria more vulnerable. In a study using the common bacteria E. coli, researchers found that a combination of the two antibiotics doxycycline and ciprofloxacin completely halted the growth of doxycycline-resistant E. coli. Co-author Remy Chait explained that although doxycycline normally interacts with ciprofloxacin, making it less effective against the bacteria, the resistant strain of E. coli essentially "ignores" the doxycyline, leaving the ciprofloxacin free to attack the bacteria. The surprising result could have wide implications, although the study's lead author, Roy Kishony, cautioned in an e-mail that much additional work must be done before such treatments could be available for patients.
BOTTOM LINE: Using antibiotics in combination may work to overcome the resistance some bacteria have developed to the medications.
CAUTIONS: The study was done in a controlled laboratory environment, and additional research will be required before therapeutic experiments can be done.
WHAT'S NEXT: The researchers plan to look for drug combinations that are effective against more than one resistant strain of bacteria.
WHERE TO FIND IT: Nature, April 5.
Parasite brainwashes mice with a suicidal love for cats
The microscopic parasite Toxoplasma gondii lives in cats and mice. It can jump to humans as well, which is why pregnant women are advised not to empty litter boxes. Toxo has a two-stage life cycle. It grows to maturity inside mice, but it can only reproduce inside a cat's intestinal tract. From the parasite's perspective, the trick is making sure the cat eats the mouse. Researchers at Oxford discovered a few years ago that mice with Toxo are less afraid of cats. Now, a team at Stanford University headed by postdoctoral researcher Ajai Vyas has discovered why: Toxo eliminates the mouse's instinctive fear for the smell of cat urine. But the Stanford researchers found that the process went still further -- transforming fear into active attraction. "It wouldn't be totally unbelievable if all it did was destroy the behavior, the aversion," said Robert Sapolsky, one of the study's authors. "But what it does, it creates a new behavior instead." The parasite preferentially targets the amygdala, the part of the brain that generates fear, and it reprograms the mice with remarkably few side effects. The effect applies only to cat urine and not other animals. The mice have normal levels of general anxiety and normal reactions to other instinctive fears, such as bright lights, Sapolsky said.
BOTTOM LINE: A parasite can manipulate its host's behavior in order to ensure the parasite's survival.
CAUTIONS: The parasite knows how to zap a phobia, but the tactic doesn't exactly hold imminent promise for therapeutic application.
WHAT'S NEXT: Now that they know what Toxo does, the next step is figuring out how.
WHERE TO FIND IT: Proceedings of the National Academy of Sciences, April 2.
(Correction: Because of a reporting error, an item in yesterday's Discoveries column in the Health & Science section gave an incorrect first name for Dr. Roy Kishony of Harvard Medical School.)