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antibiotics

Dirt

Caption: Researchers found a new class of antibiotics in a collection of about 2,000 soil samples.
Credit: Sean Brady, The Rockefeller University, New York City

Many of us think of soil as lifeless dirt. But, in fact, soil is teeming with a rich array of life: microbial life. And some of those tiny, dirt-dwelling microorganisms—bacteria that produce antibiotic compounds that are highly toxic to other bacteria—may provide us with valuable leads for developing the new drugs we so urgently need to fight antibiotic-resistant infections.

Recently, NIH-funded researchers discovered a new class of antibiotics, called malacidins, by analyzing the DNA of the bacteria living in more than 2,000 soil samples, including many sent by citizen scientists living all across the United States [1]. While more work is needed before malacidins can be tried in humans, the compounds successfully killed several types of multidrug-resistant bacteria in laboratory tests. Most impressive was the ability of malacadins to wipe out methicillin-resistant Staphylococcus aureus (MRSA) skin infections in rats. Often referred to as a “super bug,” MRSA threatens the lives of tens of thousands of Americans each year [2].

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Ice cream sundae

Thinkstock/piyaphat50

Most of us know how hard it is to resist the creamy sweetness of ice cream. But it might surprise you to learn that, over the past 15 years or so, some makers of ice cream and many other processed foods—from pasta to ground beef products—have changed their recipes to swap out some of the table sugar (sucrose) with a sweetening/texturizing ingredient called trehalose that depresses the freezing point of food. Both sucrose and trehalose are “disaccharides.” Though they have different chemical linkages, both get broken down into glucose in the body. Now, comes word that this switch may be an important piece of a major medical puzzle: why Clostridium difficile (C. diff) has emerged as a leading cause of hospital-acquired infections.

A new study in the journal Nature indicates that trehalose-laden food may have helped fuel the recent epidemic spread of C. diff., which is a microbe that can cause life-threatening gastrointestinal distress, especially in older patients getting antibiotics and antacid medicines [1, 2]. In laboratory experiments, an NIH-funded team found that the two strains of C. diff. most likely to make people sick possess an unusual ability to thrive on trehalose, even at very low levels. And that’s not all: a diet containing trehalose significantly increased the severity of symptoms in a mouse model of C. diff. infection.

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Ahmad Khalil

Ahmad (Mo) Khalil

The term “freeze-dried” may bring to mind those handy MREs (Meals Ready to Eat) consumed by legions of soldiers, astronauts, and outdoor adventurers. But if one young innovator has his way, a test that features freeze-dried biosensors may soon be a key ally in our nation’s ongoing campaign against the very serious threat of antibiotic-resistant bacterial infections.

Each year, antibiotic-resistant infections account for more than 23,000 deaths in the United States. To help tackle this challenge, Ahmad (Mo) Khalil, a researcher at Boston University, recently received an NIH Director’s New Innovator Award to develop a system that can more quickly determine whether a patient’s bacterial infection will respond best to antibiotic X or antibiotic Y—or, if the infection is actually viral rather than bacterial, no antibiotics are needed at all.

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Michael Fishbach

Michael Fishbach

Microbes that live in dirt often engage in their own deadly turf wars, producing a toxic mix of chemical compounds (also called “small molecules”) that can be a source of new antibiotics. When he started out in science more than a decade ago, Michael Fischbach studied these soil-dwelling microbes to look for genes involved in making these compounds.

Eventually, Fischbach, who is now at the University of California, San Francisco, came to a career-altering realization: maybe he didn’t need to dig in dirt! He hypothesized an even better way to improve human health might be found in the genes of the trillions of microorganisms that dwell in and on our bodies, known collectively as the human microbiome.

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Colony of Pseudomonas aeruginosa

Credit: Scott Chimileski and Roberto Kolter, Harvard Medical School, Boston

In nature, there is strength in numbers. Sometimes, those numbers also have their own unique beauty. That’s the story behind this image showing an intricate colony of millions of the single-celled bacterium Pseudomonas aeruginosa, a common culprit in the more than 700,000 hospital-acquired infections estimated to occur annually in the United States. [1]. The bacteria have self-organized into a sticky, mat-like colony called a biofilm, which allows them to cooperate with each other, adapt to changes in their environment, and ensure their survival.

In this image, the Pseudomonas biofilm has grown in a laboratory dish to about the size of a dime. Together, the millions of independent bacterial cells have created a tough extracellular matrix of secreted proteins, polysaccharide sugars, and even DNA that holds the biofilm together, stained in red. The darkened areas at the center come from the bacteria’s natural pigments.

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