The antibiotics-resistant superbug that emerged in South Asia appears to have claimed its first life. According to doctors who treated a man in Belgium, he went to a hospital in Pakistan after a car accident, and there he picked up the bacterial infection. While the man died back in June, his doctors announced today that he carried the superbug.
This new health scare intensified this week after researchers published a study in The Lancet Infectious Diseases characterizing “a new antibiotic resistance mechanism” in the U.K., India, and Pakistan. How bad is this “mechanism?”
The problem isn’t a particular kind of bacteria. It’s a gene that encodes an enyzme called New Delhi metallo-lactamase-1 (NDM-1). Bacteria that carry it aren’t bothered by traditional antibiotics, or even the drugs known as carbapenems deployed against antibiotic-resistant microbes.
The NDM-1 gene is a special worry because it is found in plasmids — DNA structures that can easily be copied and then transferred promiscuously among different types of bacteria. These include Escherichia coli, the commonest cause of urinary tract infections, and Klebsiella pneumoniae, which causes lung and wound infections and is generated mainly in hospitals [AFP].
It’s no worse than what we had before:
One might think that identical-twin bacteria—clones of each other—would grow up and live very similarly. But a study published today in Science that examined individual bacterial cells in detail found that genetically identical E. Coli cells actually seem to express their genes quite differently, simply because of the random accidents of how their molecular machinery happens to operate.
“The paper is quite rich,” said Sanjay Tyagi, a molecular biologist at New Jersey Medical School who was not involved in the research [but published a perspectives piece on it]. “People think that if an organism has a particular genotype, it determines its phenotype [observable characteristics]–that there’s a one-to-one relationship,” said Tyagi. “But as it turns out, [differences in gene expression] can arise just from chance.” [The Scientist]
Most of us associate the bacteria E. coli with nasty stomach ailments. But a new study published in Nature magazine suggests E. coli can not just turn stomachs, but could potentially turn the wheels of your car, since a genetically engineered strain of the bacteria has produced clean, road-ready biodiesel.
The bacteria can work on any type of biomass, including wood chip, switchgrass, and the plant parts that are left behind after a harvest–all contain cellulose, a structural material that comprises much of a plant’s mass. Study coauthor Jay Keasling and his colleagues report engineering E. coli bacteria to synthesize and excrete the enzyme hemicellulase, which breaks down cellulose into sugars. The bacteria can then convert those sugars into a variety of chemicals–diesel fuel among them. The final products are excreted by the bacteria and then float to the top of the fermentation vat before being siphoned off [Technology Review].
Eating red meat could make your body more vulnerable to a dangerous bacterial toxin, according to a new study. A sugar molecule, Neu5Gc, found in beef, lamb, pork, and unpasteurized milk can attach itself to the cells lining the human intestines and act as a magnet for toxins produced by certain strains of E. coli, often carried in the same meats. The result is bloody diarrhea and sometimes death. “This uncovered the first example of bacterium causing disease in humans by targeting a molecule which is incorporated into our bodies through what we eat,” [ABC Science] says researcher Travis Beddoe.
The study, published in Nature [subscription required], was conducted in petri dishes using mouse tissues and human cells. The scientists tested human gut and kidney cells steeped in these sugar molecules and discovered that the toxin was about seven times more likely to bind to these cells if the sugar was present. It is still “not clear how to extrapolate this precisely to the human body,” [Science News] says co-author Ajit Varki. That is, researchers don’t know exactly what it means for human health yet. Read More
A “sustainable chemical” company called Genomatica has developed a way to use sugar and genetically engineered bacteria to produce a common industrial chemical that’s usually produced using petroleum, and which is found in everything from Spandex to car bumpers. By using sugar from sugar cane as a feedstock, industrial chemical companies can get a cheaper alternative to petroleum-derived chemicals, while investing in processes that are less polluting and nontoxic, said Genomatica CEO Chris Gann [CNET].
Genomatica produces the chemical, 1,4-butanediol (BDO), by feeding pure glucose derived from sugarcane to E. coli bacteria, which has been engineered to produce BDO. “We have engineered the organism such that it has to secrete that product in order for it to grow,” says [company president] Christophe Schilling…. “The interests of the organism are aligned with our interests: It grows faster when it produces more” [Scientific American].
Villagers living deep in the Guyanese rain forest have developed resistance to an antibiotic they’ve never taken, and a malaria drug may be to blame. Researchers say the malaria drug is chemically similar to a type of widely used antibiotic, and they believe that the E. coli bacteria in the villagers’ guts evolved a broad resistance to both medications.
Antibiotic resistance is a major problem in Western countries, where strains of disease-causing bacteria such as Staphylococcus have adapted to beat some of the most commonly-used drugs. However, for a resistant strain to develop, bacteria usually need to be exposed to the drug involved [BBC News]. In this case, researchers say that a cheap malaria medication called chloroquine is similar enough to the antibiotic ciprofloxacin to allow the E. coli to develop defenses to the unknown drug.