1
4 | NewScientist | 25 February 2012 CONTRASTO/EYEVINE DOSING livestock with antibiotics can be bad for farmers’ health. A strain of MRSA that causes skin infections and sepsis in farm workers evolved its resistance to antibiotics inside farm animals. The ST398 strain of MRSA first appeared in 2003 and is prevalent in US livestock. Humans who pick it up from animals can become dangerously ill, but it cannot yet spread from human to human. A team led by Paul Keim of the Translational Genomics Research Institute in Phoenix, Arizona, sequenced the genomes of 88 closely related strains of Staphylococcus aureus, the bug that can become MRSA. Their findings suggest that ST398 was originally a harmless strain living in humans, which migrated into livestock where it acquired antibiotic resistance (mBio, in press). Superbug’s source For some time microbiologists have been concerned that giving large amounts of antibiotics to livestock can promote antibiotic resistance. Keim’s study provides a powerful example, says Ross Fitzgerald of the University of Edinburgh, UK. Earlier this year the US Food and Drug Administration announced new restrictions on using preventive antibiotics in livestock, but the rules cover a small subset of drugs constituting just 0.2 per cent of antibiotics used on farms. As a result they are not expected to do much good. Invasive ultrasound WOMEN seeking abortions in Virginia may soon have to undergo an invasive ultrasound scan first – a move supposedly designed to inform the women but which some claim aims to stigmatise them instead. If a new senate bill is passed in Virginia this week, ultrasound would be performed in order to “more accurately determine gestation age”. The women would then be offered the chance to see the image “to make an informed choice”. To get a clear image of the fetus in early pregnancy, ultrasound scans tend to be performed trans-vaginally – a procedure that involves inserting a probe into the vagina. Tracy Weitz at the University of California in San Francisco agrees that it is “critical to assess gestational age before an abortion”, but says that the bill assumes women don’t know what they’re doing. “Women are not choosing abortions because they do not know what is in their uterus but because of the conditions of their lives,” she says. Secret mind JOHN NASH’S mind is even more exquisite than we thought. The Nobel laureate, famous for both his work in game theory and his schizophrenia – as portrayed in the book and film A Beautiful Mind – had ideas about cryptography and complexity decades before their time. The revelations come in recently declassified letters exchanged between the US National Security Agency and Nash in 1955. In them, –Look for life underground– –Also keen on P vs NP– Atacama’s buried oasis IT’S the driest desert in the world, but Chile’s Atacama is far from lifeless. An oasis of microbes has been found 2 metres below its surface using an instrument that could one day hunt for life on Mars. Victor Parro of the Centre for Astrobiology in Madrid, Spain, and colleagues discovered the thriving community of bacteria, archaea, DNA, and other molecules associated with life. “This is a kind of oasis in the Atacama,” Parro says. The microbes, along with similar life forms found in the top 30 centimetres of the surface, survive thanks to thin films of water that form on salt crystals in the soil (Astrobiology, DOI: 10.1089/ ast.2011.0654). The water may have been pulled from the atmosphere, or from subsurface aquifers. “For these microbes, the most important thing is to get some water,” Parro says. The discovery was made using an instrument called SOLID (Signs of Life Detector), which searches for molecules associated with life – such as sugars and DNA – with the help of 300 antibodies that bind to the molecules. When the antibody finds its target molecule it grabs hold of it and a special camera photographs the linked pair. Pregnancy tests, which look for a hormone associated with the early stages of pregnancy, use a similar strategy. An instrument that would use the technique to hunt for fossilised life may fly on the European Space Agency’s ExoMars rover mission in 2018. WIN/GETTY UPFRONT “The bug was harmless until it migrated to livestock where it acquired antibiotic resistance”
