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Antibacterials thwart antibiotics
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THIS WEEK Mystery of 2km Antarctic ice circle solved
Antibacterials thwart antibiotics Bob Holmes
antibiotics, Petra Levin and Corey Westfall, at Washington University in St Louis, Missouri, exposed Escherichia coli to common antibiotics and triclosan, and measured their survival over 20 hours. When the bacteria were exposed to the antibiotics streptomycin or ciprofloxacin, plus triclosan, they were 10,000 times more likely to survive than those that weren’t also given triclosan. Further tests found that triclosan protects the MRSA superbug against vancomycin,
IF FIGHTING bacteria one way is good, two ways would be even better, you’d think. But not always: an antibacterial widely used in soaps and cleaning products actually helps microbes like MRSA beat powerful antibiotics. The substance in question is triclosan. It is not an antibiotic but a different type of compound that, rather than killing bacteria, stops them from growing instead. Triclosan is so widespread that there are concerns that “Triclosan protects the this may encourage bacteria to MRSA superbug against evolve resistance to it, posing a the last-resort antibiotic problem for hospitals that use treatment, vancomycin” antibacterials to prevent infections spreading. These concerns have helped prompt the a crucial antibiotic often used as US Food and Drug Administration a last resort in MRSA infections to ban the use of triclosan in (bioRxiv, DOI: 10.1101/090829). consumer hand soaps, and the We don’t know why triclosan FDA is pondering further has these effects, but one restrictions. explanation might lie in the Now there’s reason to worry different ways that antibiotics over even more serious effects. and antibacterials work. Most To see whether antibacterials antibiotics kill bacteria by can affect the performance of interfering with essential steps 8 | NewScientist | 17/24/31 December 2016
IT IS as mysterious as they come. A huge, 2-kilometre-wide circle spotted during a routine flight over an Antarctic ice shelf in 2014 has had scientists scratching their heads ever since. What could have caused it? Initially, they suspected a meteorite strike in 2004 had made the ice crater. But opinions changed when scientists first visited the circle on foot earlier this year. They found a 3-metre-deep depression with raised edges and, in –A helping hand for drug resistance?– the centre, three moulins – vertical well-like shafts in the ice – with two meltwater streams flowing into them. in their life cycle, such as These features point to the crater making cell walls. Since triclosan having once been a meltwater lake, prevents bacteria from growing, which subsequently drained into the they may not go through as ice shelf. It seems that strong winds many life cycle stages, becoming from the ice sheet’s interior are what impervious to antibiotics as a kicked off the process. These winds result. “A dormant cell has not erode the surface snow and bring in a lot of active targets, so there’s warmer air, which exposes the blue not much to corrupt,” says Kim ice underneath. This ice absorbs more Lewis at Northeastern University sunlight, boosting melt and forming a in Boston. large lake, which eventually collapsed We don’t yet know whether and drained to leave the telltale circle. triclosan could be aiding bacteria When the researchers drilled into to survive in the bodies of those the ice and ran radar tests further taking a course of antibiotics. west of the site, they found multiple Until we know more, it might be other lakes several metres under the wise for such people to cut their surface. This further supports the exposure to triclosan. idea that surface melting had taken The trouble is, it’s very hard to place and formed new lakes in the do that. “Triclosan is all over the region (Nature Climate Change, doi. place,” says Nathalie Balaban at org/bvr5). the Hebrew University of “We’ve shown that the East Jerusalem, Israel. “You’re giving Antarctic ice shelves are prone to local a treatment and you’re not even surface melting, which is important to aware it’s there.” take into account when looking at the Triclosan may have another future response of Antarctica to sinister effect. Antibiotic climate change,” says Stef Lhermitte treatment usually aims to kill all the bacteria causing an infection – at Delft University of Technology in the Netherlands. Surface melting can otherwise surviving microbes in theory destabilise the ice sheets. could pass on whichever genes “These researchers have really helped them resist the drugs. By enabling bacteria to persist in the dived in and shown us how winds can lead to melting and instability,” says presence of antibiotics, triclosan Ted Scambos at the National Snow may speed up their ability to and Ice Data Center in Boulder, evolve such resistance. If so, that Colorado. “But the East Antarctic ice could be a good argument for sheet is unlikely to break up anytime further restrictions on its use, soon.” Jane Palmer n Lewis says. n
THIS WEEK Mystery of 2km Antarctic ice circle solved
Antibacterials thwart antibiotics Bob Holmes
antibiotics, Petra Levin and Corey Westfall, at Washington University in St Louis, Missouri, exposed Escherichia coli to common antibiotics and triclosan, and measured their survival over 20 hours. When the bacteria were exposed to the antibiotics streptomycin or ciprofloxacin, plus triclosan, they were 10,000 times more likely to survive than those that weren’t also given triclosan. Further tests found that triclosan protects the MRSA superbug against vancomycin,
IF FIGHTING bacteria one way is good, two ways would be even better, you’d think. But not always: an antibacterial widely used in soaps and cleaning products actually helps microbes like MRSA beat powerful antibiotics. The substance in question is triclosan. It is not an antibiotic but a different type of compound that, rather than killing bacteria, stops them from growing instead. Triclosan is so widespread that there are concerns that “Triclosan protects the this may encourage bacteria to MRSA superbug against evolve resistance to it, posing a the last-resort antibiotic problem for hospitals that use treatment, vancomycin” antibacterials to prevent infections spreading. These concerns have helped prompt the a crucial antibiotic often used as US Food and Drug Administration a last resort in MRSA infections to ban the use of triclosan in (bioRxiv, DOI: 10.1101/090829). consumer hand soaps, and the We don’t know why triclosan FDA is pondering further has these effects, but one restrictions. explanation might lie in the Now there’s reason to worry different ways that antibiotics over even more serious effects. and antibacterials work. Most To see whether antibacterials antibiotics kill bacteria by can affect the performance of interfering with essential steps 8 | NewScientist | 17/24/31 December 2016
IT IS as mysterious as they come. A huge, 2-kilometre-wide circle spotted during a routine flight over an Antarctic ice shelf in 2014 has had scientists scratching their heads ever since. What could have caused it? Initially, they suspected a meteorite strike in 2004 had made the ice crater. But opinions changed when scientists first visited the circle on foot earlier this year. They found a 3-metre-deep depression with raised edges and, in –A helping hand for drug resistance?– the centre, three moulins – vertical well-like shafts in the ice – with two meltwater streams flowing into them. in their life cycle, such as These features point to the crater making cell walls. Since triclosan having once been a meltwater lake, prevents bacteria from growing, which subsequently drained into the they may not go through as ice shelf. It seems that strong winds many life cycle stages, becoming from the ice sheet’s interior are what impervious to antibiotics as a kicked off the process. These winds result. “A dormant cell has not erode the surface snow and bring in a lot of active targets, so there’s warmer air, which exposes the blue not much to corrupt,” says Kim ice underneath. This ice absorbs more Lewis at Northeastern University sunlight, boosting melt and forming a in Boston. large lake, which eventually collapsed We don’t yet know whether and drained to leave the telltale circle. triclosan could be aiding bacteria When the researchers drilled into to survive in the bodies of those the ice and ran radar tests further taking a course of antibiotics. west of the site, they found multiple Until we know more, it might be other lakes several metres under the wise for such people to cut their surface. This further supports the exposure to triclosan. idea that surface melting had taken The trouble is, it’s very hard to place and formed new lakes in the do that. “Triclosan is all over the region (Nature Climate Change, doi. place,” says Nathalie Balaban at org/bvr5). the Hebrew University of “We’ve shown that the East Jerusalem, Israel. “You’re giving Antarctic ice shelves are prone to local a treatment and you’re not even surface melting, which is important to aware it’s there.” take into account when looking at the Triclosan may have another future response of Antarctica to sinister effect. Antibiotic climate change,” says Stef Lhermitte treatment usually aims to kill all the bacteria causing an infection – at Delft University of Technology in the Netherlands. Surface melting can otherwise surviving microbes in theory destabilise the ice sheets. could pass on whichever genes “These researchers have really helped them resist the drugs. By enabling bacteria to persist in the dived in and shown us how winds can lead to melting and instability,” says presence of antibiotics, triclosan Ted Scambos at the National Snow may speed up their ability to and Ice Data Center in Boulder, evolve such resistance. If so, that Colorado. “But the East Antarctic ice could be a good argument for sheet is unlikely to break up anytime further restrictions on its use, soon.” Jane Palmer n Lewis says. n