NEW YORK (AP) — When it comes to preventing the spread of germs, maybe the president is on to something with his fondness for fist bumps.The familiar knocking of knuckles spreads only one-twentieth the amount of bacteria that a handshake does, researchers report. That’s better than a high-five, which still passes along less than half the amount as a handshake.So fist bumps — popularized by Barack Obama and others — seem to be the wisest greeting, especially during cold and flu season, said researcher David Whitworth of Aberystwyth University in Wales.The importance of hand hygiene is nothing new in medicine. But the researchers realized that while a lot of research focused on hands getting germy from touching doorknobs and other surfaces, only a few studies had looked at handshakes.“And there are alternatives to handshakes.