In hospitals, a nasty little bacterium called Clostridium difficile causes problems for patients--it's highly infectious and can cause diarrhea among people who are already sick. Diagnosing whether a patient has C. diff, as it's called, requires a stool sample, which can take days to analyze. So scientists at the VU University Medical Centre in Amsterdam trained a beagle named Cliff to sniff out the nasty bacterium. The craziest part? Cliff doesn't need to sniff stool samples--he can tell just by walking up to a patient as the patient lies in bed.