Sniffer dogs are often seen in airports, but Cliff, the beagle from Amsterdam, is more at home in a hospital. Cliff has been trained to sniff out the bacteria clostridium difficile, which is highly infectious and can cause outbreaks of diarrhoea on the ward. Scientists at the VU University Medical Centre in Amsterdam studied how effective Cliff was, and found that he can sniff out Clostridium difficile infections in stool samples and even in the air surrounding patients in hospital with a very high degree of accuracy.