Carbapenems are among the “antibiotics of last resort” and can fight infections for which other drugs have long lost their effectiveness. However, even carbapenem-resistant pathogenic strains have emerged over the last decades. To find out whether a pathogen contains carbapenem-cleaving enzymes, the carbapenemases, Chinese scientists have developed a simple and fast assay based on a fluorescent probe and optical detection. They introduce their approach in the journal Angewandte Chemie .