• How can the clinical laboratory detect carbapenemases, which are enzyme that can make bacteria resistant to some of the most potent or broad-spectrum antibiotics available? • What is the clinical significance of detecting such an enzyme? Does it affect the care of the patient? • Finally, what practical advice can we give to help labs decide which of the many available tests is the best one for them? The antibiotics we discuss are the “carbapenems,” such as imipenem and meropenem. These are among the broadest spectrum antibiotics available. Bacteria that are resistant to carbapenems were identified as “urgent threats” by the CDC in 2019. Some bacteria produce enzymes which destroy these antibiotics, and these enzymes are called “carbapenemases.” By producing a carbapenemase, bacteria become resistant to these antibiotics, making carbapenems useless for treatment of infections caused by such bacteria. I am joined by an expert guest to discuss detection of carbapenemases, Dr. Patricia Simner. Dr. Simner is an Associate Professor of Pathology at Johns Hopkins University and an Associate Director of in the Medical Microbiology laboratory there. She is also a newly-appointed editor of JCM. Dr. Simner wrote an outstanding review in JCM called “Phenotypic Detection of Carbapenemase-Producing Organisms from Clinical Isolates” in 2018. It’s a few years old, but I think it is still the best available overview of these tests. We also talk about one of her more recent articles.