MRGN: new classification for multidrug-resistant Gram-negative bacteria

New recommendations for infection control in the case of infection or colonization by multidrug-resistant Gram-negative bacteria were published by the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch-Institute, Germany. In this context, a new definition for multidrug-resistance, the so-called MRGN classification, was introduced. This was necessary because previous definitions did not seem suitable for the purpose of hospital hygiene. The MRGN classification grades multidrug-resistance by severity distinguishing 3MRGN and 4MRGN, resulting in different recommendations for infection control. In addition, not all antibiotics are regarded equally important in the classification, but only most relevant classes, such as ureidopenicillins, extended-spectrum cephalosporins, carbapenems, and fluoroquinolones, are taken into account. The MRGN classification is mainly based on resistance categories, not on resistance mechanisms. An exception has been made for carbapenemase-producing Enterobacteriaceae, which are always classified as 4MRGN irrespective of their antibiogram due to their importance. The correct MRGN classification should only be performed by experienced microbiological laboratories and requires a reliable detection of carbapenemases.