Detection of carbapenemase-producing Enterobacteriaceae in various scenarios and health settings

Detection of carbapenemase-producing Enterobacteriaceae (CPE) is an important task at microbiology laboratories in hospitals. As the prevalence of CPE is increasing worldwide, the implementation of phenotypically based screening as well as confirmatory procedures to detect CPE are important for microbiologists. In addition to detection of carbapenem hydrolysis, the inhibition of activity against a carbapenem in the presence of several inhibitor compounds specific to class A, B, or class C beta-lactamases is a useful method to confirm the presence of carbapenemases in bacterial isolates. There is also a proteomic approach that compares the MALDI-TOF spectrum generated by the intact carbapenem (non-hydrolyzed) with that obtained after hydrolysis of the beta-lactam ring by beta-lactamase to reveal the presence of carbapenemases in bacterial isolates. Proteomic methods will probably be more frequently implemented in laboratories in the near future. Finally, molecular methods to directly or indirectly detect the presence of a carbapenemase genes are increasingly being used in microbiology laboratories. One of the main advantages of these methods is their speed, and also that they can be used directly with the clinical sample without the need for an isolated bacterial colony. Multiplex PCR, real-time PCR, DNA microarrays and pyrosequencing are some examples of molecular-based tests. Their main disadvantage is their cost, although prices are going down as the range of services increases. Surveillance of carriers is also an important task for infection control purposes. In this case, commercially available chromogenic medium supplemented with low carbapenem concentrations has shown an excellent ability to detect CPE. Moreover, molecular methods to detect specific carbapenemase genes directly from rectal swabs, stools, or other colonization sources have had excellent results.