Abstract:
The production of carbapenemases by Gram negative bacterial pathogens has become a worldwide threat to successful antibiotic therapy. Carbapenem resistance has been increasingly reported in recent years, and given the paucity of reliable antimicrobials, focus has shifted towards early surveillance of carbapenemases in microbiology laboratories. Detection of carbapenemases is primarily based upon careful recognition of decreased in vitro susceptibility to carbapenems by measurement of their MIC values or inhibition zone diameters. This is followed by a set of conventional phenotypic methods of variable efficiencies, such as the modified Hodge test and culture-based tests utilizing carbapenemase inhibitors. Among these, boronic acid compounds are used to inhibit Ambler class A carbapenemases, and EDTA and dipicolinic acid are used to inhibit Ambler class B carbapenemases. While the detection of carbapenemase producers is possible using screening culture media, the identification of carbapenemase genes relies on molecular techniques. Polymerase chain reaction experiments allow the detection of well-known carbapenemase genes, and sequencing is essential to the identification of new genes. Innovative biochemical and spectrometric detection are being developed to complement the molecular methods and shorten processing times needed for detection of carbapenemase activity. These are promising options to become routinely applied for rapid detection of carbapenemase-producing organisms with high precision and are most useful for epidemiologic purposes. Molecular techniques are nevertheless expensive, time consuming, and require well-trained personnel. This review is a summary of the current state-of-art of carbapenemase detection methods, with a description of the advantages and limitations of each.