Evaluation of the compatibility of phenotypic and molecular methods used to determine carbapenem resistance in enterobacterales isolates

Abstract

Aim: Carbapenems are one of the most important options for clinicians with few treatment options in the clinic due to their low side effects, rapid diffusion into tissues and use in all age groups. Therefore, it is important to be able to detect carbapenemase-producing isolates at an early stage for appropriate patient management and for infection prevention and control procedures. Antibiotic resistance genes and enzymes of microorganisms can be determined by phenotypic and molecular methods in clinical microbiology laboratories. Phenotypic methods are cheap, easy and easy to repeat but determination of resistance gene regions by molecular methods is costly, requires labour-experienced personnel and is time consuming. Determining whether the isolates possess the carbapenemase enzyme by phenotypic tests will provide convenience both for the patient and early initiation of the treatment and directing the clinician to the treatment. In this study, we aimed to evaluate the compatibility of phenotypic methods (carbapenemase inactivation method and Rapidec Carba NP) and molecular methods (Polymerase Chain Reaction) used to determine carbapenem resistance in Enterobacterales isolates. Material and Methods: Carbapenem resistant 60 and sensitive 20 Enterobacterales isolates were included in the study. E-test agar gradient diffusion, CIM, Rapidec Carba NP methods and PCR were studied. The agreement between the methods was determined by using the kappa (κ) coefficient with the cohen kappa analysis method.Results: In carbapenem resistant isolates, meropenem MİK50 and MİK90 determined as 32µg/ml, 64µg/ml, imipenem MİK50 and MİK90 determined as 32µg/ml, 128µg/ml, respectively. OXA-48 was positive in 54 (90%) isolates and NDM-1 in 6 (10%) isolates. The susceptibility of the isolates with OXA-48 carbapenemase gene region was 94.4% by CIM test and 92.6% by Rapidec Carba NP test, respectively. When the Kappa coefficient was evaluated, a very good agreement was observed between both tests and OXA-48. However, in the isolates with NDM-1 gene region, no compliance with CIM test was observed but Rapidec Carba NP test showed very good agreement. Conclusion: Rapid carbapenemase testing, such as Rapidec Carba NP and CIM, can play an important role in preventing the development of health-related outbreaks caused by carbapenemase-producing isolates, enabling faster prevention and control of infection.