Evaluation of Resistance Mechanisms in Carbapenem-Resistant .

Background: Carbapenem-resistant (CRE) is a major concern leading to morbidity and mortality in the world. CRE often is becoming a cause of therapeutic failure in both hospital and community-acquired infections.

Aim: This study aimed to investigate the resistance mechanisms of CRE by phenotypic and molecular methods.

Materials And Methods: Sixty CRE (50 , 6 , and 4 spp.) were isolated from October 2018 to June 2019. Antimicrobial susceptibility testing was carried out using phenotypic methods. The carbapenem resistance mechanisms including efflux pump hyperexpression, AmpC overproduction, carbapenemase genes, and deficiency in and were determined by phenotypic and molecular methods, respectively.

Results: Sixty CRE (50 , 6 , and 4 spp.) were isolated from October 2018 to June 2019. Amikacin was found to be the most effective drug against CRE isolates. All isolates were resistant to imipenem and meropenem by the micro-broth dilution. AmpC overproduction was observed in all spp. and three isolates. No efflux pump activity was found. Carba NP test and Modified Hodge Test could find carbapenemase in 59 (98%) isolates and 57 (95%) isolates, respectively. The most common carbapenemase gene was (72.8%) followed by (50.8%), (18.6%), (11.8%), and (6.7%). The and genes were not detected in 10 and 7 isolates, respectively.

Conclusion: The amikacin is considered as a very efficient antibiotic for the treatment of CRE isolates in our region. Carbapenemase production and overproduction of AmpC are the main carbapenem resistance mechanisms in CRE isolates. Finally, Carba NP test is a rapid and reliable test for early detection of carbapenemase-producing isolates.