Han, Aaron2022-02-072022-02-072021204-2021.99https://repository.mbru.ac.ae/handle/1/803Letter to Editor: Acinetobacter baumannii is a Gram-negative organism that has become a significant offender in health-care facilities, with the worldwide spread of carbapenem-resistant Acinetobacter baumannii (CRAB) significantly debilitating treatment options. Acquired carbapenemases of Ambler class D, or oxacillinases, namely OXA23-like, OXA-24-like, OXA-58-like, OXA-143-like and OXA-235-like groups, have been largely described in CRAB. Non-OXA carbapenemases are also acquired by A. baumannii, including metallo-β-lactamases of Ambler class B, such as the NDM-group, as well as Ambler class A carbapenemases, KPC and GES [1]. Intrinsically, two β-lactam hydrolysing enzyme groups occur in CRAB, OXA-51 and Acinetobacter-derived cephalosporinases (ADCs). While these two intrinsic enzyme categories secure weak carbapenem hydrolysis, acquisition of insertion sequence (IS) elements such as ISAba1 upstream of blaOXA-51 and blaADC may lead to enhanced expression, increasing resistance to cephalosporins, but only minimally to carbapenems. The existence of ISAba1 upstream of acquired blaOXA-23 enhances expression, resulting in higher carbapenem hydrolysis.enCarbapenem-resistant Acinetobacter baumanniiDubaiStudyOXA-23GES-11NDM-1Article