Detection of OXA-23, GES-11 and NDM-1 among carbapenem-resistant Acinetobacter baumannii in Dubai: A preliminary study
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Letter 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 . 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.