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

Detection of OXA-23, GES-11 and NDM-1 among carbapenem-resistant Acinetobacter baumannii in Dubai: A preliminary study Sir, 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 OXA-23-like, OXA-24-like, OXA-58-like, OXA-143-like and OXA-235like 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 bla OXA-51 and bla ADC may lead to enhanced expression, increasing resistance to cephalosporins, but only minimally to carbapenems.The existence of ISAba1 upstream of acquired bla OXA-23 enhances expression, resulting in higher carbapenem hydrolysis [2].In Dubai, a major attraction spot hosting over 150 nationalities, there are no published data defining current mechanisms of resistance in CRAB.We highlight here the molecular epidemiology and genetic relatedness of CRAB isolates recovered from Dubai hospitals between 1 June 2015 and 1 June 2016.CRAB isolates were delivered to Microbiology Research Laboratories of Zayed University, Dubai, for archiving and antibiotic susceptibility testing, then to Microbiology Laboratory of Saint-Joseph University, Beirut, for further phenotypic and genotypic analysis.Antimicrobial susceptibility testing was performed for different antibiotic classes using a disk diffusion method, while for colistin and tigecycline, it was performed by broth microdilution according to CLSI 2017 criteria and FDA breakpoints for tigecycline.All isolates were screened by PCR sequencing for carbapenemase genes of Ambler group A (bla KPC and bla GES ), group B (bla IMP-1 , bla IMP- 2 , bla NDM-1 and bla VIM-2 ) and group D (bla oxa-23 , bla oxa-24 , bla oxa-58 ), as described previously [3].Isolates were screened for insertion sequence ISAba1.PCR mapping experiments using ISAba1 forward and OXA-23 reverse primers was done on bla oxa-23 -positive isolates.