Detection of kpc-type Carbapenemases in Clinical Isolates of Acinetobacter baumannii

Background: Multidrug-resistant Acinetobacter baumannii is associated with life threatening nosocomial infections and hospital outbreaks. The organism is resistant to most commonly used antibiotics including carbapenems. Aim and Objectives: To study carbapenemase production among multidrug-resistant clinical isolates of A. baumannii. Material and Methods: Fifty multidrug-resistant A. baumannii isolates were selected based on PCR identification of the bla gene. Minimum inhibitory OXA-51 concentrations were determined to imipenem and meropenem. Carbapenemase production was detected by the Modified Hodge Test (MHT) and the Combined Disc Method (CDM). Presence of the Klebsiella pneumoniae carbapenemases (KPC-2) type carbapenemase gene was shown by PCR using specific primers. Results: All isolates were resistant to imipenem and meropenem. MHT and CDM results showed carbapenemase production in 78% and 56% of the isolates, respectively. KPC-2 type gene was not observed in any of the isolates. Conclusion: No correlation was found between carbapenem susceptibility with phenotypic detection of carbapenemase production or KPC-type gene carriage. K e y w o r d s : A c i n e t o b a c t e r b a u m a n n i i , Carbapenemase, Modified Hodge Test, Combined Disc Method, KPC-2 Introduction: Acinetobacter baumannii is an important opportunistic pathogen associated with life Detection of kpc-type Carbapenemases in Clinical Isolates of Acinetobacter baumannii 1 1* Hannan Khodaei , Fereshteh Eftekhar Departement of Microbiology, Faculty of Biological Sciences and Technology, Shahid Beheshti University, G.C., Tehran, Iran threatening nosocomial infections and hospital outbreaks. The organism commonly targets critically ill patients in Intensive Care Units (ICU) and is resistant to most commonly used antibiotics including carbapenems [1]. A. baumannii is thought to be mostly due to the production of Ambler class A carbapenemases, class B metalloβ-lactamases and class D oxacillinases [2]. Klebsiella pneumoniae Carbapenemases (KPC) were initially identified in a K. pneumoniae isolate from the United States and were subsequently o b s e r v e d i n o t h e r m e m b e r s o f t h e Enterobacteriaceae worldwide [3]. KPC belong to Ambler class A, Bush subgroup 2f, serine-based beta-lactamases which are active against all betalactams, including the carbapenems. Twelve KPC variants (KPC-2 to KPC-11) are currently known. The KPC gene has been found associated with the plasmid-borne transposon Tn4401 [4]. Modified Hodge test (MHT) has been reported to be a good method for phenotypic detection of KCP in Enterobacteriaceae (CLSI, 2014). However, the test does not exclusively detect the KPC-type carbapenemases. Alternatively, a disc diffusion assay using a carbapenem as substrate and 3-aminophenyl boronic acid (combined disc method CDM) has been shown to reliably differentiae isolates producing KPC-type βJKIMSU, Vol. 6, No. 4, October-December 2017