Journal of Medical Bacteriology 2013. 2(3-4):26-31.

Evaluation of Phenotypic Methods for Detection of Klebsiella Pneumoniae Carbapenemase-Producing K. Pneumoniae in Tehran
Leila Azimi, Abdolaziz Rastegar-Lari, Malihe Talebi, Amirmorteza Ebrahimzadeh-Namvar, Somayeh Soleymanzadeh-Moghadam


Background: One of the main mechanisms of resistance to carbapenems is potential of Klebsiella pneumoniae to produce K. pneumoniae Carbapenemase (KPC). KPC is an important type of carbapenemase, which can hydrolyze carbapenems and other beta-lactam antibiotics. Modified Hodge Test (MHT) and  use  of  boronic  acid  as  a  KPC  inhibitor  are  two  types  of  phenotypic methods, which are used for detection of carbanemase-producing bacteria. Specificity of these two phenotypic tests for identification of KPC was assessed in this study.
Methods:   Forty-four   K.   pneumoniae   strains   were   isolated   from  wound infections   of   burn   patients.   All   isolates   were   identified   with   specific biochemical tests. Carbapenem-resistant K. pneumoniae isolates were identified by disc diffusion method and analyzed with cut off-points of CLSI 2011 guideline.   For   detection   of   KPC-producing   strains,   carbapenem-resistant isolates were examined with two different phenotypic (i.e. MHT and Boronic acid) methods. Subsequently, strains with positive phenotypic methods were examined by PCR as a molecular method.
Results: Twenty-eight (64%) out of 44 isolates were resistant to carbapenem according  to  CLSI  breakpoints  and  16  (36%)  were  susceptible.  MHT  was positive in all of carbapenem-resistant isolates but none of them have had the synergism effect between meropenem and boronic acid. Also, all isolates were negative for presence of KPC genes on gel electrophoresis. According to results MHT has not enough specificity for detection of KPC.


Carbapenemase, Klebsiella pneumoniae, Polymerase Chain, Reaction

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