Study of <i>OmpK</i>35 and <i>OmpK</i>36 Expression in Carbapenem Resistant ESBL Producing Clinical Isolates of <i>Klebsiella pneumoniae</i>

Abstract

Background: Carbapenem resistant extended spectrum β-lactamase (ESBL) producing Klebsiella pneumoniae (K. pneumoniae) is increasing worldwide. Carbapenem resistance (CR) has been attributed not only to production of carbapenemases but also to permeability barriers due to outer membrane proteins (OmpK35 and OmpK36) disruption. Objective: Phenotypic detection of CR among ESBL producing K. pneumoniae isolates, followed by the evaluation of the role of ompK35 and ompK36 gene expression among carbapenem resistant K. pneumoniae (CR-KP) isolates. Methods: 100 ESBL producing K. pneumoniae isolates were included in this study. Minimum inhibitory concentration (MIC) of imipenem was performed for all isolates by broth microdilution method. For CR-KP isolates, phenotypic detection of K. pneumoniae carbapenemase (KPC), metallo-β-lactamase (MBL) and AmpC enzymes was performed followed by Realtime qRT-PCR to detect and quantify ompK35 and ompK36 gene expression. Results: 42% of our isolates were carbapenem resistant, and all of them were KPC producers either singly or in combination with MBL and/or AmpC production. Reduced expression of both ompK35 and ompK36 was detected in (52.38%) of CR-KP isolates, while reduced expression of ompK36 or ompK35 alone was found in (2.38%) and (33.33%) respectively. Twenty of 42 CR-KP isolates (47.62%), showing reduced ompK35 and ompK36 expression, exhibited high level resistance (HLR) (>32 µg/ml) to imipenem. There was a significant correlation between reduced expression of ompK36 and increase MIC values (p < 0.05). The combined production of MBL or AmpC together with reduced expression of ompK35 and/or ompK36 resulted in significant increase in imipenem MIC (p < 0.05). Conclusion: The combined OmpK35/OmpK36 loss resulted in HLR. However OmpK36 seems to play a major role in those strains. Imipenem MIC was markedly increased among K. pneumoniae showing carbapenemase and/or AmpC production together with loss of OmpK35 and/or OmpK36. A. A. M. N. El Din et al. 663 KeywordsOmpK35, OmpK36, K. pneumoniae, Carbapenem Resistant

Rectal carriage of carbapenem-resistant enterobacteriaceae: A menace to highly vulnerable patients

“…However, the nine strains observed resistant by ertapenem disk but negative or indeterminate by Carba-NP test may be due to the presence of different carbapenemase gene or due to the presence of noncarbapenemase mechanisms such as loss of porin channels, mutation of the efflux pumps, or ampC production. [1516] As per the CLSI 2016, sensitivity and specificity of Carba-NP test vary with the presence of different carbapenemase gene. The sensitivity was observed to be >90% in KPC, NDM-1, IMP, VIM SME, and SMS carbapenemase.…”