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Antimicrob. Agents Chemother. doi:10.1128/AAC.00709-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Inhibition of Gene Expression and Growth by Antisense Peptide Nucleic Acids in a Multiresistant -Lactamase-producing Klebsiella pneumoniae

Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2,Singapore, 117597; Department of Laboratory medicine, National University Hospital, Kent Ridge, Singapore, 119074

^* To whom correspondence should be addressed. Email: micpohcl{at}nus.edu.sg.

	Abstract

Klebsiella pneumoniae causes common and severe hospital and community-acquired infections with a high incidence of multi-drug resistance. The emergence and spread of -lactamase producing K. pneumoniae strains highlight the need to develop new therapeutic strategies. In this study, we developed antisense peptide nucleic acids (PNAs) conjugated to the (KFF)₃K peptide and investigated whether they could mediate gene-specific antisense effects in K. pneumoniae. No outer membrane permeabilization was observed with antisense PNAs when used alone. Antisense peptide-PNAs targeted at two essential genes, gyrA and ompA, were found to be growth inhibitory at concentrations of 20 µM and 40 µM, respectively. Mismatched antisense peptide-PNAs with sequence variations of the gyrA and ompA genes when used as controls were not growth-inhibitory. Bactericidal effects exerted by peptide-anti-gyrA PNA and peptide-anti-ompA PNA on cells were observed within 6 hours of treatment. The antisense peptide-PNAs specifically inhibited expression of DNA gyrase subunit A and OmpA from the respective targeted genes in a dose-dependent manner. Both antisense peptide-PNAs cured IMR90 cell cultures that were infected with K. pneumoniae (10⁴ CFU) in a dose-dependent manner without any noticeable toxicity to the human cells.