Antimicrobial activity of antisense peptide-peptide nucleic acid conjugates against non-typeable Haemophilus influenzae in planktonic and biofilm forms

Taketo Otsuka, Aimee L. Brauer, Charmaine Kirkham, Erin K. Sully, Melinda M. Pettigrew, Yong Kong, Bruce L. Geller, Timothy F. Murphy

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Background: Antisense peptide nucleic acids (PNAs) are synthetic polymers that mimic DNA/RNA and inhibit bacterial gene expression in a sequence-specific manner. Methods: To assess activity against non-typeable Haemophilus influenzae (NTHi), we designed six PNA-peptides that target acpP, encoding an acyl carrier protein. MICs and minimum biofilm eradication concentrations (MBECs) were determined. Resistant strains were selected by serial passages onmedia with a sub-MIC concentration of acpP-PNA. Results: The MICs of six acpP-PNA-peptides were 2.9-11 mg/L (0.63-2.5 mmol/L) for 20 clinical isolates, indicating susceptibility of planktonic NTHi. By contrast, MBECs were up to 179 mg/L (40 mmol/L). Compared with one original PNA-peptide (acpP-PNA1-3'N), an optimized PNA-peptide (acpP-PNA14-5'L) differs in PNA sequence and has a 5' membrane-penetrating peptide with a linker between the PNA and peptide. The optimized PNA-peptide had an MBEC ranging from 11 to 23 mg/L (2.5-5 mmol/L), indicating susceptibility. A resistant strain that was selected by the original acpP-PNA1-3'N had an SNP that introduced a stop codon in NTHI0044, which is predicted to encode an ATP-binding protein of a conserved ABC transporter. Deletion of NTHI0044 caused resistance to the original acpP-PNA1-3'N, but showed no effect on susceptibility to the optimized acpP-PNA14-5'L. The WT strain remained susceptible to the optimized PNA-peptide after 30 serial passages on media containing the optimized PNA-peptide. Conclusions: A PNA-peptide that targets acpP, has a 5' membrane-penetrating peptide and has a linker shows excellent activity against planktonic and biofilm NTHi and is associated with a low risk for induction of resistance.

Original languageEnglish (US)
Pages (from-to)137-144
Number of pages8
JournalJournal of Antimicrobial Chemotherapy
Volume72
Issue number1
DOIs
StatePublished - Jan 2017
Externally publishedYes

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© The Author 2016.

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