Inhibiting the growth of methicillin-resistant Staphylococcus aureus in vitro with antisense peptide nucleic acid conjugates targeting the ftsZ gene

• One effective antisense oligonucleotide was obtained by computer prediction and dot-blot hybridization throughout the full length ftsZ gene of MRSA.
• Concentration- and time-dependent bacteriocidal antisense effects of anti-ftsZ PPNA against MRSA.
• The potency of the PPNA on bacterial growth and cell vitality is mediated by the down regulation or even knock-out of ftsZ expression.
• Specific inhibition of ftsZ gene transcript by PPNA.

SummaryBackgroundThe increasing emergence of clinical infections caused by methicillin-resistant Staphylococcus aureus (MRSA) challenges existing therapeutic options and highlights the need to develop novel treatment strategies. The ftsZ gene is essential to bacterial cell division.MethodsIn this study, two antisense peptide nucleic acids (PNAs) conjugated to a cell-penetrating peptide were used to inhibit the growth of MRSA. PPNA1, identified with computational prediction and dot-blot hybridization, is complementary to nucleotides 309–323 of the ftsZ mRNA. PPNA2 was designed to target the region that includes the translation initiation site and the ribosomal-binding site (Shine–Dalgarno sequence) of the ftsZ gene. Scrambled PPNA was constructed with mismatches to three bases within the antisense PPNA1 sequence.ResultsPPNA1 and PPNA2 caused concentration-dependent growth inhibition and had bactericidal effects. The minimal bactericidal concentrations of antisense PPNA1 and PPNA2 were 30 μmol/l and 40 μmol/l, respectively. The scrambled PPNA had no effect on bacterial growth, even at higher concentrations, confirming the sequence specificity of the probes. RT-PCR showed that the antisense PPNAs suppressed ftsZ mRNA expression in a dose-dependent manner.ConclusionOur results demonstrate that the potent effects of PNAs on bacterial growth and cell viability were mediated by the down-regulation or even knock-out of ftsZ gene expression. This highlights the utility of ftsZ as a promising target for the development of new antisense antibacterial agents to treat MRSA infections.