Penicillin facilitates the entry of antisense constructs into Streptococcus mutans

Authors

  • Felicity S.A. McLeod,

    1. Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
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  • Robin S. Simmonds

    Corresponding author
    1. Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
    • Correspondence: Robin S. Simmonds, Department of Microbiology and Immunology, University of Otago, P.O. Box 56, 9054 Dunedin, New Zealand. Tel.: +64 3 479 7478: fax; +64 3 479 8540; e-mail: robin.simmonds@otago.ac.nz

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Abstract

Antisense oligonucleotides (AS-ODN) target genes in a sequence-specific manner inhibit gene function and have potential use as antimicrobial agents. Cell barriers, such as peptidoglycan, cell surface proteins and lipopolysaccharide membranes, prevent delivery of AS-ODN into the bacterial cell, limiting their use as an effective treatment option. The β-lactam antibiotic penicillin was examined for its ability to deliver phosphorothioate oligodeoxyribonucleotides (PS-ODNs) and γ32 P-ODN into Streptococcus mutans OMZ175. Treatment of lag-phase S. mutans OMZ175 cells with penicillin and FBA (PS-ODN targeting the fructose-biphosphate aldolase gene), resulted in prolonged suppression of growth (> 24 h) and fba expression (656.9 ± 194.4-fold decrease at 5 h). Suppression of both cell growth and fba expression corresponded with a greater amount of γ32 P-ODN becoming cell associated, with a maximum γ32 P-ODN concentration per cell achieved 5 h after penicillin treatment (6.50 ± 1.39 × 108 molecules per CFU). This study confirms that for S. mutans OMZ175, the peptidoglycan layer acts as a major barrier preventing AS-ODN penetration and suggests that the use of agents such as penicillin that interfere with peptidoglycan integrity can significantly increase the uptake of PS-ODN by these cells.

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