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. 2018 Jan 17;13(1):e0191522.
doi: 10.1371/journal.pone.0191522. eCollection 2018.

In Vitro activity of novel glycopolymer against clinical isolates of multidrug-resistant Staphylococcus aureus

Vidya P Narayanaswamy  1 , Scott A Giatpaiboon  1 , John Uhrig  2 , Paul Orwin  3 , William Wiesmann  1 , Shenda M Baker  1 , Stacy M Townsend  1
Affiliations

In Vitro activity of novel glycopolymer against clinical isolates of multidrug-resistant Staphylococcus aureus

Vidya P Narayanaswamy et al. PLoS One. .

Abstract

The incidence of multidrug-resistant (MDR) organisms, including methicillin-resistant Staphylococcus aureus (MRSA), is a serious threat to public health. Progress in developing new therapeutics is being outpaced by antibiotic resistance development, and alternative agents that rapidly permeabilize bacteria hold tremendous potential for treating MDR infections. A new class of glycopolymers includes polycationic poly-N (acetyl, arginyl) glucosamine (PAAG) is under development as an alternative to traditional antibiotic strategies to treat MRSA infections. This study demonstrates the antibacterial activity of PAAG against clinical isolates of methicillin and mupirocin-resistant Staphylococcus aureus. Multidrug-resistant S. aureus was rapidly killed by PAAG, which completely eradicated 88% (15/17) of all tested strains (6-log reduction in CFU) in ≤ 12-hours at doses that are non-toxic to mammalian cells. PAAG also sensitized all the clinical MRSA strains (17/17) to oxacillin as demonstrated by the observed reduction in the oxacillin MIC to below the antibiotic resistance breakpoint. The effect of PAAG and standard antibiotics including vancomycin, oxacillin, mupirocin and bacitracin on MRSA permeability was studied by measuring propidium iodide (PI) uptake by bacterial cells. Antimicrobial resistance studies showed that S. aureus developed resistance to PAAG at a rate slower than to mupirocin but similar to bacitracin. PAAG was observed to resensitize drug-resistant S. aureus strains sampled from passage 13 and 20 of the multi-passage resistance study, reducing MICs of mupirocin and bacitracin below their clinical sensitivity breakpoints. This class of bacterial permeabilizing glycopolymers may provide a new tool in the battle against multidrug-resistant bacteria.

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Conflict of interest statement

Competing Interests: I have read the journal's policy and the authors of this manuscripts have the following competing interests: VPN, SG, SMT, SMB and WPW are paid employees of Synedgen, SMT, SMB and WPW have ownership and patents affiliated with Synedgen, and SMB and WPW are Board members. The glycopolymer used in this study is protected by US Patent number 8,119,780 B2 and others pending in development of drug products to treat lung infections and related indications. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Bactericidal activity of PAAG against seventeen MRSA clinical isolates.
PAAG at a concentration of 100 μg/mL was added at timepoint 0 and monitored until 24h. Six log reductions in CFU/mL were observed in 58% of the MRSA isolates tested in 1-4h of treatment. 88% of the MRSA strains was observed within 12h of PAAG treatment. Data is presented as mean ± SD (n = 3).
Fig 2
Fig 2
(A-F). The relative fluorescence units (RFU) measured reflects PI intercalation into bacterial DNA by 2-1A (A), 2-4C (B), 2-5A (C), 2-9A (D), SA10 (E), PI alone and PI with PAAG (F) over 200 minutes, with the addition of control, 50–200 μg/mL PAAG, 100 μg/mL of vancomycin, oxacillin, mupirocin or bacitracin respectively.
Fig 3
Fig 3. In vitro resistance development study.
Development of in vitro resistance to PAAG was compared to that of two other topical antibiotics, mupirocin and bacitracin, plotted as MIC fold change vs passage number (A). S. aureus ATCC# 6538 developed resistance to PAAG and bacitracin at a slower rate compared to the rapid onset of resistance to mupirocin. Fig 3B is an expansion of Fig 3A showing the MIC fold change to PAAG and Bacitracin.
See this image and copyright information in PMC

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Grants and funding

The funders, through Synedgen Inc., provided support in the form of salaries for authors SMT, VPN, SG, SMB, and WPW, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the 'author contributions' section.