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The potential of a naturally-produced inhibitory substance (E226), which is produced by Staphylococcus epidermidis strain E226 and shows activity against epidemic MRSA15

Abstract number: P1247

Al-Mahrous M., Tagg J., Upton M.

Objectives: In recent years, there has been much focus on a promising class of bacteriocins known as lantibiotics. The most prominent representative of lantibiotics, nisin, has already a long history of use in the protection of foodstuffs. Lantibiotics have also been considered for application in humans; however, they have not yet been used in the setting of chemotherapy on the same scale as traditional antibiotics.

We here investigate the cationic peptide antibiotic (E226) as a future opportunity for treating staphylococcal infections.

Methods:

1Investigation of S. epidermidis strain E226 was performed using simultaneous and deferred-antagonism against MRSA

2Purification and/or concentration of free inhibitors in broth supernatants was carried out using ammonium sulphate precipitation, Sep-Pak® cartridge, Speed-Vac®, Cation-exchange; then C18 reverse-phase chromatography.

3MALDI TOF/TOF was used for mass analysis

4Electron microscopy was used for ultra-structure diagnosis of a range of MRSA indicators

5Biological activities were tested using spot-on-loan assay

Results: The biological activity of E226 is heat-stable and displaying specificity for the closely-related S. aureus.

The high ammonium sulphate saturation (geqslant R: gt-or-equal, slanted80%) needed for precipitating E226 suggests its small mass. The cationic-exchange chromatography (pH 5.2) and the late elution from C18 column suggest the cationic nature of E226. MALDI TOF/TOF showed 3 species and sized the mass in a window between 2000 and 2800Da (Figure 1). This suggests further purification using high resolution HPLC to eliminate, if any, unrelated species.

The Electron microscopy diagnosis reveals a clear damage in the cell wall.

Figure 1. [A] Isolation of the active fraction using HPLC; [B] Detection of peptide species of E226 using mass spectrometry. Resulting amino acids were detected on a time-of-flight (TOF) mass spectrometer with matrix-assisted-laser-desorption ionization (MALDI).

Conclusions:

1The biological activity of the highly-purified extract of the heat-stable small mass inhibitory agent E226, which shows specific inhibitory activity against Epidemic MRSA-15 and strains of MSSA, suggests its nature as a bacteriocin, possibly of Class-I.

2The cationic-exchange separation and late elution of E226 from C18 reverse-phase column suggest that it is a hydrophobic in nature.

3Based on the electron microscopy diagnosis, E226 shows obvious damage to the protective cell wall of the sensitive indicators. This postulates the binding of the hydrophobic E226 to the negatively-charged lipid-II in the cell-membrane resulting in its lysis.

4E226 could have potential as topical therapeutic agents for treating highly drug-resistant staphylococcal infections.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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