5 research outputs found
Antibacterial and anti-biofilm activities of Dicranopteris linearis leaf extracts
Biofilms are defined as cells that are irreversibly attached to a surface and embedded in an exopolysaccharide matrix. Biofilms can grow on living tissues and indwelling medical devices, which can threaten human health. Biofilms are more resistant to antibacterial agents and are difficult to eradicate. Moreover, the presence of non-multiplying cells in biofilms further complicates antibacterial treatments as they are able to tolerate extremely high doses of antibacterials. Staphylococcus aureus is one of the most frequent causes of biofilm-associated infections. Due to the various challenges in biofilm treatments, there is a need to search for effective compounds for biofilm treatments.<br> <br> Dicranopteris linearis or “resam” has been used in traditional medicine to treat fever, constipation and burns. The objective of this study was to determine the antibacterial and anti-biofilm activities of D. linearis against the non-multiplying cells and biofilms of S. aureus. Methanol crude extraction (MCE) and sequential solvent extraction (SSE) of D. linearis was conducted. The extracts were assessed for antibacterial and anti-biofilm activities.<br><br> Through broth microdilution assay, antibacterial activity
against <i>S. aureus </i>was observed for MCE of <i>D. linearis</i> leaves
(MCE(L)), MCE of <i>D. linearis</i> roots (MCE(R)) and methanol (MeOH) fraction
of SSE. The minimum inhibition concentration (MIC) and minimum bactericidal
concentration (MBC) for MCE(L) and MCE(R) were at 2.5 – 5.0 mg/ml while MeOH
fraction had MIC and MBC values at 5 mg/ml and 10 mg/ml, respectively.
Furthermore, time-kill assay against non-multiplying cells of <i>S. aureus </i>was
also conducted, by testing against <i>S. aureus</i> cultures that were growth
arrested through nutrient depletion, cold temperature and protein synthesis
inhibition. MCE(L) demonstrated bactericidal activity at 20 mg/ml against the
growth arrested cultures of <i>S. aureus</i> caused by nutrient depletion and
protein synthesis inhibition, and was not effective against culture growth
arrested at cold temperature.<br><br> For anti-biofilm activity, the water (H<sub>2</sub>O)
fraction and hexane (HEX) fraction was the most effective for biofilm
inhibition activity and biofilm disruption activity, respectively, when tested
against five <i>S. aureus</i> biofilm strains. The H<sub>2</sub>O fraction
demonstrated biofilm inhibition activity at 0.31 – 2.5 mg/ml while HEX fraction
showed biofilm disruption activity at 0.07 – 5 mg/ml. This is the first study
to report on the anti-biofilm activity of <i>D</i>. <i>linearis</i>. Both H<sub>2</sub>O
fraction and HEX fraction did not inhibit cell growth, thus the anti-biofilm
effect observed was only due to the biofilm structure itself or the genes that
codes for the biofilm.<br><br> Additionally, H<sub>2</sub>O fraction was able to inhibit <i>S.
aureus</i> biofilm formation on various polymer materials commonly used in
medical settings: polystyrene (85-93% inhibition), polyvinyl chloride (76-91%
inhibition), polyethylene (68-90% inhibition); polypropylene (52-93%
inhibition), silicone rubber (68-94% inhibition). The presence of various
phytochemicals such as flavonoids terpenoids, tannins, cardiac glycosides,
phenols, quinones and saponins were identified in H<sub>2</sub>O fraction.
However, further purification and isolation of H<sub>2</sub>O fraction was not
conducted due to difficulties in identifying the specific phytochemical
responsible for the biofilm inhibition effect.<br><br> HEX fraction was able to disrupt about 42-75% of <i>S. aureus</i>
biofilms. Through scanning electron microscopy, HEX fraction demonstrated
destruction of the biofilm structure and scant biofilms were observed, with
only few bacterial cells. Few phytochemicals were identified in HEX fraction,
and thus, HEX fraction was selected for further purification and isolation
process. Purification of HEX fraction had yielded Fraction A and based on
nuclear magnetic resonance spectroscopy and liquid chromatography-mass
spectrometry data, the compound from Fraction A was identified as
Alpha-tocopherol.<br><br> Alpha-tocopherol was
tested for anti-biofilm activity and was found to exhibit biofilm disruption
activity against <i>S.</i> <i>aureus</i> biofilms at 0.01 – 0.5 mg/ml.
Currently, there has not been any study reported on the biofilm disruption
effect of alpha-tocopherol. This will be the first study to report on the
biofilm disruption activity of alpha-tocopherol against <i>S. aureus</i>
biofilms or any other bacterial biofilms.<br><br> Further investigation revealed that alpha-tocopherol affects
the biofilm matrix and not the cells within biofilms. Alpha-tocopherol was also
effective in disrupting <i>E</i>. <i>faecalis</i> biofilm (23% disruption) and <i>E.
coli</i> biofilm (31% disruption), and the polymicrobial biofilms of <i>S.
aureus</i> + <i>E. faecalis</i> (22-25% disruption) at 0.01 – 0.5 mg/ml. The
combination of alpha-tocopherol with vancomycin had mostly showed indifferent
effect towards the disruption of biofilm biomass. The combination of
alpha-tocopherol and vancomycin was indifferent to the presence of each other
in reducing the biofilm biomass of <i>S. aureus</i> and would not cause a
greater effect in disrupting biofilm as compared to using either
alpha-tocopherol and vancomycin alone. Furthermore, the combination of
alpha-tocopherol and vancomycin at low concentrations (4 µg/ml of
alpha-tocopherol + 0.008 µg/ml of vancomycin) was shown to affect the viability
of cells within <i>S. aureus</i> biofilms.<br><br> In conclusion, findings from this study demonstrated the
antibacterial and anti-biofilm activities of <i>D. linearis</i>, with
alpha-tocopherol being the active constituent for biofilm disruption activity.
Further work on the biofilm disruption effect of alpha-tocopherol is necessary
to explore its potential use in anti-biofilm therapies
Bacterial pigments:The bioactivities and as an alternative for therapeutic applications
Synthetic pigments have been widely used in various applications since the 1980s. However, the hyperallergenicity or carcinogenicity effects of synthetic dyes have led to the increased research on natural pigments. Among the natural resources, bacterial pigments are a good alternative to synthetic pigments because of their significant properties. Bacterial pigments are also one of the emerging fields of research since it offers promising opportunities for different applications. Besides its use as safe coloring agents in the cosmetic and food industry, bacterial pigments also possess biological properties such as antimicrobial, antiviral, antioxidant and anticancer activities. This review article highlights the various types of bacterial pigments, the latest studies on the discovery of bacterial pigments and the therapeutic insights of these bacterial pigments which hopefully provides useful information, guidance and improvement in future study