Evaluation of the in vitro antimicrobial activity of a Pheroid®- entrapped plant extract against human pathogens
Date
2019Author
Van Lingen, Bianca
Bezuidenhout, Jaco J.
Cloete, Theunis T.
Metadata
Show full item recordAbstract
This plant extract (PE) has proven activity against fungi affecting
crops in South Africa. However, there is currently insufficient data on
the activity of the PE against human pathogens. The general aim of
this study is to determine whether the PE has in vitro antimicrobial
properties against 11 human pathogens. Identification of compounds
or treatments, which could have possible antimicrobial activity, will
facilitate the development of novel treatments, such as a Pheroid®
PE delivery system, and contribute to the indigenous knowledge of
SA's plant. The PE was formulated and entrapped into the Pheroid®
drug delivery system, containing different concentrations of the oil
phase, i.e. 4%, 8%, 10%, 13% and 50%. The in vitro antimicrobial activity
of these test formulations were compared to the activity of the PE
and control formulation, i.e. Pheroid® without the PE, to determine if
Pheroid® technology influenced the PE's activity. The formulations
were subjected to accelerated stability testing (AST), after which the
minimum bactericidal/fungicidal concentration (MBC/MFC) was
determined at month 0, 1, 2, and 3. Improvements were made to
this method by adding resazurin to determine the minimum
inhibitory concentration (MIC) and MFC [1]. The formulations were
subjected to characterization by Malvern Mastersizer, Malvern
Nanosizer and confocal laser scanning microscopy (CLSM). The
particle size, obtained from Malvern Mastersizer, for test formulations (4% and 8%) stayed relatively constant, while test formulations
10%, 13% and Pro-Pheroid® increased in size. There was statistically
no difference in mean particle sizes for the control formulations. The
zeta potential, obtained from Malvern Nanosizer, for both test- and
control formulations generally decreased during the AST, resulting in
more stable formulations. In general, after AST, test formulation (8%,
10%, and 13%) and PE tested against C. albicans had a 50% decrease in
MFC, while the 4% test formulation's MFC stayed constant. All the
control formulations had a N 90% decrease in MFC. The PE was found
to have moderate activity against C. albicans, S. cerevisiae, and T. dermatis with a MIC of 1725 μg/mL, 54 μg/mL, and 108 μg/mL
respectively. The test formulations had a general MIC of 108 μg/mL,
54 μg/mL, and 27 μg/mL against C. albicans S. cerevisiae, and T.
dermatis respectively.
Discussion
Characterization showed that optimisation of the formulations
was possible and that most of the formulations were stable i.e. no
aggregation, flocculation or creaming was observed during AST. In
conclusion, the addition of Pheroid® increased the MIC in all cases,
however, did not seem to have an effect on the MFCs in general. This
excludes S. cerevisiae where the PE had no MFC on its own, but by
adding Pheroid® there were MFCs. Generally, adding the PE to
Pheroid® resulted in more stable vesicles
URI
http://hdl.handle.net/10394/33324https://www.sciencedirect.com/science/article/pii/S1056871919303260
https://doi.org/10.1016/j.vascn.2019.106608