Background: Quercus infectoria gall extract is known to have broad spectrum antimicrobial
activity
in vitro. This study was conducted to determine the anti-microbial activity of
Q. infectoria gall extract against pathogenic
Leptospira and to evaluate the morphological changes
of extract-treated cells using a scanning electron microscope (SEM).
Methods: A two-fold serial microdilution broth assay was used to determine the minimum
inhibitory concentration (MIC) of aqueous
Q. infectoria gall extract against the
L. interrogans
serovar Javanica and the
L. interrogans serovar Icterohaemorrhagiae, at concentrations ranging
from 4.00 mg/mL to 0.0078 mg/mL. The minimum bactericidal concentration (MBC) was
determined by sub-culturing the broth from the microtiter plate wells that showed no apparent
growth or turbidity to the freshly prepared Ellinghausen-McCullough-Johnson-Harris (EMJH)
broth media, and it was subsequently observed under a dark field microscope following three
weeks of incubation for purposes of growth detection. The cell morphology of both extract-treated
and untreated
L. interrogans serovar Icterohaemorhagiae was analysed using the SEM.
Results: The results of the broth microdilution assay demonstrate that the aqueous
Q. infectoria gall extract possesses anti-microbial activity against both of the
L. interrogans
serovars with MIC values of 0.125 mg/mL. The MBC values for the
L. interrogans serovar
Javanica and the
L. interrogans serovar Icterohaemorhagiae are 0.125 mg/mL and 0.250 mg/mL,
respectively. The SEM micrograph shows changes in shape and size of the extract-treated cells
(at 8× MIC) in comparison to the untreated cells.
Conclusion: The
Q. infectoria gall extract displays anti-microbial inhibition and killing
activity against the pathogenic
Leptospira isolates, and thus has the potential for further
exploration of its efficacy and use in the treatment of leptospirosis.
