Antistaphylococcal and antibiofilm activities of ethanolic extract of Piper cubeba L.
Staphylococcus aureus is a very adaptable foodborne pathogen responsible for food outbreaks and a source of cross contamination in fresh and processed foods worldwide. Methicillin-resistant S. aureus (MRSA) strains which were initially addressed in humans is being marked as emerging community acq...
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Format: | Thesis |
Language: | English |
Published: |
2018
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Online Access: | http://psasir.upm.edu.my/id/eprint/77092/1/FSTM%202018%2026%20IR.pdf |
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Summary: | Staphylococcus aureus is a very adaptable foodborne pathogen responsible for food
outbreaks and a source of cross contamination in fresh and processed foods
worldwide. Methicillin-resistant S. aureus (MRSA) strains which were initially
addressed in humans is being marked as emerging community acquired pathogen in
recent years. The resistance of staphylococci towards various novel and existing
antimicrobial agents has developed as a problem. Noticeably, the significance of
medicinal plants and traditional health practices has gained increasing attentions
principally in solving the impact of emergence, spread and resistance of
microorganisms of the world. Simultaneously, there is a concern in the field of food
safety, quality and preservation to counter the rising of resistant pathogens and the
limitation of synthetic chemical additives in the food system. Among the plants
investigated to date, one showing enormous potential is the pepper family otherwise
known as Piperaceae. Piper cubeba L. has infinite medicinal properties and practiced
to treat a number of diseases. In this study, the Piper cubeba L. extract was examined
for its antistaphylococcal and antibiofilm activity against Staphylococcus aureus
food isolates, S. aureus human isolates and a reference strain S. aureus ATCC6538P.
P. cubeba L. berries were extracted using ethanol, methanol and water as solvent.
The antimicrobial activity of ethanol, methanol and water extracts of P. cubeba L.
against S. aureus isolates in terms of disc diffusion was performed. Further,
minimum inhibitory concentration (MIC), minimum bactericidal concentration
(MBC) and time kill curve were performed using ethanol extract referring to
standard method of Clinical and Laboratory Standards Institute (CLSI). The
ethanolic P. cubeba L. extract was assessed for its stability at various temperature
and pH conditions relevant to food production and storage. Scanning electron
microscopy (SEM) was used to visualize the effect of ethanolic P. cubeba L. extract
on representative S. aureus. The bioactive compounds present in ethanolic P. cubeba
L. extract were determined using Gas Chromatography-Mass Spectrometry (GC-MS)
and Liquid Chromatography-Mass Spectrometry (LC-MS). Biofilm forming patterns
of S. aureus isolates and antibiofilm activity of ethanolic P. cubeba L. extract were
performed in presterilized flat-bottom 96-well microplate and were quantified using 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenyl-amino) carbonyl]-2H
tetrazolium-hydroxide (XTT) reduction assay. The effect of ethanolic P. cubeba L.
extract was assessed on cut-up parts of chicken (breast, wing and drumstick) as
natural sanitizer. Visual attribute sensory acceptability was evaluated on raw and
steamed chicken meat treated with ethanolic P. cubeba L. extract. Toxicity effect of
the extract was evaluated using the brine shrimp lethality assay. The results showed
that ethanol and methanol P. cubeba L. extract exhibited significant diameter of
inhibition zone in the range of 7.23 – 8.50 mm and 7.13 – 8.57 mm respectively,
against S. aureus isolates. MIC and MBC of ethanolic extract were in the range of
0.625 – 2.5 mg/ml and 1.25 – 5 mg/ml against all tested isolates, respectively. The
time-kill curve plots revealed S. aureus food isolates CM10 and CM14 were killed
within 1 h of incubation at a concentration of 4× MIC. As for S. aureus human
isolate and ATCC6538P the time-kill curve plot revealed bacteriostatic effect of the
P. cubeba L. extract. Trends of increasing, decreasing and constant MIC and MBC
values were observed upon heat treated ethanolic P. cubeba L. extract as compared
to non-heat treated extract. Generally, the pH altered extracts varied the MIC and
MBC values of the S. aureus isolates. Under SEM observation, the treated cells
underwent a significant transition from initially smooth surfaces cells to completely
distort and shrank cells. The major volatile bioactive compounds determined using
GC-MS were β-cubebene, cubebol, α-copaene, α-cubebene, caryophyllene and
germacrene-D. Non- volatile compounds identified by LC-MS were 5,7-dihydroxy-
3',4'-dimethoxy-6,8-dimethylflavone, brosimacutin B, phellodensin D, 9E,12Z,15Zoctadecatrienoic
acid, 2,4-dimethyl-tetradecanoic acid, eriodictyol 7,3'-dimethyl
ether 4'-prenyl ether, erioflorin methacrylate, 12-oxo-5E,8E,10Z-dodecatrienoic acid
and (S)-β-himachalene. S. aureus isolates exhibited strong adherent ability at 37°C
and 28°C while weak and non-adherent capability mostly observed at 7°C. The
biofilm formation of S. aurues can be inhibited by sessile minimal inhibitory
concentration (SMIC) of 6.25 – 25 mg/ml and the formed S. aurues biofilm can be
eradicated by minimal biofilm eradication concentration (MBEC) values of 25 – 50
mg/ml. In general, reduction 3 Log10 of S. aureus, total plate count, E. coli and
coliform was started to observe at ethanolic P. cubeba L. extract of 0.50% on the cutup
parts of chicken. P. cubeba L. sanitized raw and steamed chicken meat at 0.05%,
0.50% and 5.00% was accepted by the panelists. Brine shrimp lethality test exhibited
no significant toxicity (LC50 = 6.98 mg/ml) against brine shrimp naupili. In
conclusion, ethanolic P. cubeba L. extract with potential antimicrobial and
antibiofilm activities could be prominently marked as a valuable natural
antimicrobial, antibiofilm, and sanitizing agent in the food safety field. |
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