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Antimicrobial Assay


The potential of plant-derived products or any other agents for uses as antiseptic, disinfectant or antibiotic can be assessed in vitro using microbial test organisms. Here we can broadly classify our interests into two; antibacterial and antifungal assays and search for antiprotozoal agents.

Antibacterial and antifungal tests
For routine assessment of preliminary antimicrobial screening, the DISC-DIFFUSION METHOD is highly recommended. Filter paper discs impregnated with variable concentrations of the test agents are placed on agar plates inoculated with  micro-organisms. If the test micro-organisms are susceptible to the  drug, they fail to grow around the filter paper disc (see photograph) where the chemicals could reach through diffusion. The zone of inhibition around the disc is dependent on the ability of the chemical in question to diffuse through agar medium, the thickness of the agar medium in the plate, the size of inoculums, time and temperature of incubations, etc. Thus a good knowledge and experience on this assay system is required to generate reproducible results using the disc-diffusion method.

Once the activity of the plant-derived product is established using the disc-diffusion  method, it is often necessary to record the activity of the substance through  experiments which are more quantifiable and reproducible. Here we use the Minimal Inhibitory Concentration (MIC) which shows the lowest concentration of the test substance that inhibit the growth of  bacterial (or other test  micro-organism) growth in vitro. The advantage of this method is that the result is believed to correlate with the concentration of the agent achievable in the blood. For this assay, we recommend the cheep macrotube dilution technique that can easily be adopted in any microbiology lab. There are a number of other techniques one could use to test antibacterial/antifungal activity. For example, TLC based plates may be used to quickly identify antimicrobial agents for both crude and purified samples. A microtitre-based miniaturisation of the assay can also be adopted depending on the need for the assay.
 

You may  contact the site owner for further details of antibacterial/antifungal  assays. The following    key references are also of interest:

See our  article on antiviral activity test: Álvarez, Á.L,  HABTEMARIAM, S,  Juan-Badaturuge,  M, Jackson, C, Parra, F. (2011).  In vitro anti HSV-1 and HSV-2 activity of Tanacetum vulgare extracts and isolated compounds: An approach to their mechanisms of action.  Phytotherapy Research. 25(2), 296-301.  Abstract
...See an overview of our Research on Tansy...

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Antiprotozoal activity test:
Click here to see our free full-text article on the subject.

List of Other Relevant Publications

Motlhanka, D.M.T., Houghton, P., HABTEMARIAM, S. (2008) Antimicrobial  activity of Clerodendrum uncinatum from Botswana. Bots. J. Agric.  App. Sci. 4(1), 70-75.

Motlhanka,  D.M.T., Miljkovic-Brake, A.,  Houghton. P.J., , HABTEMARIAM, S.,  Hylands, P.J.  (2005) Antibacterial and Cytotoxic principles of  Commiphora glandulosa stem bark resin. J. Pharm.  Pharmacol.  57(9), 7.

HABTEMARIAM, S. (2003). In vitro antileishmanial effects of antibacterial diterpenes from two Ethiopian Premna species: P. schimperi and P. oligotricha. BMC Pharmacology 2003, 3:6 (The full text article can be accessed at http://www.biomedcentral.com/bmcpharmacol/)

HABTEMARIAM, S., MacPherson, A.M. (2000). Cytotoxicity and antibacterial activity of ethanolic axtract from leaves of a herbal drug, Bonset (Eupatorium perfoliatum). Phytotherapy Res. 14, 575-577.

Habtemariam, S., Gray, A.I., and Waterman, P.G. (1993). A novel antibacterial sesquiterpene from Premna oligotricha J. Nat. Prod. 56, 140-143.

Habtemariam, S., Gray, A.I. and Waterman, P.G.(1992). Antibacterial diterpenes from the aerial parts of Premna oligotricha. Planta Med.  58, 109-110.

Habtemariam, S., Gray, A.I., Lavaud, C., Massiot, G., Skelton, B.W., Waterman, P.G. and White, A.H. (1991).  ent-12-Oxolabda-8,13(16)-dien-15-oic acid and  ent-8b,12a-epidioxy-12b-hydroxylabda-9(11),13-dien-15-oic acid g-lactone: Two new diterpenes from the aerial parts of  Premna oligotricha. J. Chem. Soc. Perkin Trans. I , 893-896.

Habtemariam, S., Gray, A.I., Halbert, G.W. and Waterman, P.G. (1990). A novel antibacterial diterpene from Premna schimperi.  Planta Med. 56, 187-189. 

.... and  our publications' page for more references.

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Dr Habtemariam BSc, MSc, PhD........FRSM, FRSC. .... With a Principal Lecturer post at Greenwich, Dr Habtemariam is a leader of the BSc Pharmaceutical Science programme and researches on bioassay & natural products-based drug development. ....More

 

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In addition to our fully equipped tissue culture facilities, we have  access to various state-of-the-art equipment including ICP-MS, LC-MS, MALDI-TOF-MS, FABS-MS, FTIR, Laser-Raman,  scanning  and transmission  electron microscopes, flow cytometer, NMR (270, 300 and 500MHz),  automated DNA sequencers, various HPLC systems,  capillary electrophersis and ABI PRCmate DNA synthetisers.

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