Microbiology Project Topics

In vitro Determination of Bactericidal Effect of Garlic on Staphylococcus Aureus

Invitro Determination of Bacteriocidal Effect of Garlic on Staphylococcus Aureus

In-Vitro Determination of Bactericidal Effect of Garlic on Staphylococcus Aureus

Chapter One


  1. To assess the bacteriocidal property of garlic as alternative to synthetic antibiotics
  2. To know the concentration of garlic extract that will be effective on the pathogen.



          Over the centuries, spices in the genum Allium have acquired reputation in the folklore of many cultures as formidable prophylactic and therapeutic medicinal agents.  Grlic has been in use for a long time and was found useful although the extent was not accurately recorded.

Grlic (Allium sativum) is a hardy perennial of Asiatic origin belonging to the plant order lilies and family liliaceae.  Europeans have grown it for more than two hundred (200) years with other countries like Italy, Mexico, and Tahiti.  It is grown for its pungent bulb segment sometimes called cloves, seeds are seldomly produced, cultural practice are similar to those of onions, though it belongs to the same genus with onions.  Harvest of the mature dry bulb is eight to nine (8-9)  months after planting.  California is the most important producing state.  Hill, (1971).  Garlic is of two varieties:  – the pink and the white garlic.  The popular varieties are:  the pink and white garlic:  the pink one which has a purgent flavour and many cloves, making it mostly difficult to prepare.  Another variety is the Tahit garlic which is white with strong flavour Kotschevar, (1989). Garlic is a very nutritious substance that contain high level of protein, vitamin A and C thiamine and trace mineral including copper, iron, zinc, tin, calcium, potassium, aluminium, sulphur, germinium and selenium.  Although garlic is not regarded as good source of these substances because of the quantity it contains, yet it is regarded as being nutritious.  Bolton (1982) It is cited in Egyptian cordex Ebers, a thirty five (35) century old document, as being useful in treatments.  However, garlic has a long history of use for medicinal purposes.  One of the earliest cultivated plant (Garlic) mentioned in the bible and in literatures of the ancient Heroes, Babylonians, Greek and Romans.  It is fed to the Roman soldiersa to make them strong.  It was part of the diet of the ancient pyramid builders of Egypt (Hayness, 1975),

Damrau and Mareovic attributed atleast some of the favourable effect of garlic administration in hypertension to it’s control of intestinal putrefaction and avoidance of toxin absorption.  The putrefaction hypothesis has recently been reconsidered as a result of work involving microbial ecology of gut (coates, 1981).

Several spices and herbes have been known to possess antimicrobial activities. Studies in the early part of this century described inhitories of volatile components of onion; garlic and other condiments and their effects on a variety of micro-organisms (Shelef 1980) have become sporadic with the wide spread use of modern preservation technique but a renewed interest in the antimicrobial activities of the spices and herbs may fulfill more than one function  in the foods they are added.

Spices and herbs are used in food mainly for their flavours and aroma.  Their  flavour component consist of such compounds as alcohol, aldehyde, esters, terpene, phenols, organic acid and others, which have not yet be fully identified.  In addition to importing flavour, certain spices prolong the storage life of foods by bacteriostatic and bacteriocidal activity.  Some prevent rancidity by their antiocidant activities and being national food stuffs they appeal to consumers who tends to question the safety of synthetic food additives (Shelef 1980).

The medicinal qualities of garlic have been described by Phing, the elder, Aristophanes, Hippocrates and Galen.  In phing’s history, Natural garlic was recommended for gastrointestinal disorder, dog and snake bites, scorpion stings, asthma, convulsion, tumours and constipation.  Hippocrates  recommended garlic use as a laxative, divertic and for uterine tumour.  Additionally, garlic has been purpoted to be of healing value in such condition as hypertensions, arthritis, cancer leprosy, heavy emtal poising, dysentery even athlete’s foot and dandruff.

Garlic has been used against arthritis, most often by simply ribbing the affect part of garlic is commonly used against hypertension.  Garlic juice in water is used as an antiseptics.  Garlic has been used externally in ointment forms to treat ring worm.

A solution of boiled cloves with vinegar and sugar time was popular for treatment of asthma (Bolton, 1982)

Spillar, (1980) suggested a name for those components of food we use in higher concentration than normally present in our food and do exercise an effect that cannot be properly called physiological or nutritional effect but an effect resembling pharmacological effect.  The therefore, suggested nutritional effect but an effect resembling pharmacological effect.  He therefore, suggested nutritional  pharmacology for such field. He defined nutritional   (Pharmacology as the study of substances found in founds in foods that might not be essential nutrients par se and garlic is believed top belong to this field.

The chemical structure of the related sulphur compound present in garlic is (CH2 = CHCH2)2 diatlyl disulphide, propienyl and methyl sulphide (C3 HS-S-SC3H5), dietlyl, disulphide is the first product of allicin when degraded by the enlymatic activity of alliance.

CH3CH = CH – S11 – CH2 – CH-COOH (All in)

+ H2O

Allicin has a pungent taste or flavour.  It is responsible for garlic antibiotic activity.






Weighing balance

Hot air Oven



Wire loop

Bunsen Burner


Cotton wool

Filter paper



Staining rack

Test tube racks

Alluminium caristers



          Observations on bacteria isolate culture plate and biochemical test helped to identify staphylococcus aureus. Based on:-

Pigmentation- The colour of the colony was yellow on blood agar and some where white, 1-2mm in diameter slightly raised.  B-haemolytic on Macconkey agar, pinkish, 0.1-0.5mm in diameter.  Gram positive, catalase positive, Coagulase positive,  manitol fermenting and non-lactose fermenting.

From sensitivity test, a slight or fainty zone of inhibitions were observed, which shows that staphylococcus  aureus. Was sensitive to garlic extract although the zone of inhibitions were fainty (i.e not well magnified) owing to the low concentration of garlic extract.  These zone of inhibitions as can be seen in FIG I and II at the previous page of this book were measured and compared with control drug of Nalixidic acid, Nitrofurantoin and Gentamicin with the value of each disc potency which shows a strong zone of inhibition on. staphy  aureus.




          Staphylococcus  aurues which was found to e sensitive to garlic extract (GE) has a mean zone of inhibition of various potencies from 30mg to 50mg which is equipmetn to urinary tract infection (UTI) antibiotics like Nalixidic acid, and Gentamycin as broad specstrum as shown in table IV, this is in agreement to Shelef,(1980).  Example, 30mg of garlic extract  (GE) with inhibition zone of 13mm is equivalent to 30mg of Nalididic drug inhibition zone of 13.5mm.  The highest mean h was compared with control drug, although the potencies are not the same is 50mg of high concentration  garlic extract (GE).

Crude extract which were found not active against the test organism as seen in table VI may be due to the fact that were singly and therefore may need to be mixed with other extracts of active ingredients to be active. The sensitivity of micro organisms to plant coponets are advanced from the world of antibiotics when used against other micro organism  can check the proliferation of microbial infection and are useful  for their control staphylococcus aureus culture rate which was discovered to be more prevalent in the age range of 18-30 years, could be attributed to unhygienic measure  and casual sex due to their sexual activeness in agreement Kunnin, (1979).  While there was low prevalence at the age range of 61-70 years.  Therefore,  Staphylococcus aureus causing infection of the skin and urinary tract infection (UTI) as shown by the result is sensitive to garlic extract at high concentration, which implies that the more concentration of extract, the higher the magnified zone of inhibition to be seen, which is also equivalent to more intake of garlic extract (GE), the more Staph  aureus  is to be sensitive to it.


From the sensitivity testing, Garlic extract which was found to be effective on Staph  aureus causing  skin and urinary tract infection among women have no record on the effect of too much intake except on much exposure to garlic dust based on commercial extraction level.  Then if one subject herself to garlic intake, there is every tendency of getting cured of staph  aureus causing skin and urinary tract infections.  To determine the max, mum potency that will be fixed as regards to other antibiotics regarded as antibacterial agent is the task ahead


Antibiotics like Nalidioxic acid, Nitrofurantoin and Genmntamycin were said to be effective against Staph aureus causing skin and urinary tract infection but  the drugs are costly.  This work has proud that high concentration of garlic extract is effective on staph aureus causing urinary tract infection and skin infections therefore, we recommended that:-

Further work be carried out to determine the normal dose that will be taken so that when one takes it, he/she will not experience adverse effect or hyperactivity.  Many people mostly women have been staking garlic as spice without the knowledge of its medicinal potency, in light of this we recommend that the governments should encourage public health /education on the potency of the cheap and readily available antibacterial agent like garlic and its addition to daily dietary will act as prophylactic drug especially to women in the case of Staphylococcus  aureus causing urinary tract infection and other skin diseases.

In order that a traditional folk could be fully accepted large scale controlled clinical trials must be enclosed and conducted by food drug Administration.

In the absence of  an altruistic pharmaceutical firms steeping forward, the government or a public oriented organization might take the initiative to test garlic and other such agents for their  therapeutic claims.  With this is will encourage the garlic champions of present to come forward to prove the medicinal worth of this pungent plant.

This  research work was limited to Staph  aureus­ alone and other research world should be carried out in other related bacterial like E. Co,  Bacillus species and salmonella typhyrium and  others.


  • ABAYOMI, S. (1982). Medicinal Plant and Traditional Medicine in Africa,
  • John Wily and Sons publishing company Ltd.  New York Pp. 2-3, 70-75 and 76-77.
  • ADAM, I.J. (1981), Hyperlipideamic effect of garlic (Allium sativum) journal of Biochemistry University of Karala Trivanda pp. 469-470
  • AUGUST, K.T. (1974), Hypocholestrolacmic effect of garlic Allium Sativum) Journal of Biochemistry university of Karala Trivandan pp. 487-490
  • AUGUST, K.T. (1977). Hypoglycaemic effect of garlic (fillium sativum) journal of Biochemistry) University of Karala Trivandan pp 204-208
  • BARLEY, J.F (1950). Allicin the anti-bacterial principle of Allium sativum I. Its isolation physical properties and anti bacterial action.  Journal of American chemical sociology pp 98-106



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