ABSTRACT

The antibacterial effect of aqueous and ethanolic extract of onion (Allium cepa) and Garlic (Allium sativum) applied singly as well as in combination on five intestinal bacteria (Escherichia coli, Salmonella, Shigella, Proteus and Enterobacter) was evaluated. The  paper disc diffusion method was adopted at different concentrations (10%, 25%, 75% and 100%). The result showed variable effect against the bacterial isolates. The extracts of these Allium plants (Garlic and Onion) exhibited marked antibacterial activity with the garlic extracts showing the highest inhibition. The highest inhibitory effect of the aqueous onion extract was seen against E. coli with a zone of inhibition of 6mm while the least was seen against Proteus which gave a zone of inhibition of 2mm. All isolates were resistant at concentrations below 100%. The ethanolic extract of the onion plant yielded a better antibacterial activity as the isolates showed resistance for the concentrations below 75%, Escherichia coli and Enterobacter showed more sensitivity as they gave an inhibition zone of 12mm respectively for the 100% concentration, the least was Proteus which gave a zone of inhibition of 6mm. E.coli and Enterobacter showed more sensitivity to the 75% concentration with 10mm each, while Proteus showed the least sensitivity of 2mm. The aqueous garlic extract gave a better inhibition than that of the onion extract. The isolates showed resistance for the concentrations below 75%, Escherichia coli and Salmonella showed a higher sensitivity for the 100% concentration with 13mm and 12mm zone of inhibition respectively, while both had 10mm respectively for the 75% concentration. Proteus showed less sensitivity as it gave the least inhibition zone of 6mm and 2mm at 100% and 75% concentration respectively. The ethanolic garlic extract showed the highest inhibition on the isolates. All isolates showed resistance for the concentration below 25%, except for Proteus which showed inhibition for the concentration below 75%, E. coli and Salmonella were inhibited most, as they showed inhibition zone of 14mm and 10mm at 100% respectively, 11mm and 8mm at 75% respectively and 4mm respectively for the 25% concentration. Proteus was less sensitive, it showed inhibition zone of 8mm and 7mm for 100% and 75% concentrations respectively. All isolates were resistant to gentamicin(the control) while the aqueous extracts of both plants combined showed greater antibacterial effect, with Escherichia coli being highly sensitive with 20mm inhibition zone and Proteus less sensitive with 12mm inhibition zone. The results therefore suggest that these extracts can be used to treat intestinal pathogens confirming the traditional claim that the Allium plants possess antibacterial properties.          

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgement iv

Abstract v

Table of Contents vi

List of Tables viii

List of Figures viii

CHAPTER ONE

1.1 Introduction 1

1.2 Aims and Objectives 2

CHAPTER TWO

2.1 Literature Review 4

2.2 Onion (Allium Cepa) 4

2.2.1 Historical origin/distribution  4

2.2.2 Taxonomic classification 5

2.2.3 Plant description 6

2.2.4 Nutritional Value 6

2.2.5 Culinary Uses of Allium Cepa 6

2.2.6 Medicinal Uses of Alium Cepa 7

2.3 Phytochemicals in Allium cepa/ antibacterial properties 8

2.3.1 Organosulfur Compounds 8

2.3.2 Flavonoids 9

2.4 Allium sativum (Garlic) 10

2.4.1 Historical origin/distribution 10

2.4.2 Taxonomic classification 10

2.4.3 Plant Description 11

2.4.4 Nutritional Value 11

2.4.5 Culinary Uses of Garlic (Allium sativum) 12

2.4.6 Medicinal values of Allium sativum 12

2.5 Phytochemicals in Garlic/Antibacterial Properties  15

2.6 Intestinal pathogens      16                                                                                                                                          

CHAPTER THREE: MATERIALS AND METHOD

3.1 Sample Collection 17

3.2 Confirmation of Isolates 17

3.3 Characterization and Identification 17

3.4 Media Preparation 17

3.5 Sterilization 17

3.6 Extraction Procedure 24

3.7    Susceptibility Testing 25

CHAPTER FOUR

4.1   Result 27

CHAPTER FIVE

5.1 Discussion 35

5.3    Conclusion 36. 

5.2   Recommendation 37

REFERENCES 38

LIST OF TABLES

TABLE                                              TITLE                                                                 PAGE

1: Effect of aqueous onion extract on the test organisms 29

2: Effect of ethanolic onion extract on the test organisms 30

3: Effects of aqueous garlic extract on the test organisms 31

4: Effects of ethanolic garlic extract on the test organisms 32

5: Synergistic effect of aqueous onion and garlic extracts on test organisms 33

6: Characterization of Bacterial Isolates 34