Abstract

Fresh fruits and vegetables promote good health but harbour a wide range of microbial contaminants. To assess the microbial quality of fruits and vegetables, twenty-eight (28) samples of different fruits and vegetables were purchased from various vendors. Samples were analyzed to study the density of microorganisms. The spread plate method was used for the isolation of bacteria on nutrient media. Mean bacterial load ranged from 4.4x106cfu/g to 1.07x107cfu/g with garden eggs recording the lowest count and cabbage samples harbouring more bacteria than the rest of the samples. Sliced watermelon samples recorded a mean viable count of 9.2x106cfu/g. Mean coliform count was highest in cabbage (7.4x104cfu/g) and lowest in pineapple (1.1x104cfu/g).  Six bacteria belonging to eight genera were identified. Staphylococcus aureus (82.1%) was the most frequently isolated followed by Salmonella species 13(46.4%), Bacillus species 12(42.9%), Enterobacter aerogenes 9(32.1%). Micrococcus species 6(21.4%) and Escherichia coli (25%) were the least frequently isolated. Resistance to a wide range of antibiotics was observed. Resistance to augmentin, cefuroxime, ceftazidime and ceftriaxone was observed as 100%, 100%, 100% and 69.2% respectively for the Salmonella isolates. Drug susceptibility assay revealed that 84.6%, 69.2%, 61.5% and 30.8% of the Salmonella isolates investigated were susceptible to ciprofloxacin, Ofloxacin, gentamicin and ceftriaxone respectively. Eighty-seven percent of the S. aureus isolates were resistant against erythromycin whereas 82.6% and 73.9% of the isolates were resistant to augmentin and ceftriaxone respectively. Resistance to ofloxacin was seen in 14.3% while 100% were resistant to Augmentin for the E. coli isolates. The presence of potential food-borne pathogens makes the fruits to be microbiologically unsafe and they should be pre- treated thoroughly before human consumption, so as to reduce the risk of food- borne outbreaks.

TABLE OF CONTENT 

Cover page i

Title page ii

Certification iii

Declaration iv

Dedication v

Acknowledgments vi

Table of contents vii

List of Tables x

Abstracts xi

CHAPTER ONE

1.1 Introduction 1

1.2 Aims and Objectives 6

CHAPTER TWO: LITERATURE REVIEW

2.1 An Overview of Fruits 7

2.2 Bacteria in Fruits as a cause of Disease 8

2.2.1 Risk associated with consumption of fruits (Microbial hazards) 9

2.3 Microbial Contamination 11

2.3.1 Soft Rot 12

2.4 Contamination Sources of Vegetables 12

2.4.1 Pre-Harvest Contamination 13

2.4.2 Quality of Irrigation Water 14

2.4.3 Post-Harvest Contamination 15

2.5 Common Fruits and Vegetable Spoilage Organisms 16

2.5.1 Listeria Monocytogenes 16

2.6 Global Relevance of Food Safety and Foodborne Illness 17

2.7 Food Poisoning 20

2.8 Antibiotics Resistance 21

CHAPTER THREE: MATERIAL AND METHODS

3.1 Sample Collection 23

3.2 Media Preparation 23

3.3 Preparation of Sample Homogenate 23

3.3.1 For The Isolation Of Salmonella Species 24

3.4 Gram Staining 25

3.5 Biochemical Tests 25

3.5.1 Catalase Test 25

3.5.2 Methyl Red Test 26

 3.5.3 Voges- Proskauer Test 26

3.5.4 Indole Test 26

3.5.5 Citrate Utilization Test 27

3.5.6 Hydrogen Sulphide (H2s) Production Test 27

3.6 Antibiotics Sensitivity Test 27

CHAPTER FOUR

Results 29

CHAPTER FIVE

5.1 Discussion 35

5.2 Conclusion 40

REFERENCES 41