ABSTRACT

The study of minimum inhibitory concentration, minimum bactericidal concentration and the killing time of ethanol, sodium hypochlorite and hydrogen peroxide on Staphylococcus aureus was carried out. The test organism, Staphylococcus aureus was isolated from the nasal cavity of humans. The media used was nutrient agar, streak plate method was employed. Colonial morphology, Gram staining and biochemical tests were used in the identification of the test organism, Staphylococcus aureus. Ethanol, Sodium hypochlorite and Hydrogen peroxide were utilized as disinfectants in this study. The study of the minimum inhibitory concentration, minimum bactericidal concentration  and the killing time of these three disinfectants was conducted on Staphylococcus aureus using the tube dilution method (Quantitative method) under the time intervals of 3, 7 and 10 minutes respectively. The killing time of ethanol at concentration of 70%, 80% and 95% was at 10 minutes. For sodium hypochlorite, at concentrations of 1% and 2%, the killing time was 10 minutes while at 3% concentration, the killing time ranged from 7 and 10 minutes. For Hydrogen peroxide, at 5% concentration, the killing time ranged from 7 and 10 minute while at concentration 10% and 15%, the killing time ranged from 3, 7 and 10 minutes. At the different concentrations of ethanol used, the minimal bactericidal concentration and minimal inhibitory concentrations were 1000µl/ml and 250µl/ml respectively. At 15% concentration, hydrogen peroxide showed the least values of minimum bactericidal concentration and minimum inhibitory concentration which were 500µl/ml and 62.5µl/ml respectively. At 5% concentration, hydrogen peroxide showed the highest values of minimum bactericidal concentration and minimum inhibitory concentration at 2000µl/ml and 250µl/ml respectively. The minimum bactericidal concentration and minimum inhibitory concentration of 1% Sodium hypochlorite were at 2000µl/ml while 2% and 3% had similar effect in terms of the minimum inhibitory concentration and minimum bactericidal concentration which occurred at 2000µl/ml and 1000µl/ml respectively. The results showed that 15% Hydrogen peroxide had the highest efficacy against Staphylococcus aureus, both during the determination of the killing time and in the determination of the minimum inhibitory concentration and minimum bactericidal concentration while 1% Sodium hypochlorite which showed both minimum inhibitory concentration and minimum bactericidal concentration at 2000µl/ml had the least efficacy against Staphylococcus aureus.

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgements iv

Table of Contents v

List of Tables vi

List of Figures vii

Abstract viii

CHAPTER ONE

1.0 Introduction 1

1.1 Justification of the study 5

1.2 General aim of the study 5

1.3 Objectives of the study 6

CHAPTER TWO

2.0 Literature Review 7

2.1 History of Disinfectants 8

2.2 About Disinfectants 9

2.3 Sources of Contamination of Surfaces 9

2.4 Types of Disinfectants 10

2.4.1 Non-oxidizing disinfectants 10

2.4.2 Alchohols 11

2.4.3 Aldehyde 12

2.4.4 Phenol 12

2.4.5 Quaternary ammonium compounds 13

2.4.6 Oxidizing agents 13

2.4.7 Sodium hypochlorite 14

2.4.8 Chlorine dioxide 14

2.4.9 Hydrogen peroxide 14

2.4.10 Iodine 15

2.4.11 Peracetic acid 15

2.4.12 Home disinfectants 15

2.5 Properties of a Disinfectant 17

2.6 General Features of Disinfectant 17

2.7 Factors influencing the efficacy of disinfectant 20

2.8 General Features of the Test Organisms 21

2.9 Mechanism of Actions of Disinfectants against Bacteria 22

2.10 Resistant Action of Bacteria 23

2.10.1 Staphylococcus aureus sensitivity 24

2.11 Advantages and Disadvantages of Disinfectants 24

2.11.1 Advantages 24

2.11.2 Disadvantages 26

2.12 General Guidelines in the Use of Disinfectants 27

CHAPTER THREE

3.0 Material and Method 29

3.1 Study area   29

3.2 Sources and concentration of disinfectants used 29

3.3 Preparation of different concentration of disinfectants 29

3.4 Media used 31

3.5 Collection of test sample and isolation 31

3.6 Biochemical identification of bacteria isolate 31

3.6.1 Gram staining 32

3.6.2 Catalase test 32

3.6.3 Coagulase test 32

3.7 Materials 33

3.8 Killing time of different dilutions of the disinfectant used in this study

 using suspension test 33

3.9 Minimium inhibitory concentration 34

3.10 Minimium bactericidal concentration 34

CHAPTER FOUR

4.0 Results 35

CHAPTER FIVE

5.0 Discussion 41

5.1 Conclusion 42

5.2 Recommendations 43

References

Appendix