Effect Of Biocides Onbial Growth Rate (Bacteria)

ABSTRACT

This study was to determine the effect of biocides on microbial growth rate. A total of Six (6) different household biocides (Dettol, Septol, TCP, Izal, Savlon and Ethenol) were screened for their efficacy to control microbial growth. Environmentally isolated Escherichia coli and Staphylococcus aureus as well as ATCC strains of both organisms (S. aureus, ATCC25923 and ATCC25922) were used in this study as test organisms. To determine the effect of the various biocides on the test organisms at times 6hrs, 12hrs and 16hrs, agar well diffusion technique was employed to evaluate/determine the potency of these biocides on the test organisms. Results from this study revealed that Savlon recorded the highest zones of inhibition against Staphylococcus aureus (26 mm) at 3 hours followed by Dettol (24mm), Septol (23mm), Izal (21mm) and Ethanol (15mm) at 6 hours time interval and the two pathogens (Staphylococcus aureus and Escherichia coli) were sensitive to Savlon and Dettol at different concentrations. Results of this experiment also indicated that different pathogens acquired resistance to disinfectants (TCP and at less extent ethanol), and also suggested that the antibacterial effects of these biocides are not only dependent on the types of disinfectant but also on their concentrations. Resistance against antibiotics by pathogenic bacteria is a major concern in the antimicrobial therapy for both humans and animals. The effectives of biocides are very important to enhance the antimicrobial activity of these disinfectants towards controlling microbial population which includes prevention of diseases transmission and infection.

TABLE OF CONTENTS

Title Page ﾿   ﾿   i

Certification ﾿ iii

Dedication ﾿ iv

Acknowledgement ﾿ v

Table of Contents ﾿ vi

List of Tables ﾿ vii

Abstract ﾿ ix

CHAPTER ONE

Introduction ﾿ 1

1.1 ﾿ Aim and Objectives ﾿ 3

CHAPTER TWO

Literature Review ﾿ 4

2.1 ﾿ Microbial Resistance to Biocides ﾿ 4

2.2 ﾿ Reduced Microbial Susceptibility to Biocides ﾿ 5

2.3 ﾿ Mechanisms by Which Biocide Exert Their Antimicrobial Action ﾿ 6

2.4 ﾿ Mechanisms Which Reduce Microbial Susceptibility to Biocides ﾿ 8

2.4.1 ﾿ Intrinsic Properties of Bacteria Conferring Reduced Susceptibility to Biocides ﾿ 8

2.4.2 ﾿ Reduced Susceptibility to Biocides Resulting from Phenotypic Changes ﾿ 11

2.4.3 ﾿ Plasmid-Mediated Mechanisms ﾿ 12

2.4.4 ﾿ Mutational Resistance to Biocides ﾿ 13

2.5 ﾿ Possible Links between Antibiotic Resistance and Reduced 

﾿ Susceptibility to Biocides ﾿ 14

2.5.1 ﾿ Examples of Studies Showing Reduced Susceptibility to Biocides in 

﾿ Antibiotic-Resistant Bacteria ﾿ 14

2.5.2 ﾿ Examples of Studies Showing No Change in Susceptibility to Biocides in 

﾿ Antibiotic-Resistant Bacteria ﾿ 15

2.6 ﾿ Active Substances ﾿ 16

2.7 ﾿ Production, Use and Fate of Biocides ﾿ 17

2.8 ﾿ Application of Biocides ﾿ 18

2.8.1 ﾿ Biocides (Disinfectants) on Medical Devices and Surfaces ﾿ 18

2.8.2 ﾿ Biocides (Disinfectants and Antiseptics) Used on Skin and Mucosa ﾿ 20

2.9 ﾿ Biocides in Consumer Products ﾿ 20

2.9.1 ﾿ General Aspects ﾿ 20

2.9.2 ﾿ Cosmetics and Personal Care Products ﾿ 21

2.9.3 ﾿ Household Products ﾿ 21

CHAPTER THREE

Materials and Methods ﾿ 23

3.1 ﾿ Sample Collection ﾿ 23

3.2 ﾿ Sterilization of Materials ﾿ 23

3.3 ﾿ Materials and Media Used ﾿ 23

3.4 ﾿ Media Preparation ﾿ 23

3.4.1 ﾿ Inoculation of Test Organisms ﾿ 24

3.5 ﾿ Biochemical Test ﾿ 24

3.5.1 ﾿ Catalase Test ﾿ 24

3.5.2 ﾿ Indole Test ﾿ 24

3.5.3 ﾿ Citrate Utilization Test ﾿ 24

3.5.4 ﾿ Hydrogen Sulphide (H2S) Production Test ﾿ 24

3.5.5 ﾿ Starch Hydrolysis ﾿ 25

3.5.6 ﾿ Motility Test ﾿ 25

3.5.7 ﾿ Voges-Proskauer Test ﾿ 25

3.5.8 ﾿ Urease Test ﾿ 26

3.5.9 ﾿ Methyl Red Test ﾿ 26

3.5.10 ﾿ Carbohydrate Fermentation ﾿ 26

3.5.11 ﾿ Coagulase Test ﾿ 27

3.5.12 ﾿ Oxidase Test ﾿ 27

3.6 ﾿ Biocides Testing ﾿ 27

3.6.1 ﾿ Determination of Biocidal Activity ﾿ 27

3.6.2 ﾿ Determination of Minimum Inhibitory Concentration and Minimum 

﾿ Bacteria Concentration ﾿ 28

CHAPTER FOUR

Results ﾿ 30

4.1 ﾿ Diameter Zones of Inhibition Produced After Three Hour ﾿ 30

4.2 ﾿ Diameter Zones of Inhibition Produced After Six Hours of Growth ﾿ 30

4.3 ﾿ Diameter Zones of Inhibition after Sixteen Hours of Growth ﾿ 31

4.4 ﾿ Minimum Inhibitory Concentration and Minimum Bactericidal Concentration 

﾿ Value of Selected Biocides against the Test Bacteria ﾿ 31

CHAPTER FIVE

Discussion, Conclusion and Recommendation ﾿ 35

5.1 ﾿ Discussion ﾿ 35

5.2 ﾿ Conclusion ﾿ 37

5.3 ﾿ Recommendation ﾿ 37

﾿ References