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
LIST OF TABLES
|
S/N
|
TABLE
|
PAGE NO
|
|
1
|
Diameter Zone of Inhibition (mm) Produced after 3
Hours of Growth
|
31
|
|
2
|
Diameter Zone of
Inhibition (mm) Produced after 6 Hours of Growth
|
32
|
|
3
|
Diameter Zone of Inhibition (mm) Produced after 16
Hours of Growth
|
33
|
|
4
|
Minimum Inhibitory
Concentration and Maximum Bactericidal Concentration Value of Selected
Biocides against the Test Bacteria
|
34
|
CHAPTER ONE
1.0 INTRODUCTION
Biocides,
in the broadest sense, are substances formulated to be harmful to (or to
otherwise control) living organisms (Scenihr, 2009). Many authorities adopt
more restrictive definitions, similar to those for a microbicide, for the
purposes of considering non-antibiotic antimicrobial agents, albeit still with
diverse chemical characteristics and applications. Useful definitions in this
mould have been provided by (Tumah, 2009) and (Sheldon, 2005), which the
authors of the present review regard as reasonable in scope and practicality.
With few exceptions such as iodide salts that show some efficacy in the
treatment of certain veterinary fungal and bacterial infections (Fraser et al., 2001) biocides are not
sufficiently selective to be used within body tissues, but some may be used as
antiseptics on body surfaces. Other common applications include use as disinfectants
on equipment and surfaces in many environments including farms and hospitals,
as decontaminants on carcass surfaces following slaughter, as sporicidal
sterilants for medical equipment and as preservatives in pharmaceuticals,
cosmetics and food (Scenihr, 2009).
Antiseptics
and Biocides are used extensively in hospitals and other health care centres to
control the growth of microbes on both living tissues and inanimate objects.
They are essential parts of infection control practices and aid in the
prevention of nosocomial infections (Larson et al., 1991). But a common
problem is the selection of Biocides and antiseptics because different
pathogens vary in their response to different antiseptics or disinfectants
(Russell, 1996). Dettol is widely used in homes and healthcare settings for
various purposes including disinfection of skin, objects and equipments, as
well as environmental surfaces. With prior cleaning before application, the
number of microorganisms colonizing the skin and surfaces are greatly reduced
(Rutala, 1996). The antimicrobial properties of chloroxylenol, the main
chemical constituent of Dettol and other chlorinated phenols have been
extensively studied (Hugo and Bloomfield, 2001). The antimicrobial properties
of the disinfectant against some pathogenic bacteria have earlier been reported
(Mellefont et al., 2003). Moreover, microorganisms are continuously
acquiring resistance to new antiseptics and disinfectants; as a result, no
single antiseptic or Biocides will be appropriate for all pathogens (Tortora et
al., 1998). Therefore, it is necessary to evaluate the effectiveness of an
antiseptic or disinfectant against a specific pathogen so that an appropriate
agent can be easily selected. It is very important not only choose the
appropriate disinfectant if not show that the concentrations, time, temperature
and physical action that is used is efficient and profitable for those who use
them.
This
research demonstrated experimentally the effect of selected biocides on some
test organisms. Also obtain security in the process of disinfection using a
methodology of a standardized procedure. Entis, (2002), mentioned that the
disinfectant function is to destroy microorganisms and prevent the spread of
these. A disinfectant is a biocide that destroys the growth of microorganisms
on surfaces and inanimate objects (McDonnell and Russell, 2009). The mechanisms
of action of biocides, together with the factors that influence its activity,
has become a key feature for the best use of biocidal formulations and control
the emergence of resistant organisms (Gibson et al., 2009). It is considered that the active ingredients of the
biocides are generally products that may contain one or more actives principles.
Determining
the biocide efficacy is often carried out in suspension tests. This type of
test determines the concentration of disinfectant which shows a definite log
reduction in the number of microorganisms at a given time. In practice,
meanwhile, the microorganisms are subjected to disinfection of surfaces in food
production and that remains after cleaning, are commonly of the surface (Gibson
et al., 2009).
Since some microorganisms have gained
resistance to biocides due to mutation and resistance, lack of proper quality
control in the production of biocides will reduce the efficacy of the biocides
on microorganisms, considerations should be placed on concentrations of biocides
used to combat microorganisms. Biocide of choice is also to be tackled because pathogens
differ in their response to different Biocides.
The study of this work is for people to know
the effectiveness of some biocides used against microorganisms (Staphylococcus aureus and Escherichia coli), and also to know the
amount of concentration of a biocide that will inhibit the growth of
microorganisms. Minimum Inhibitory Concentration was used to determine the
lowest concentration of an antimicrobial that inhibit the visible growth of a
microorganism after overnight incubation and Minimum Biocidal Concentration
which is the lowest concentration of an antibacterial agent required to kill a
particular bacterium.
1.1 AIM AND OBJECTIVES
To determine the effect
of biocides on microbial growth rate (bacteria), while the specific objects
are;
· To determine the antimicrobial effect of
various biocides tested against the selected bacterial strains
· To determine the minimum biocide concentration
on selected pathogens
· To determine the minimum inhibitory
concentration of the various biocides on selected pathogens
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