ABSTRACT
To access the role of biocide in the environment and the impact of biocide resistance, a panel of biocides was evaluated for antimicrobial activity and biocide resistance patterns. Equally, plants with traditionally acclaimed biocidal activities were accessed. The samples were subjected to Disc susceptibility testing, minimum inhibitory concentration (MIC) and time-kill determination. Majority of the population use household commercial biocides including benzalkonium chloride, sodium hypochlorite, sodium carbonate, chlorophenol, choroxylenol and ammonium as well as isoprppyl alcohol and other respective combinations. Preliminary data on zone of inhibition at 1mg/L(v/v) against standard E. coli and S. aureus strains for benzalkonium (Harpic®), sodium hypochlorite( Jik®), chloroxylenol (Dettol®) and chlorophenol (Ivy fectant®) were all resistant at < 19mm S. aureus except dettol and Izal, including Izal towards E. coli >17mm respectively. Xylopia was the only botanical that showed biocidial activity against E.coli >18mm. Xylopia, Azadiracha and Vernonia only showed moderate antistaphylococcal activity at high MIC value (1,024mg/L). Comparatively, Izal B had the highest to moderate inhibition effect against E. coli in the following manner Izal> Harpic > Dettol > Jik at 0 hr, while Ivy detergent didnt show biocidal activity at 0 hr contact both at MIC or double MIC value. The double MIC biocide-bacterial time-kill effects were very pronounced and consistent among all the biocides suggesting that higher effect of biocides could only be enjoyed at higher concentrations and longer time contact with the oragnism. This suggests that when applying household biocide, high concentration and more time factor is needed in other to act on the applied area and to achieve inhibition of bacterial growth. The fact that biocides are used extensively in many different products and concentration contribute largely to its efficacy, while at lower dosage usage and less time contact, it remain inactive allowing the organisms to overcome the effect and thereby contribute to bacterial resistance.
TABLE
OF CONTENTS
Title
Page i
Certification ii
Dedication iii
Acknowledgement iv
Table
of Contents v
List
of Tables vi
List
of Figures vii
Abstract viii
CHAPTER ONE 1
1.0 INTRODUCTION 1
1.1
Examples showing links between Antibiotic and Biocide Resistance 2
1.2What
is Biocide?
6
1.3
What is Resistance?
6
1.4
What is biocide resistance?
6
1.5
Mechanisms of biocide resistance
7
1.6
Mechanisms of intrinsic bacterial resistance to biocide 8
1.7
Mechanism of acquired bacterial resistance to biocides
10
1.8
Common resistance mechanism of both biocide and Antibiotic 11
1.1.1
Research Justification
13
1.1.2 Aim and Objectives of the study
14
CHAPTER TWO 15
2.0
Literature Review
15
2.1
chemicals used as ingredient in biocide
16
2.2
Jik
17
2.3
Dettol
18
2.4
Nittol
18
2.5
Harpic Active fresh
19
2.2.1
Ivy’s Antiseptic
20
2.2.2
Dettol hand sanitizer and Mum and me hand gel
21
2.2.3
Izal (Z Germicie)
21
2.2.4
Botany of plants investidated for biocidal activity
22
2.2.5
Ricinus communis
22
2.2.6
Jatrophy curcas L. 23
2.2.7Azadirachta
indica (Neem)
24
2.2.8
Vernonia amydalina 26
2.2.9
Piper guineense
27
2.3
Xylopia aethiopica
28
2.4
Cassia alata
28
2.5Thinlayer
chromatography 29
CHAPTER THREE 31
3.0 MATERIALS AND METHODS 31
3.1
Study Area 31
3.2
Biocide/ Plant collection and identification 31
3.3
Preparation of extracts 31
3.4
Preparation of Biocides 32
3.5
Diameter zone of inhibition determination of the biocides
33
3.6
Preparation of test organism 33
3.7
Minimum inhibitory concentration (MIC) determination
33
3.8
Determination of Time – kill curve method 34
3.9
Thin layer chromatography 35
CHAPTER FOUR 36
4.0 RESULT 36
4.1
Antimicrobial activity of the household biocide
36
4.2
Result of MIC determination of biocides and plant extracts 40
4.3
Effect of time- kill determination of the biocides 42
4.4
Thin layer chromatography (TLC) 44
CHAPTER FIVE 47
5.0
DICUSSION AND CONCLUSION
47
5.1
Discussions 47
5.2
Conclusion 49
5.3
Recommendation 51
References
Appendix: Abstract and certificate of
scientific presentation
LIST OF TABLE
Table
1: Antimicrobial activity of the selected Household biocide against Escherichia coli and Staphylococcus aureus
Table
2: Antimicrobial activity of the selected plant extract against Escherichia coli and Staphylococcus aureus
Table
3: Minimum inhibitory concentration of
commercial household biocide.
Table
4: Minimum inhibitory concentration of
extract against S. aureus
Table
5: The effect of time – kill on
activities of the biocides
Table
6: Various retention faction as observed
on the TLC plates of different phytochemicals present in the each extract.
LIST OF FIGURES
Fig.1: Bargraph
showing the time-kill effect of the E. coli biocides combination at 0 hr at A
(single MIC of each biocide) and B (double MIC)
Fig. 2: Bargraph
showing the time-kill effect of the E. coli biocides combination at 24 hr at A
(single MIC of each biocide) and B (double MIC)
LIST OF PLATES
Plate 1: Diagram
showing Jik detergent used for household cleaning
Plate2:
Diagram showing Dettol detergent used for household
cleaning
Plate 3: Diagram
showing Nittol powder used as household detergent
Plate 4: Diagram
showing Harpic detergent
Plate5:
Diagram showing Ivy detergent
Plate 6a
&b: Diagram of Dettol and Mum & Me hand gel
Plate 7: Diagram of Izal germicide
Plate 8:
Diagram Ricinus communis
Plate
9: Diagram Jatropha curcas
Plate
10: Diagram of Azadiracha indica
Plate
11: Diagram of Vernonia amygdalina
Plate
12: Diagram of piper guineense
Plate
13a - 13d: Xylopia aethiopica
Plate
14 A: Diagram of Senna alata
Plate
15: Diagram of different diameter of zones of inhibition
Plate
16: Experimental set up showing a deep blue coloration. Clear tubes indicates
no bacterial growth and deep blue
coloration indicate growth. MIC is the least inhibition concentration .
Plate
17: Spotted plate showing various separation in TLC tank
Plate
18: TLC plates showing separation of extracts
CHAPTER ONE
INTRODUCTION
The
term biocide includes disinfectants, antiseptics, and preservatives. Biocides
are chemicals designed to kill all sizes and life stages of organisms,
especially micro- organisms, effectiveness of biocide varies with the
concentration of a biocide and duration of exposure (Akimitsu et al., 1999). Species that are exposed
to sub- lethal concentrations, or for too short of time may be injured but may
survive. Biocides are used for drinking water treatment, waste water treatment,
ship ballast water treatment, disinfectants and as antifouling agents that
prevent mollusks from accumulating in industrial pipes. Biocides are produced
in liquid and powder forms, in ready- to- use formulations or as concentrates,
and are applied using a variety of techniques. It does not include antibiotics,
which in spite of being in the strictest sense, tend to be categorized
separately. In recent years there has been a trend towards use of biocides in
the home environment, schools (especially in day care centers), and the number of
chemicals in antibacterial products are enormous, probably at least 10,000 with
1,000 commonly used in the hospitals and homes (Levy, 2001). These products
have been marketed for decontamination of food preparation surfaces (e.g.
Dettox), area perceived to be microbial contaminated (e.g. toilets) and general
improvement cleanliness in the home. A product called microban is a biocide
(triclosan) that is incorporated into chopping boards, knife handles and
wellington boots. Several workers have suggested that widespread use of
biocides may impact on the prevalence of antibiotics resistance micro-
organisms.
Biocide
resistance was first recognized nearly 70 years ago by ( Heathman et al., 1995a), which identified
chlorine resistance in Salmonella typhi
while antibiotic resistance was identified shortly after the availability of
penicillin, (Heathman et al., 1995b) but links between the two have only
been recognized more recently. It is remarkable that there is a large amount of
data on antibiotics resistance, yet there is a comparatively small number of
workers worldwide who are investigating the mechanism of biocides resistance.
Because biocides tend to act concurrently on multiple sites within the micro –
organism, resistance is often mediated by non- specific means.
1.1 EXAMPLES SHOWING
LINKS BETWEEN ANTIBIOTIC AND BIOCIDE RESISTANCE
(Manzoor
et al., 2009) demonstrated ethambutol
resistance in strains of Mycobacterium
chelonae that has selected in vitro
to be resistance glutaraldehyde. This resistance was associated with changes in
the composition of the cell well, indicating that reduced permeability may be
the mechanism for this cross resistance. These links between biocide and
antibiotic resistance are not confined toa typical Mycobacteria, and it has been shown that resistance to the
benzalkonium chloride is closely linked to oxacilline resistance in Staphylococcus aureus. (Akimitsu et al.,, 1999) reported that
benzalkonium chloride resistant mutants of methicillin resistant Staphylococcus aureus (MRSA) had
oxacillin MICs as high as 512mg/l, composed with 16mg/l for the parent strain
and 0.3mg/l for methicillin susceptible Staphylococcus
aureus (MSSA). Furthermore, resistance to plasmid can be mediated. A strain
of gentamicin resistant (MRSA) was shown to contain a multidrug resistant
plasmid (PSAJI) that conferred resistance to aminoglycosides, ethidium bromide,
benzalkonium chloride and chlorhexidine. This plasmid, when transferred to E. coli, continued to express resistance
to the same biocides as when in the original host. Plasmid mediated resistance
to biocides is a well-recognized phenomenon. Such as to quaternary ammonium
compounds and other biocides has been identified in Staphylococcus aureus ,Pseudomonas
spp and members of the Enterobacteriaceae,
and is mediated by specific genes (qacA,B,C,D and E) qacA,BandC (described in S.auerus) mediated resistance by an
active efflux mechanism and have sequence homology with tetracycline efflux
genes. qacE is a plasmid mediated resistance gene found in gram negative
organisms that also codes for an energy dependent multidrug efflux mechanism.
These resistance determinants are associated with resistance to a variety of
antibiotics including trimethoprim, sulphonamides, oxacillin and
aminoglycosides.
The
public is bombarded with advertisements advocating the use of biocides in the
home. The implication is that homes are dangerous places, heavily contaminated
with virulent microorganisms, and the only way to ensure the safety of one’s
children is to use disinfectant liberally. This engenders a false sense of security
in the public mind by suggesting that the widespread use of biocide reduces the
chance of acquiring infectious diseases. There are no data to support this
stance; rather, as biocide use in the home environment continues to increase.
There is a real risk that widespread biocide use could exacerbate the already
worrying trend towards increased antimicrobial resistance in clinically
relevant organisms. The problem is that we do not yet know how great the
problem is, or even if a problem exists. There are no good epidemiological data
on the impact of biocide use on antimicrobial resistance, and our knowledge of
the prevalence of antimicrobial resistance is still poor.
In
order to understand and control biocide resistance it is essential that more
effort is put into surveillance so that we can understand the impact of the use
of antimicrobial agents on the epidemiology of resistance organisms. Resistance
to biocide is less common and likely reflects the multiplicity of targets
within the cell as well as the general lack of known detoxifying enzymes.
Resistance
typically results from cellular changes that impact on biocide accumulation,
including cell envelope changes that limit uptake, or expression of efflux
mechanisms. Still, target site mutations leading to biocide resistance, though
rare, are accommodating biocide (e.g. triclosan) such that strains expressing
these are both antibiotic and biocide resistant (Russell, et al., 2002). Efflux pumps
have the potential to act on a range of chemically dissimilar compounds and
have been implicated in both biocide and antibiotic- resistance bacteria. Cell
wall changes may also play a role in the observed cross- resistance between
biocides and antibiotics, probably by reducing permeability. Microbial changes
that result in resistance to biocides should therefore cause concern. However,
of equal significance, is the possibility of genetic linkage between genes of
biocides resistance and those for antibiotic resistance.
Much
later, iodine found use as wound disinfectant, chlorine water in obstetrics,
alcohol as a hand disinfectant and phenol as a wound dressing and in antiseptic
surgery. In the early part of the twentieth century, other chlorine releasing
agents (CRAs), and acridine and other dyes where introduced, as were some
quaternary ammonium compounds (QACs, although these were only used as biocides
from the 1930s). Later still, various phenolic and alcohols, formaldehyde and
hydrogen peroxide were introduced and subsequently (although some had actually
been produced at an earlier date)biguanides, iodophors, bisphenols, aldehydes,
diamidines, isocyanurates, isothiazolones and peracetic acid. It has been
claimed that the chronological emergence of qacA and qacB determinants in
clinical isolates of Staphylococcus
aureus mirrors the introduction and usage of cationic biocides, (Russell et al.,, 1997).If everything else is
constant, then the more concentrated the biocide the greater its efficacy and
the shorter the time necessary to kill all the micro-organisms. Not all biocide
are similarly affected by concentration adjustments. In order words, halving
the concentration may double the exposure time for some biocides but quadruple
it for others. It is particularly important to ensure that disinfectants do not
become diluted with excess water remaining on endoscopes after rinsing, as the
activity of the disinfection process will be significantly compromised. Thus,
it is important that water is purged from all channels after cleaning and
before disinfecting and to regularly monitor the concentration of biocide when
it is being reused. The potency of a biocide affects the exposure time required
to achieve the same level of microbial kill. Several physical and chemical
factors influence the efficacy of biocides. These include; temperature, ph,
relative humidity and water hardness.
Generally,
the activities of most biocides increase as the temperature increases as the
temperature increases. There is a point at which the chemical degrades if
heated too much. An increase in ph improves the antimicrobial activity of some
agents as with glutaraldehyde, but decreases the activity of others such as hypochlorite.
This effect is caused either by alteration of the germicidal molecule or the
cell surface of the micro organism. Relative humidity influences the activity
of gaseous agents such as ethylene oxide. Water hardness reduces the rate of
kill of biocide because divalent cation such as magnesium and calcium interact
with soap to form insoluble precipitates. Organic matter such as serum, blood,
pus or faecal material may interfere with the activity of biocides in at least
two ways; first, a chemical reaction between biocide and organic matter may
result in a complex that is les germicidal or non germicidal leaving less of
the active agent to attack the micro organisms. Secondly, organic material many
protect microorganisms from attack by acting as a physical barrier. This is
another reason for the meticulous cleaning of object before any sterilization
or disinfection procedure.
To
adequately sterilize or disinfect an item, it must be exposed to the
appropriate concentration of biocide for a certain minimum contact time. All
surfaces of the item must come in contact with the biocide for that period of
time. This means that for endoscopic equipment the biocide must be introduced
into all lumens and channels. Presence of air pockets and incomplete immersion
in the biocide means item will not be reliably or completely processed.
1.3 WHAT IS BIOCIDE?
According to the direction 98/8/EC of the
European parliament and council of the 16 February 1998. Biocides are defined
as active substance and preparations containing one or more active substance,
put up in the form in which they are supplied to the user, intended to destroy,
render harmless, prevent the action of or otherwise exert a controlling effect
on any harmful organism by chemical or biological means.
The
active substance are without concern {Annex IA of the directive} or with
concern about their inherent capacity to cause an adverse effect on humans,
animals or the environment.
1.4 WHAT IS RESISTANCE?
Resistance
is the ability of micro-organisms of certain species to survive or even to grow
in the presence of a given concentration of an antimicrobial agent that is
usually sufficient to inhibit or kill micro-organisms of the same species.
1.5 WHAT IS BIOCIDE
RESISTANCE?
Biocide
resistance occurs when a biocide lost its effectiveness to kill or inhibit
microbial growth. Thus, the bacteria are resistant and continue to multiply.
1.6 MECHANISMS OF BIOCIDE
RESISTANCE
Biocides
have multiple target sites against microbial cells. Thus, the emergence of
general bacterial resistance is unlikely to be caused either; (i) by a specific
modification of a target site or (ii) by a by- pass of a metabolic
process. It emerges from a mechanism /
process causing the decrease of the intercellular concentration of biocide
under the threshold that is harmful
to the bacterium. Several mechanisms based on this principle (mode of
action) have been well described including change in cell envelope change in
permeability, efflux and degradation. It is likely that these mechanisms
operate synergistically although very few studies investigating multiple
bacterial mechanisms of resistance following exposure to a biocide have been
performed. The efficacy of biocides depends on a range of intrinsic and
extrinsic factors, (EFSA, 2008a) Intrinsic factors are characteristics of the
biocidal agent and its application, concentration and contact time are crucial.
Furthermore, the combination of contact time and concentration determine the
result in term of microbial reduction. This is called the CT concept, and
within certain limits of time and concentration, there is a relationship with a
defined constant characterizing efficacy. Thus, the same result could be
obtained with a high concentration of disinfectant during a short contact time,
or a lower concentration during a longer contact time. The stability of the
active compounds of the biocide in the environment also influences the
efficacy. Extrinsic factors derive from the environment during application. The
temperature of the environment is important, as mort substance have a lower
efficacy at low temperature. The
presence of protein reduces efficacy as they interact with the substance. The
mode of contact also influences the efficacy, as does the contact time
(mechanical effects). The ph is another important factor. The concentration of the micro organism, the
age of the bacterial community and protection by attachment on particular
matter, and the presence of biofilms play an increasing important role.
1.7 MECHANISMS OF
INTRINSIC BACTERIAL RESISTANCE TO BIOCIDES
Several
mechanisms conferring bacterial resistance to biocides have been described;
some are inherent to the bacterium, others to the bacterial population. In
addition, some of the resistance mechanisms are intrinsic (or innate) to the
micro organism while others have been acquired through forced mutations or
through the acquisition of mobile genetic elements (Poole 2002a). Innate
mechanisms can confer high level bacterial resistance to biocides. In this
case, the term insusceptibility is used. The most described intrinsic
resistance mechanism is changes in the permeability of the cell envelope, also
referred to as “permeability barrier”. This is not only found in spores (Cloete
2003,and Russell et al.,, 1997), but
also in vegetative bacterial such as mycobacteria and to some extent in Gram
negative bacteria. The permeability
barrier limits the amount of a biocide that enters the cell, thus decreasing
the effective biocide concentration (Denyer and Lambert 2002). In mycobacteria
the presence of a mycolarabinogalactan layer account for the impermeability to
many antimicrobials (Lambert 2002, Russell 1996, Russell et al.,, 1997). In addition, the presence and composition of the
arabinogalaitan ?arabinomannan cell also plays a role in reducing the effective
concentration of biocide that can penetrate within mycobacteria (Manzoor et al.,, 1999).
The
role of the lipopolysaccharides (LPs) as a permeability barrier in Gram
negative bacteria has been well documented (Denyer and Maillard 2002, McDonnell
et al.,) There have also been a number of reports of reduced biocide efficacy
following changes in other components of the outer membrane ultra structure including
proteins (Brozel and Cloete 1994). Fatty acid composition (Guerin-Mechinet al.,, 1999) and phospholipids. It
must be noted that in the above mentioned examples, an exposure to biocides was
followed by changes in ultra structure related to a decrease in biocidal
susceptibility, usually at a low concentration (under the MIC value). The charge property of the cell surface also
plays in bacterial resistance mechanisms to positively charged biocides such as
QACs. It is likely that bacterial resistance emerges from a combination of
mechanisms (Tattawasart et al., 2000),
even though single specific mechanisms are often investigated. The presence of
efflux pumps is another mechanism that has been well described in the
literature. It has gained increased recognition as a resistance mechanism over
the past decade. Efflux pumps decrease the intercellular concentration of toxic
compounds, including biocides (Borges - Walmslay 2001, Levy2002and Putman et al.,, 2000). They are widespread
among bacteria and five main classes have been identified: the small multidrug
resistance (SMR) family (now part of the drug / metabolite transporter (DMT)
super family), the major facilitator super family (MFS),the ATP – binding
cassette ( ABC) family, the resistance nodulation division ( RND) family and
the multidrug and toxic compound extrusion (MATE) family (Borges – Walmsley,
2001 and,Poole 2004,). The importance of efflux pumps in terms of bacterial
resistance to biocides might be considered as modest since the increase in
bacterial susceptibility to select biocides as the results of the expression of
efflux pumps is usually measured as an increase in MICs rather than as
resistance to a high concentration of an active substance. Efflux pumps have
been shown to reduce the efficacy of a number of biocides including QACs,
phenolics parabens and intercalating agents notably in staphylococcus aureus with identified pumps such as QacA-D, QacG
and QacH s and in Gram negative bacteria such as pseudomonas aeruginosa, with
MexAB – OprM, MexCD – OprJ, MexEF – OprN and MexJK(Poole 2004,) and Escherichia coli with AcrAB – ToIC,
AcrEF – ToIC and EmrE (McMurry et al., 1998a ). The enzymatic transformation of biocide has
also been described as a resistance mechanism in bacteria, notably to heavy
metal (e.g. silver and copper, enzymatic reduction of the cation to the metal, (Cloete2003);
parabens, aldehydes formaldehyde dehydrogenase, (Kummerle et al., 1996), peroxygens catalase, super oxide dismutase and
alkyl, hydroperoxidases mopping up free radicals, (Demple 1996). Environmental
bio-degradation of various compounds has been well described notably among
pseudomonas and complex microbial communities.
However, the importance of degradation as a bacterial resistance mechanism
to “in use” concentrations (high concentrations) of biocides remain under. As for efflux, increased resistance following
degradation of biocides has been measured as s decreased in MICs but not
necessarily as a decreased in lethal activity.
The modification of target sites has been described on rare occasions
and does not seem to be widespread among bacterial, although there is a paucity
of information on this subject. The bisphenoltriclosan has been shown to
interact specifically with an enoylacyl reductase carrier protein at a low
concentration (Healthet al., 1999). The modification of this enzyme has been
associated with low level bacterial resistance (Health et al., 2000, McMurry et al.,
1999). It has been noted that at a high concentration triclosan must interact
with other targets within the cell, the alteration of which justified the
lethal effect of the bisphenol (Gomez Escalada et al., 2005a).
1.8 MECHANISMS OF
ACQUIRED BACTERIAL RESISTANCE TO BIOCIDES
The
development of bacterial resistance through acquired mechanisms such as
mutation and the acquisition of resistance determinants are of concern since a
bacterium that was previously susceptible can become insusceptible to a
compound or a group of compounds (Russell 2002a). The acquisition of resistant genes has been
well described in the literature (and it is particularly important to consider,
this as it might confer cross or co – resistance on occasion (Poole 2004).
However, there is little information on the effect of biocides on the transfer
of genetic determinants. One study in particular highlighted that while some
biocides at a sub-inhibitory (residual) concentration could inhibit genetic
transfer, others increased genetic transfer efficiency. There have been
investigations on co- transfer of resistant markers in epidemic methicillin
resistant Staphylococcus aureus
following antibiotic treatment to decolonize patients (Cookson et al., 1991a). The authors reported
that there was no evidence of increased in chlorhexidine MICs six years after
the first isolation of the epidemic strains, although the strain carried a qac
gene (Cookson 2005).
However,
this was not the case with triclosan, where clinical isolates of Staphylococcus aureus showed high level
mupirocin resistance and low level triclosan resistance (MlC 2- 4 mg/l)
(Cookson et al., 1991b). The authors
described that resistance to both chemically unrelated compounds was
transferred and cured together (Cookson 2005).
1.9 COMMON RESISTANCE
MECHANISMS OF BOTH BIOCIDE AND ANTIBIOTICS
Considerable
controversy surrounds the use of biocides in an ever increasing range of
consumer products and the possibility that their indiscriminate use might
reduce biocide effectiveness ant alter susceptibilities towards antibiotics (Gilbert
and McBain 2003). These concerns have been based largely on the isolation of
resistance mutants from in-vitro monoculture experiments. Some of the evidence
suggests that exposure to biocides may be leading to increased antibiotic
resistance, but the number of studies in the clinical or environmental setting
is low.
However,
a recent study performed in the community highlighted a significant
relationship between high QAC MICs, high MICs to triclosen and resistance to
one or more antibiotics. Further research is needed to establish a correlation
between biocide exposure(s) and development of antibiotic resistance. Biocides
that tend to act concurrently on multiple sites within the micro organism and
thus resistance is often mediated by non-specific means. Efflux pumps have been
shown to cat on a range of chemically dissimilar compounds and have been
implicated in both biocide and antibiotic resistance bacteria (Maillard 2007
and Poole 2007). Cell wall changes by reducing permeability may also play a
role in the observed resistance to biocide. The possibility of genetic linkage
between genes for biocide resistance and for antibiotics resistance has also
been described.
Several
publications and reviews have presented the cell target of biocides and the various
mechanism used by the bacterial cell to evade the toxic activity of biocides (Denyer
and Maillard 2002, Lambert 2004, Maillard 2007, Poole 2007).it is important to
note that antibiotics and biocide antibacterial actions show many similarities
despite some differences in terms of target, killing, behavior and clinical aspects
(Poole 2007).among the similarities, we can mention;
i.
The penetration/uptake
through bacterial envelope by passive diffusion;
ii.
The effect on the
membrane integrity and morphology;
iii.
The effect on diverse key
steps of bacterial metabolism (replication, transcription, translation,
transport, various enzymes).
Faced
with this toxic effect and stress, the responses, adaptation of bacterial cells
presents some similar defense mechanisms that can overlap the original
functions to confer resistance against structurally non-related molecules.
Among the biocide resistance strains intrinsic and acquired mechanisms are
described. Intrinsic resistance is an innate property conferred by the
bacterial genome (species-dependent) and includes impermeability, efflux, biofilms
and transformation of toxic compounds. To decrease the intercellular
concentration of noxious molecules, Gram-negative bacteria can regulate the
permeability of their membranes by decreasing the synthesis of porins (membrane
pore- forming proteins involved in antibiotic uptake) and modifying the
lipopolysaccharide structure (Poole et
al., 2002) or over expressing the efflux pumps (membrane portentous complexes
involved in antibiotic expulsion) (Poole 2007). These strategies are involved
in the resistance against antibiotics and biocides. In parallel, the acquired
resistance occurs via mutation and acquisition of mobile DNA (transposon,
plasmids) coding for resistant element (enzyme transporter).
Similarly,
the acquired processes may protect against antibiotics and biocides (Millard
2004). In addition, some of the mechanisms that play a major role in resistance
are controlled by diverse genetic cascade regulations that share common gene
regulations (Sox S, Mar A) (Poole 2007).
1.9 RESEARCH JUSTIFICATION
Several
research works have been carried out on assessment of antimicrobial activities but
very few have been documented on the efficacy of commercially available
household biocides and their impact on resistance drive in the environment and
homes. Hopefully, some botanicals may contain biocidial properties as they are
used traditionally for such purpose with little or no scientific background or
documentation for their activity. Thus,
this study seeks to access the antimicrobial efficacy of household biocides and
their resistance patterns as well some botanicals used as local biocides.
1.10 AIM AND OBJECTIVES OF THE STUDY
1.To
evaluate antimicrobial activities of commercial biocidal products and their resistance
pattern.
2.To
provide information to the public of the resistance pattern of microorganism to
biocide, through scientific presentation or publication
3.To
compare the effect of botanicals and biocides on selected pathogenic organisms.
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