ABSTRACT
Staphylococcus aureus is an important human pathogen that causes serious infections both in hospitals and communities globally due to its multi-drug resistance tendency. This study was undertaken to determine the prevalence of Staphylococcus aureus and antibiotic sensitivity pattern among pigs and pig farmers in Michael Okpara University of Agriculture, Umudike (MOUAU). Sixty (60) swab samples were collected from various sites of the pigs of 2 species (Duroc and Large-white) and from the nostrils of the pig farmers. The samples were subjected to standard microbiological techniques to identify Staphylococcus aureus. Resistance to Methicillin was determined by using Cefoxitin (30µg). A total of 48 isolates of Staphylococcus species were recovered representing 80% (48/60) of total isolates and MRSA carriage of 0% (0/48) was obtained showing no prevalence of MRSA. Large white specie of the pigs had a higher prevalence of 70.83% (34/48) compared with the isolates from Duroc pigs which had a lower prevalence of 29.16% (14/48). The antibiotic susceptibility profiles of the isolates to the commonly used drugs showed high resistance to Ceftazidime (95.83%) followed by Erythromycin (47.90%). All isolates were susceptible to Cefuroxime (100%), Ceftriaxone (100%) and Cefoxitin (100%). The prevalence of Staphylococcus aureus was more in the nasal discharge of the pigs (61.54%) than in the pig farmers (38.46%). This should therefore call for urgent intervention because pigs can serve as reservoir through which infections related to Staphylococcus aureus can spread to other animals, humans and community at large. Therefore, proper hygiene practices, control of indiscriminate use of antibiotics, and frequent screening of this population for Staphylococcus aureus related infections, are hereby recommended both for prevention and control of livestock acquired Staphylococcus aureus infections.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgment iv
Table of contents v
Abstract ix
CHAPTER ONE
1.0
INTRODUCTION 1
1.1 Aims and objectives of the study 3
CHAPTER TWO
2.0
LITERATURE REVIEW 4
2.1 Staphylococcaceae 4
v
2.2 Staphylococcus
aureus 5
2.3 Morphology and identification of Staphylococcus aureus 5
2.4 Biology and pathogenesis of Staphylococcus aureus 6
2.5 Methicillin Resistant Staphylococcus aureus (MRSA) 7
2.6 Mechanism of resistance of MRSA 9
2.7 Historical Background of Methicillin
Resistant Staphylococcus aureus (MRSA) 10
2.8 Epidemiology of MRSA 11
2.9 MRSA and its association with Pigs 12
2.10 Antibiotics 12
2.10.1 Classes
of Antibiotics 13
2.10.2 β-Lactam Antibiotics 13
2.11 Penicillin 14
2.12 Methicillin 15
2.13 Mode of action of β-Lactam Antibiotics 16
2.14 Mechanism of resistance of β-Lactam
antibiotics 17
vi
CHAPTER THREE
3.0
MATERIALS AND METHODS 18
3.1.1 Culture media 18
3.1.2 Reagents used 18
3.1.3 Equipment and materials used 18
3.1.4 Antibiotic discs used 18
3.2 Collection of samples 18
3.3 Media preparation 19
3.4 Characterization and identification of the
isolates 19
3.4.1 Growth on Mannitol Salt Agar (MSA) 19
3.4.2 Growth on blood agar (Sub-culturing of the
isolates) 20
3.4.3 Identification of Staphylococcus aureus 20
3.5 Gram staining 20
3.6 Biochemical characterization of isolates 21
3.6.1 Catalase Test 21
3.6.2 Coagulase Test 21
vii
3.7 Antibiotic Sensitivity Testing 22
3.8 Detection of MRSA (using disc diffusion
method) 22
CHAPTER FOUR
RESULTS 23
CHAPTER FIVE
5.0 DISCUSSION AND
CONCLUSION 32
5.1
Discussion 32
5.2
Conclusion 33
References 35
CHAPTER
ONE
1.0 INRODUCTION
Staphylococcus aureus
is a well-known food-borne pathogen that produces heat-stable enterotoxin
during growth on varieties of food, including meat (especially pork) and
poultry product, eggs, cream filled pasteries, potatoes and some salad (Cefai et al; 2010). It is a bacterium of
significant importance because of its ability to cause a wide range of disease
and capacity to adapt to diverse environmental forms (Aarestrup et al., 2010). The organism colonies
skin, skin glands and mucous membrane, causing infections both in human and
animals such as rashes, inflammations of bones and the meninges as well as
septicaemia (Adjitev et al; 2013). In
addition, Staphylococcus aureus
causes inflammation of the mammary gland in bovine and the lower part of the
foot in poultry (Burke et al; 2000).
Penicillin and its derivatives, including methicillin have been used for the
treatment of infections caused by Staphylococcus
aureus (Cavaco LM et al., 2014).
However, certain strains of Staphylococcus
aureus are resistant to most penicillin derivatives (Cosgrove et al., 2003) and ordinary antimicrobial
agents like drugs from the family of aminoglycosides, macrolides,
chloramphenicol, tetracycline and fluroquinolone (Cuny et al., 2010).The development of antibiotic resistance has become a
global public health challenge which is causing ineffectiveness of
antibacterial agents leading to increase in diseases and death rate (Dam-Deisz
WD et al., 2009).
Over the last 50 years Methicillin resistant Staphylococcus aureus (MRSA) has emerged
as a major public health issue in both community and nosocomial infections. It
has become one of the leading nosocomial pathogen and recently has been
responsible for life threatening infections. In the past few decades,
resistance towards methicillin by MRSA has been accompanied by resistance
towards wide range of other antibiotics such as gentamycin, erythromycin, and
tetracycline (Dand MZ et al., 2010).
The wide use of antibiotics in the
treatment of bacterial infections has led to the emergence and spread of
resistant strains. Methicillin resistant Staphylococcus
aureus (MRSA) is a major cause of infections in farm animals especially
pigs. MRSA infections are very difficult to cure because MRSA strains are
resistance against almost all clinically available antibiotics. For most MRSA
strains, glycopeptide-type drugs such as Vancomycin are the only effective
antimicrobial agents. However, Vancomycin resistant Staphylococcus aureus (VRSA) has been reported (Deresnski, 2005). According
to Ekklenkamp et al. (2006), it is
extremely important to find new antimicrobial agents or new ways that are
effective for the treatment of infectious diseases caused by drug-resistant bacteria
including MRSA.
A gene known as MecA is responsible for
the protein resistance to methicilin which codes for penicillin-binding protein
PBA2A (Etebu et al; 2016). Lately, a
new methicillin resistant gene, MecC was described in Staphylococcus aureus (Gibs ST et
al., 2006). Graham, D et al (2009),
Gravel H et al; (2011) reported MRSA isolates carrying MecC gene from humans
and animals Haddadin et al (2012) suggested the public health hazard of MecC positive
MRSA isolates as it has been isolated in human case and livestock (especially
pigs). Reports of MRSA isolated in pigs seems to be rising in number (Hartmeyer
et al., 1997; Tomlin et al; 1999; Rich and Robert, 2004). The epidemiology of MRSA isolates from human
and animals sources showed that for certain strains; a cross-infection might
have happen (Heedeick D et al; 2011 Ike
et al; 2016; Kar et al; 2016).
Studies conducted by Khana T et al; (2008) and animals can be potential source
of MRSA infection to human. Therefore, knowledge on the epidemiology of MRSA
will underpin effective and control strategies including the rational use of
antibiotics.
Resistance to penicillins and other
β-lactams is due to one of four general mechanisms like; inactivation of
antibiotic by β-lactamase, modification of target PBPs, impaired penetration of
drug to target PBPs and efflux. β-lactamase production is the most common
mechanism of resistance. β-lactamases produced by Staphylococcus aureus, Haemophilus
species. and Escherichia coli are
relatively narrow in substrate specificity preferring penicillins to
cephalosporins. Altered target PBPs are the basis of methicillin resistance in
Staphylococcci and of penicillin resistance in pneumococci and Enterococci.
These resistant organisms produce PBPs that have low affinity for binding
β-lactam antibiotics; consequently they are not inhibited except at relatively
high drug concentrations (Van Cleef et al.,
2010).
1.3 Aims and Objectives of the Study
This
aim and objective of this study is:
1. To
isolate and identify Staphylococcus
aureus and determine its prevalence as well as its antibiogram in pigs and
pig farmers of Michael Okpara University of Agriculture, Umudike (MOUAU).
2. To
determine the level of Methicillin resistance in MOUAU pig farm.
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