ISOLATION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS FROM THE NOSTRILS OF STUDENTS OF MICHAEL OKPARA UNIVERSITY OF AGRICULTURE, UMUDIKE

ABSTRACT

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved as a major health care-acquired pathogen worldwide into one that can be found in the community. This study was carried out to determine the carriage rate of MRSA in the nostrils of students of Michael Okpara University of Agriculture, Umudike. Of the 100 samples analysed, 65(65 of 100) were positive for S. aureus, Some of the S. aureus isolates that showed resistance to many antimicrobial agents were found to be methicillin-resistant. The prevalence of MRSA nasal carriage was 9.2% (6 of 65) detected by oxacillin disk diffusion methods. MRSA was identified in 3.1% (2 of 65) of males and 6.1% (4 of 65) of females. All the MRSA isolates showed multi-drug resistance to at least four antibiotics tested. However, MRSA strains were highly sensitive to Levofloxacin. The highest rates of resistance were observed for Amoxicillin and Ampicillin.

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgements iv

Table of Contents v

List of Tables and Figures viii

Abstract ix

CHAPTER ONE

Introduction

1.1 Introduction 1

1.2 Aim and Objectives 3

CHAPTER TWO

Literature review

2.1 Staphylococcus aureus 4

2.1.1 Pathogenesis of S. aureus 4

2.1.2 Mode of transmission of S. aureus 5

2.1.3 The role of nasal carriage of S.aureus in Staphylococcus aureus

Infections 6

2.1.4 Virulence factors in S. aureus 6

2.1.5 Mode of reproduction of S. aureus 8

2.1.6 Antibiotic susceptibility and resistance of S. aureus 9

2.2 Methicillin-resistant Staphylococcus aureus 10

2.2.1 Hospital-acquired and Community-Acquired MRSA 11

2.2.2 Clinical implications of MRSA 12

2.2.3 Mechanism of methicillin resistance 12

2.2.4 Mode of transmission 13

2.2.5 Risk factors for CA-MRSA 13

2.2.6 Prevention and control of CA-MRSA 15

CHAPTER THREE

Materials and methods

3.1 Study Location and design 16\

3.2 Sample collection 16

3.3 Sterilization of materials 16

3.4 Preparation of culture media 17

3.5 Inoculation of the nasal sample 17

3.6 Identification of Staphylococcus aureus 17

3.7 Preparation of turbidity standard equivalent to McFarland 0.5 18

3.8 Antibiotic Susceptibility test 19

3.9 Detection of methicillin resistance 19

CHAPTER FOUR

Results 20

CHAPTER FIVE

Discussion, Conclusion and Recommendation

5.1 Discussion 29

5.2 Conclusion 30

5.3 Recommendation 31

REFERENCES

APPENDIX

LIST OF TABLES AND FIGURES

CHAPTER ONE

INTRODUCTION

1.1 INTRODUCTION

Staphylococcus aureus (S. aureus) is a microorganism that colonizes the skin and mucosal surfaces of healthy individuals, but it is also one of the most common causes of community-acquired and hospital infections. The bacteria can cause infections of all tissues and organs, starting from superficial skin infections, to severe, life-threatening infections, such as bacteriemia and sepsis. S. aureus causes invasive infections mostly in immunocompromised and hospitalized patients (Wertheim et al., 2005).

In healthy individuals, S. aureus can colonize the skin and mucosa of any part of the body, with the anterior nares being the most commonly colonized site. The anterior nares have been shown to be the main reservoir of S. aureus in both adults and children (Pathak et al., 2010). Nasal carriage of S. aureus represents a major risk factor for the development of infection with this bacterium. The S. aureus is transmitted to nares by contaminated hands and from surfaces where it can survive for months. (Kluytmans et al., 1997; Pathak et al., 2010). Nasal carriage of S. aureus acts as endogenous reservoir for clinical infections in the colonized individual but also as a source of cross-colonization for community spread (Pathak et al., 2010). The spread of colonization occur especially in close contact areas like schools, pre-schools or households (Peacock et al., 2003), probably by the contaminated hands and surfaces. (Pathak et al., 2010).

Emergence of antibiotic resistant forms of pathogenic S. aureus is a worldwide problem in clinical medicine (Klutymans et al., 1997). Pathak et al., 2010 stated that nasal colonization with S. aureus plays pivotal role in the increasing prevalence of resistant community acquired S. aureus infections worldwide. Bacterial resistance to antibiotics has been recognized since the first drugs were introduced for clinical use. Penicillin was first introduced in 1941, when less than 1% of Staphylococcus aureus strains were resistant to its action. By 1947, 38% of hospital strains had acquired resistance and currently over 90% of Staphylococcus aureus isolates are resistant to penicillin. (Power, 1998). Methicillin which is a penicillinase - resistant semisynthetic penicillin, was then introduced into human medicine to treat penicillin- resistant staphylococci. However, some strains soon gained resistance, hence resistant strains were termed ‘Methicillin-resistant Staphylococcus aureus’ (MRSA) (Brown et al., 2005).

Methicillin- resistant S. aureus (MRSA) was first discovered in 1961; they are isolates of S. aureus which have acquired genes encoding antibiotic resistance to all penicillins including methicillin and other narrow spectrum β lactamase resistant penicillin antibiotics (Foster, 1996). MRSA is an established pathogen in most health care facilities. Previously limited to hospitals, MRSA infections have been increasingly reported in the community (Naimi et al., 2003; Mainous et al., 2006). The reservoir of MRSA is infected and colonized patients (Thompson et al., 1982). Methicillin-resistant S. aureus (MRSA) has acquired the ability to survive in the presence of beta-lactam antibiotics, including penicillin, methicillin, and cephalosporins. (Malachowa and Deleo, 2010). This is because of a mecA gene complex which also allows cross resistance to non-beta-lactam antibiotics such as erythromycin, clindamycin, gentamicin, cotrimoxazole and ciprofloxacin due to the presence of insertion sites for plasmids and transposons (Chambers, 2001).

MRSA infections can be classified into two major groups: Hospital-acquired MRSA (HA-MRSA) and Community-acquired MRSA (CA-MRSA). HA-MRSA is responsible for post-operative wound infections, or infections resulting from implanted devices such as catheters, that are acquired within the healthcare setting. Typically, patients infected with HA-MRSA are immune-compromised and the resulting infections are generally more invasive. CA-MRSA typically manifests itself as skin infections, such as pimples or boils, and is classified as being acquired outside of any type of healthcare setting. These infections are typically more serious than minor skin irritation and affect otherwise healthy individuals (Raygada and Levine, 2009). The most common community- acquired infections are skin and soft tissue infections (Wertheim et al., 2005). Community-associated MRSA first appeared in high-risk populations such as intravenous drug users, people in nursing homes, and people who were chronically ill, but they are now reported even in healthy children. Until recently, these strains were susceptible to many antibiotics other than beta-lactams; however, resistance seems to be increasing, and multiple antibiotic resistant strains have started to emerge. (Tenover and Goering, 2009)

Carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection (Kluytmans et al., 1997). Thus, decolonization of the nares may prevent S. aureus infections and the attendant complications (Herwaldt, 1998). A regular surveillance system is important in ensuring quality of care (Pathak et al., 2010). Therefore, the need for this study to determine its prevalence among the students.

1.2 AIM AND OBJECTIVES

Aim

i. To evaluate the Methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage among the students in the university.

Objectives

i. To isolate and identify S. aureus from the nostrils of students.

ii. To determine the antibiotic susceptibility profile of the S. aureus isolates.

iii. To determine the prevalence of Methicillin resistance among the isolates.

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