ANTIBIOTIC SUSCEPTIBILITY PATTERN OF CLINICAL ISOLATES OF STAPHYLOCOCCUS AUREUS AGAINST THREE GROUPS OF ANTIBIOTICS

ABSTRACT

Infections caused by s.aureus is of public health concern due to the easy acquisition of resistance genes. In this research study, the antibiotic sensitivity pattern of clinical isolates of S. aureus in vitro was studied against 3 groups of antibiotics namely quinolones, cephalosporins and aminoglycosides, Susceptibility and resistance were compared and analysed using the disc diffusion method with forty clinical isolates of S.aureus from different specimens ranging from urine to wound and others from hospitals in umuahia. Quinolones were observed to have the greatest antibiotic activity on S. aureus in vitro. S.aureus was found to be most sensitive to pefloxacin (85%) followed by ciprofloxacin (80%). While cephalosporins showed 65% sensitivity, cefuroxin was observed to show 60%. The Aminoglycosides had reduced sensitivity than the other antibiotics used.

TABLE OF CONTENT

Title page                                                                                                                    i

Certification                                                                                                               ii

Declaration                                                                                                                 iii

Dedication                                                                                                                  iv

Acknowledgement                                                                                                      v

Table of Content                                                                                                         vi        

List of Table                                                                                                               ix

Abstract                                                                                                                      x

CHAPTER ONE: INTRODUCTION

1.1  BACKGROUND                                                                                            1

1.2 IMPORTANCE OF RESEARCH                                                                        3

1.3. THE AIM AND OBJECTIVE OF RESEARCH                                                 4

1.4 OBJECTIVE                                                                                                         4

CHAPTER TWO: LITERATURE REVIEW

2.0. THE STAPHYLOCOCCI                                                                                    6

2.1. IMPORTANT PROTERTIES OF STAPHYLOCOCCI                                     6

 2.2. STAPHYLOCOCCUS AUREUS                                                                         7

2.3. ROLE IN DISEASE                                                                                            8         

2.4. SKIN INFECTIONS                                                                                            8

2.5. BACTEREMIA.                                                                                                  9

 2.6. ANIMAL INFECTIONS                                                                                    9

2.7. VIRULENCE FACTORS                                                                                    10

2.8. STAPHYLOCOCCAL PIGMENTS                                                                   12

2.9. CLASSICAL DIAGNOSIS                                                                                 13

2.10. TREATMENT AND ANTIBIOTIC RESISTANCE                                        13

2.11. MECHANISM OF RESISTANCE                                                                   15

2.12. CARRIAGE OF STAPHYLOCOCCUS AUREUS                                            18

2.13. INFECTION CONTROL                                                                                  18

CHAPTER THREE: MATERIALS AND METHOD

3.1. SAMPLES                                                                                                           20

3.2. DISC DIFFUSION METHOD                                                                            20

CHAPTER FOUR: RESULT PRESENTATION

4.1       Results                                                                                                            21

CHAPTER FIVE

5.1 DISCUSSION                                                                                                       27

5.2 CONCLUSION                                                                                                     30

5.3 RECOMMENDATION                                                                                        30

Reference

Appendix

LIST OF TABLES

Title                                                                                                    Page

Table 1            Different Isolates and its sources                                                                    22

Table 2             Analytical results of comparative analysis of antibiotic sensitivity of

staphylococcus aureus on different groups of antibiotics.                                     23

Table 3            Antibiotic sensitivity and resistance pattern of staphylococcus

aureus from clinical isolates against Quinolones,

Cephalosporins and Aminoglycosides in percentage and number                        24

CHAPTER ONE

1.0  INTRODUCTION

1.1  BACKGROUND

Staphylocous aureus is a gram-positive bacterium belonging to the family staphylococaceae and is often found as a commensal on the skin, glands and mucous membrane particularly in the nose of healthy individuals (Plata et al., 2009). It is a vertical human pathogen causing infections ranging from relatively mold skin as well as toxin mediated syndromes such as toxic shock syndrome and food poisoning. It is also a causative agent for some sexually transmitted infection mostly found in men and women (Shittu et al., 2006).

Staphylococcus aureus is usually a harmless colonizer of about one third of healthy humans and is mostly likely found in nares. It mostly colonizes the anterior nares (nostrils). The rest of the respiratory tract, open wounds, intravenous catheters and urinary tract. Healthy individuals carry MRSA (Methicillin within resistant staphylococcus aureus) asymptomatically for periods ranging from a few weeks to many years. Patients with compromised immune systems are at significantly greater risk of symptomatic secondary infection. Nasal carriage of staphylococcus aureus has been closely associated with staphylococcal disease (Von Etiff, et al., 2001). Colonization increases the risks of subsequent infection since those with staphylococcus aureus infection are usually infected with their colonizing strain (Gordon and Lowry, 2008). Infection may occur when there is breach of the skin or mucosal barrier that allows the organism access to adjoining tissues or the blood strecum (Boucher et al., 2008). Also infections can be as a result of people been in crowded places where there is skin to skin contact, people with weak immune systems (HIV, AID, hipus or cancer suffers from transplant, diabetes, intravenous drugs) users of Quinolone antibiotics, people or students living in dormitories, women with frequent urinary tract infections or kidney infections due to infections in the bladder and animal or livestock handlers.

Staphylococcus aureus is able to cause a large diversely of both benign and lethal infections in humans and animals because of wide range of virulence factors that include various toxins and enzymes (Bal and Gould, 2005). It has reemerged as one of the most important human pathogens and has become a leading cause of hospital and community acquired infections (Shittu and Lin, 2006).

Prior to the introduction of penicillin for the treatment of staphylococcus aureus infections in the K4os, the mortality rate of individuals with staphylococcal infections was about 80% (Skinner and Keefer, 1941). However within two years of the introduction of penicillin to medical use, penicillin resistant strains were discovered. By 1960, about 80% of all staphylococcus aureus strains were found to be resistant to penicillin (Deurenberg and Stobberingh, 2008). Methicillin was introduced in 1959 to treat infections caused by penicillin resistant staphylococcus aureus (Enright et al., 2002) but by 1961 there were reports of methicillin resistant staphylococcus aureus from hospitals (Barrett et al., 1968).

Methicillin resistant staphylococcus aureus (MRSA) has become a leading cause of hospital-acquired infections worldwide accounting for more than 60% of staphylococcus aureus isolates in hospitals in the world (Baranovich et al., 2010). Established risk factors for hospital acquired methicillin resistant staphylococcus aureus (HA - MRSA) infection include recent hospitalization or surgery, residence in a long term care facility, dialysis and indwelling percutaneous medical devices and catherers (Naimi et al., 2003) causes of MRSA infections have been documented among healthy community dwelling persons without the establishment risk factors for MRSA infections. These infections are referred to as community acquired or community associated MRSA infections CA-MRSA. The emergency of CA-MRSA became a cause for concern because it differs from HA MRSA in that it does not generally belong to a major dorial groups of epidemic MRSA, is susceptible to most -Lactam antibiotics, contains the type IV staphylococcal cassette chromosome mec and frequently carries gene responsible for the production of phantom – valentine leukocidin (PVL) (David and Daun, 2010).

Vancomycin has been used in the treatment of infections caused by MRSA but there has been an emergence of vancomycin resistant staphylococci (Kirst et al., 2000). Two forms of staphylococcus aureus resistant to vancomycin have been identified. One form is the vancomycin intermediate resistant staphylococcus aureus (VISA) and the other form is the vancomycin resistant staphylococcus aureus (VRSA).

The determination of the different anti-biotypes of staphylococcus aureus helps in monitoring the antibiotic resistant profile trends which in turn aids in the correct implementation of antibiotic regimens for staphylococcus aureus infections.

1.2 IMPORTANCE OF RESEARCH

Many studies have characterized staphylococcus aureus and MRSA isolates from hospitals and countries and have identified strains that appear to be well adapted to the hospital environment, are established in several hospitals within a country, or have spread internationally as epidemic MRSA, EMRSA (Enright et al., 2002). This has allowed a better understanding of the evolution of both staphylococcus aureus and methicillin resistant staphylococcus aureus over time and the ability to compare the genetic variation in different geographic locations. Such studies is important in finding out the most activate and effective drug that can be used for the treatment of both hospital acquired infections or otherwise. This is due to the increase in resistance i.e. antibiotic resistance of staphylococcus aureus in the world. The increase in both methicillin resistant staphylococcus aureus and other resistance has led to reason for this research work. The mechanisms for the emergence and spread of staphylococcus aureus clones in Africa are poorly understood. Therefore the characterization of isolates may provide baseline information needed in establishing effective infection control measures and effective treatment. In Nigeria, information on the resistance trends of staphylococcus aureus and MRSA both in health care settings and in the community is limited. Also, there is inadequate information on virulent strains. Therefore, this study is channeled in knowing the antibiotics which these different strains of staphylococcus aureus are resistant to and why. And also how to combine drugs from different groups of antibiotics and be used for treatment of staphylococcus aureus infection in Nigeria and the world at large.

1.3. THE AIM AND OBJECTIVE OF RESEARCH

The aim of this study is to determine the differences in vitro antibiotics sensitivity pattern of three different groups of antibiotics

1.4 OBJECTIVE

i.               To determine the antibiotic susceptibility pattern of staphylococcus aureus strains isolated from clinical sources.

ii.              To investigate the susceptibility pattern of the different groups of (cephalosporins, quinolones, aminoglycosides and macrolides) antibiotics against staphylococcus aureus.

iii.            To compare the most active  antibiotics in vitro on staphylococcus aureus in vitro.

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