ANTIBIOGRAM OF ESCHERICHIA COLI AND SALMONELLA SPP. CAUSING GASTROENTERITIS IN PATIENTS IN UMUAHIA

ABSTRACT

Food safety and quality is a global topic of public concern. Salmonella and Escherichia coli are zoonotic enterobacteria which are responsible for outbreaks of both human and animal diseases called Gastroenteritis. The aim of the study was to determine the antibiogram of Salmonella spp and Escherichia coli causing gastroenteritis in patients. A total of 50 stool samples were collected from different hospitals and Laboratories and analyzed for in this research. Stool samples were cultured within 4 hours of collection. About one gram of stool sample was suspended in sterile nutrient broth and incubated at 370C for 24 hours. The concentrated isolates from the nutrient broth were then used to inoculate MacConkey and Salmonella-Shigella agar plates and incubated at 370C for 24 hours. Colonies that showed typical characteristics of E. coli morphology were subcultured into Eosin-Methylene blue agar and incubated at 370C for 24 hours. Out of the 50 watery stool samples collected, 22(44%) and 28(56%) were obtained from male and female respondents respectively. Frequency of occurrence of the isolates showed that a total of 59 organisms were isolated, E. coli and Salmonella spp had a frequency occurrence of 71.2% and 28.8% respectively. E. coli and Salmonella spp were subjected to several antibiotics drugs. The organisms exhibited multiple resistance to the antibiotics tested, E. coli and Salmonella species both showed highest and least susceptibility to Ceftriazone and Cotrimoxazole respectively. It could be recommended from this study that Ceftriazone, Ciprofloxacin and Gentamicin be used since they are more effective against the E. coli and Salmonella isolates in preference to Co-trimoxazole, Erythromycin, Amoxicillin and Chloramphenicol. Interventions, such as face-to-face counseling, encouraging  exclusive breastfeeding and vitamin A supplementation, Promotion of hand washing with soap, Improved water supply quantity and quality, including treatment and safe storage of household water and Community-wide sanitation to be promoted.

TABLE OF CONTENTS

Title Page                                                                                                                    i

Certification                                                                                                                ii

Dedication                                                                                                                  iii

Acknowledgements                                                                                                    iv

Table of contents                                                                                                        v

Lists of Tables                                                                                                             vii

Abstract                                                                                                                      viii

CHAPTER ONE

1.0       Introduction                                                                                                    1

1.1       Aim                                                                                                                 3

1.2       Objectives                                                                                                       3

CHAPTER TWO

2.0       Literature Review                                                                                           4

2.1       Escherichia coli                                                                                               4

2.1.1    Microbiology of Escherichia coli                                                                    4

2.1.2    Classification of Escherichia coli strains causing enteric infection                4

2.1.2.1 EnterotoxigenicE. coli (ETEC)                                                                       4

2.1.2.2 EnteropathogenicE. coli (EPEC)                                                                    4

2.1.2.3 EnteropathogenicE. coli (EIEC)                                                                     4

2.1.2.4 EnteroaggregativeE. coli (EAEC)                                                                  5

2.1.2.5 EnterohaemorrhagicE. coli (EHEC)                                                               5

2.1.3    Structure of Escherichia coli                                                                          6

2.1.4    Biochemical characteristics of Escherichia coli                                              6

2.1.5    Transmission of Escherichia coli                                                                    7

2.1.6    Clinical manifestation                                                                                     7

2.1.7    Laboratory diagnosis of Escherichia coli  O157                                            8

2.1.8    Treatment of Escherichia coli O157 infections in humans                             9

2.1.9    Prevention and Control of Escherichia coli O157 in humans            9

2.1.10 Prevention and control in animals                                                                   10

2.2       Salmonella Species                                                                                         12

2.2.1    Microbiology of Salmonella                                                                           12

2.2.2    Prevalence of Salmonella species                                                                   12

2.2.3    Transmission                                                                                                   13

2.2.4    Human Salmonella infections                                                                         13

2.2.5    Clinical manifestations of Salmonellosis in man and animal                          14

2.2.6    Laboratory diagnosis                                                                                      14

2.2.7    Serological Identification                                                                               15

2.2.8    Human Salmonella Infections                                                                        16

2.2.8    Treatment of Salmonella                                                                                 16

2.2.9    Prevention and control                                                                                    17

2.3       Enterotoxygenicity of E.coliO157 and Salmonella species                            18

2.3.1    Enterotoxins                                                                                                    18

2.3.2    Mechanism of action of LT and ST enterotoxins                                           18

2.3.3    Laboratory detection of enterotoxin production                                            19

2.4       Antibacterial agents                                                                                        20

2.4.1    Mechanism of action of antibiotics                                                                 20

2.4.2    Antibiotic resistance                                                                                       21

2.4.3    Mechanisms of antibiotic resistance                                                               22

2.4.3.1 Target alteration                                                                                              22

2.4.3.2 Cell wall impermeability                                                                                 23

2.4.3.3 Enzymatic modification or destruction                                                          23

2.4.3.4 Active efflux from the cell                                                                             24

2.4.4    Genetic Basis and Spread of Antimicrobial Resistance                                 24

CHAPTER THREE

3.0       Materials and Methods                                                                                   26

3.1       Materials                                                                                                         26

3.1.1    Culture media                                                                                                 26

3.1.2    Reagents and diagnostics                                                                               26

3.1.3    Equipment                                                                                                       26

3.1.4    Antibiotic discs                                                                                               26

3.2       Methods                                                                                                          27

3.2.1    Study area and dynamics                                                                                27

3.2.2    Sample collection and treatment                                                                     27

3.2.3    Identification and characterization of isolates                                                28

3.2.3.1 Gram staining                                                                                                  28

3.2.3.2 Motility test                                                                                                    28

3.2.3.3 Biochemical tests                                                                                            29

3.2.3.3.1 Urease test                                                                                                   29

3.2.3.3.2  Indole test                                                                                                   29

3.2.3.3.3  Methyl ted-vogesproskauer test                                                                  29

3.2.3.3.4  Citrate utilization test                                                                                 30

3.2.3.3.5  Triple sugar iron agar                                                                                  30

3.2.3.3.6 Eijkmann test                                                                                               30

3.2.4    Antibacterial susceptibility testing                                                                  31

CHAPTER FOUR

4.0   Results                                                                                                                32

CHAPTER FIVE

5.0       Discussion, Conclusion and Recommendation                                               39

5.1       Discussion                                                                                                       39

5.2       Conclusion                                                                                                      41

5.3       Recommendation                                                                                            41

References                                                                                                      42

LIST OF TABLES

Table                                      Title                                                                            Page

4.1:                  Source of samples                                                                               33

4.2:                  Age bracket of respondents                                                                34

4.3:                  Gram and biochemical characterization of isolates                             35

4.4:                  Frequency of occurrence of isolates                                                   36

4.5:                  Antibiotic susceptibility pattern of E. coli                                          37

4.6:                  Antibiotic susceptibility pattern of Salmonella species                      38

CHAPTER ONE

1.0 Introduction

Food safety and quality is a global topic of public concern. Salmonella and Escherichia coli are zoonotic enterobacteria that are responsible for outbreaks of both human and animal diseases called Gastroenteritis and have important health significance worldwide, with several transmission routes of which majority of human infections are being derived from the consumption of contaminated foods such as insufficiently cooked meat or improperly pasteurized milk and milk products (Jackson etal., 2007).

Gastroenteritis is of significant public health concern, because humans and animals can become infected from consumption of food/feed and drinking water contaminated with Salmonella and Escherichia coli spp. from feaces of infected animals and raw milk products which have not been adequately pasteurized (Jackson et al., 2007).

Gastroenteritis-causing pathogens are the second leading cause of morbidity and mortality worldwide. The organisms responsible are rotaviruses, Norwalk-like viruses, enterotoxigenic Escherichia coli (ETEC), Campylobacter jejuni and Clostridium difficile, Shigella spp., Salmonella and Escherichia coli spp., Cryptosporidium spp. and Giardia lamblia. These organisms are readily transmitted via food, water, environmental contacts, pets and from person to person, with morbidity rates in developing countries 3-to-6-fold higher than in developed countries (Acha et al.,2003)

Salmonella spp and Escherichia coli are important cause of bacterial contamination of the environment and the food chain (Ponce et al., 2008), and are the leading causes of acute gastroenteritis in several countries. In developing countries, contaminated vegetables, water and human-to-human transmission are believed to contribute to comparatively larger proportion of human cases than those in industrialized countries (Acha  et al.,, 2003).

Salmonella and Escherichia coli have been associated with documented food-borne illness episodes in the past 20 to 30 years and their numbers appear to be increasing (Fratamico et al., 2005).

Acquired antibiotic resistance is a growing worldwide problem due to abusive use of antibiotics in humans, animals and agriculture. Food contamination with antibiotic resistant bacteria can be a major threat to public health, as the antibiotic resistant determinant can be transferred to other bacteria of human significance. This is in view of the fact that the prevalence of antibiotic resistance among food borne pathogens has increased during past decades (Van et al., 2007).

The global problem of antimicrobial resistance is particularly pressing in developing countries with reservoirs of resistance present in healthy human and animal populations and also the increasing resistance to flouroquinolones by Salmonella and Escherichia coli spp as reported in Lagos, which is of public health concern. Antimicrobial resistance has complicated the selection of antibiotics for the treatment of enteric bacterial pathogens, particularly to commonly used antimicrobial agents such as ampicillin, tetracycline and trimethoprim–sulfamethoxazole(Van et al., 2007).

Antibiograms give information that can be used to raise awareness of resistance problems, support the use of optimal empiric treatment, and identify opportunities to reduce inappropriate antibiotic usage and to discover success of such efforts (Fridkin et al., 2001).

A typical antibiogram displays the total number of bacterial isolates tested against a range of antimicrobials and includes the percentage of bacterial isolates susceptible or resistant to each antimicrobial agent tested (Fridkin et al., 2001).

1.1 Aim

The aim of this study is to determine the  antibiogram profiles of Salmonellaspp and Escherichia coli species causing gastroenteritis in patients in umuahia.

1.2 Objectives

The specific objectives of the study are to:

1.      Isolate and identify Salmonella spp and Escherichia coli  causing gastroenteritis among patients in Umuahia.

2.       Determine the prevalence of Salmonella spp and Escherichia coli  causing gastroenteritis in patients in Umuahia.

3.      Determine the antimicrobial resistance patterns of Salmonella  spp and Escherichia coli 

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