OCCURRENCE AND ANTIMICROBIAL RESISTANCE PATTERN OF SPECIES OF SALMONELLA ASSOCIATED WITH HANKED CARROT TUBERS

ABSTRACT

Salmonella is among the most important foodborne pathogens worldwide with fresh vegetables as major route of transmission to man. A total of 12 samples of carrot samples were analyzed for the presence of Salmonella species using standard plating techniques on Salmonella Shigella agar. Samples were cultured using selective isolation with prior enrichment method. Presumptive isolates were identified and characterized using conventional biochemical methods. These bacteria species were tested for their susceptibility to standard antibiotics by agar disk diffusion method. Mean bacterial load of the carrot samples was 7.47logcfu/g for samples obtained at Orieugba Market; 7.13logcfu/g at Isigate Market and 7.27logcfu/g for Ndioru market. Similarly, the coliform counts were 4.93logcfu/g, 2.83logcfu/g and 3.50logcfu/g for Orieugba Market, Isigate Market and Ndioru markets respectively. All Salmonella isolates (100%) were resistant to Augmentin. high resistance percentage was observed against nitrofurantoin (45.5%), cefuroxime (72.7%), cefotaxime (72.7%), for the Salmonella isolates. Eight out of the eleven (72.7%) Salmonella isolates in this study were susceptible to Gentamicin while 18.2% of the Salmonella isolates were resistant to ofloxacin. The emergence of high antimicrobial resistance among Salmonella isolates is alarming since these vegetables are commonly eaten raw and has obvious implications for public health because multidrug resistance limits the possible effectiveness of therapeutic treatments. This study provides data that support the potential transmission strains of Salmonella harboring resistance factors from vegetables and environmental sources to cause infections in humans.

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 Aims and Objectives

CHAPTER TWO

2.1 Literature Review

2.2 Carrot (Daucuscarota)

2.3 The Genus Salmonella

2.3.1 Salmonella and Processed foods

2.3.2 Epidemiology for non-typhoid Salmonella infections

2.4 Preventing Food Spoilage 

2.4.1 Pre-harvest and Harvest Factors

2.4.2 Decontamination of vegetables

2.5    Antibiotic Resistance

CHAPTER THREE

3.0       Materials and Methods

3.1       Sample Collection

3.2       Culture Media preparation

3.3       Preparation of samples

3.3.1    For the Isolation of Salmonella Species

3.4       Gram Staining

3.5       Biochemical Tests

3.5.1    Catalase Test

3.5.2    Indole Test

3.5.3    Citrate Utilization Test

3.5.4    Hydrogen Sulphide (H₂S) Production Test

3.6       Antibiotics Sensitivity Test

3.7       Stress Tolerance Assay

CHAPTER FOUR

4.0       Results                                                                                                                                   

CHAPTER FIVE

5.0       Discussion, Conclusion and Recommendation                                                                     

5.1       Discussion                                                                                                                  

5.2       Conclusion                                                                                                                 

5.3       Recommendation                                                                                                      

References                                                                                                                             

LIST OF TABLES

Table                           Title                                                    Page

4.1:                              Mean Bacterial Load of Carrot Samples

4.2:                  Morphological and Biochemical Characterization of the Isolates

4.3:                              Antibiotics Resistance Pattern for each Isolate.

4.4:                  Antimicrobial Susceptibility Pattern of the Salmonella isolates

4.5:                              Survival of the resistant isolates to stress conditions

CHAPTER ONE

1.0      INTRODUCTION

Fresh fruits and vegetables promote good health but harbour a wide range of microbial contaminants. Differences in microbial profiles of various fruits and vegetables result largely from unrelated factors such as resident microflora in the soil, application of nonresident microflora through animal manures, sewage or irrigation water, transportation and handling by individual retailers (Ray and Bhunia, 2007; Ofor et al., 2009). In developing countries such as Nigeria, continued use of untreated waste water and manure as fertilizers for the production of fruits and vegetables is a major contributing factor to contaminations.

Food borne outbreaks associated with vegetables that are partially processed or consumed naturally have increased over the years (Beuchat, 2002). This rise in the food-borne outbreaks from vegetables is due to the favorable conditions that the vegetables provide consequently encouraging the growth and survival of many types of microorganisms. Some of the favorable conditions include nutrient rich internal tissues-comprising polysaccharides (starch), pectin, hemicelluloses and cellulose. Enteropathogens such as Escherichia coli and Salmonella are among the greatest concerns with food-borne outbreaks. In 2007, these organisms were implicated in food-borne outbreaks in UK that resulted in the recalling of bagged lettuce (Heaton and Jones, 2008). Such recalls damage the consumerʼs confidence and hampers economically the income and corporate image of such vegetable crop.

Salmonella is one of the most important genera of pathogenic bacteria implicated in foodborne bacterial out-breaks and disease. Salmonella infections are a significant public health problem in many parts of the world. According to Erdem et al. (2005), more than one million human illnesses can be attributed to this pathogen each year. Salmonella can be transmitted in several ways, but the majority of human infections are the result of consumption of contaminated foods. An estimated 95% of these infections are associated with food (Hernandez et al., 2005).

Fresh and minimally processed vegetables and fruits provide the most important human diet that contains carbohydrates, proteins, vitamins, minerals, and fiber. Their role in reducing the risk of lifestyle associated illnesses such as heart disease, diabetes, and cancer has resulted in a further increase in desirability and consumption.

For instance, Food and Drug Administration (FDA) and World Health Organization (WHO) have recommended 5–9 servings of fruits and vegetables to be taken daily because correct fresh produceintakealonecouldsave2.7millionlivesayear (WHO, 2013).

In contrast to their health benefits, the consumption of fresh fruits and vegetables has also been associated to risk for consumers (Adabara et al., 2012). Outbreaks of food infections associated with consumption of ready-to-eat vegetables have been increasing (Adabara et al., 2012). Several outbreaks of illness caused by bacteria, viruses, and parasites have been linked epidemiologically to the consumption of a wide range of vegetables. Furthermore, surveillance of vegetables has indicated that these foods can be contaminated with various bacterial pathogens, including Salmonella spp., Shigella spp., Shiga toxigenic E. coli (STEC), Listeria monocytogenes, and Campylobacter spp. (Nillian et al., 2011).

The enteropathogens Escherichia coli and Salmonella have been implicated in cases of diarrhea and typhoid fever following consumption of contaminated vegetables (Salleh et

al., 2003; Pui et al., 2011; Diana et al., 2012). In most developing countries, street vending of fresh vegetables are on the increase and as such precautionary measures on the safety of the vegetables are not considered. Consequently, such vegetables could be a repository for various organisms that can severely affect the welfare of the consumers, shelf-life and nutritional worth of the vegetables.

Salmonella is an enteric bacterial pathogen and a major pathogenic bacterium that causes food poisoning. Its routes of infection include contaminated foods and water.  Salmonella species are leading causes of acute gastroenteritis in several countries and salmonellosis remains an important public health problem worldwide, particularly in the developing countries (Rotimi et al., 2008). Developing countries are more concerned by a broad range of these diseases among which appears cholera, campylobacteriosis, infections with Escherichia coli, shigellosis, brucellosis, hepatitis A and salmonellosis. In this numerous of foodborne infections, salmonellosis is the most frequent infection with a great number of serotypes and intoxications caused with lethality in 1% cases (Ao et al., 2015; Assi-Claire, 2000). Among the most foodborne infections with Salmonella, the lettuce takes up a significant place. According to Petterson et al. (2010), the consumption of the fruit and vegetables constitutes a factor of potential risk of infection by bacteria enteropathogens such as Salmonella and Escherichia coliO157. Cases of food poisoning related to the contaminated vegetable ingestion were identified a little everywhere in the world (Wendelet al., 2009).  Among the factors generally implicated in the contamination of vegetables appears the irrigation water (Koffi-Nevry et al., 2011).

Drug resistance among Salmonella strains has emerged worldwide, making antimicrobial susceptibility testing an important role in public health laboratories. Antibacterial agents are often recommended for the treatment of suspected salmonellosis. These can enhance the antibiotics resistances genes. Human-to-human transmission of S. enteric serovar Typhimurium makes this a pathogen of global concern.

Controlling Salmonella infection could be challenging due to its high tolerance to environmental stresses, widespread distribution, multiple drug resistance, and adaptability (Chen et al., 2013). Excessive and improper uses of antibiotics are the main factor attributed to increasing of antibiotic resistant bacteria. The antibiotic resistant bacteria will survive and continue to multiply through several mechanisms which allow them to survive antibiotic treatments. There is potential for the normal faecal flora of humans to be augmented by antibiotic resistant strains of bacteria acquired in the course of eating fresh uncooked vegetable salads. Periodic surveillance to determine the prevalence and quantity of Salmonella spp. in food is important to control human salmonellosis. Monitoring the use of antimicrobial agents and the emergence of resistant strains in food products destined for human consumption is a risk management option that can prevent the development and spread of antimicrobial resistance in microorganisms.

1.1       Aims and Objectives

1.     To determine the total bacterial load of carrot samples

2.     To determine the occurrence of Salmonella spp. in carrot samples

3.     To determine the antibiotic resistance profiles of Salmonella isolated from these samples

4.     To determine the response of the salmonella isolates to different stress conditions.

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