ABSTRACT

Microbiological evaluation of vended ready to eat fruits was conducted within Umudike environs. Pre-cut fruit samples comprising watermelon, garden eggs, pineapple and pawpaw obtained from vendors at different retail outlets were examined. A total of sixty ready-to-eat fruits were collected across different vending sites. The samples were processed aseptically using the serial dilution technique and then cultured on appropriate nutrient medium. The result obtained revealed that total bacterial count ranged 4.4x106cfu/g to 9.2x106cfu/g with garden eggs recording the lowest count and sliced watermelon samples harboring more bacteria than the rest of the samples. Similarly, the fungal load was in the range of 7.0 x 103cfu/g to 6.1 x 104cfu/g. Garden egg and sliced pineapple fruits had the lowest fungal load of 7.0 x 103cfu/g and 1.1 x 104cfu/g respectively. Organisms identified include Staphylococcus aureus, Aspergillus niger, E. coli, Enterobacter, Salmonella, Pseudomonas aeruginosa, Penicillium sp and Rhizopus stolonifer. The presence of coliform bacteria, and counts of ≥ 106 in most of the samples is a reflection of the sanitary quality of the processing of the produce and calls for concern. The findings from this study showed that the fruits contained microorganisms that are potentially pathogenic. Under favourable conditions, they may multiply and thus render the fruits unsafe for consumption as they could become means of food poisoning. Adequate training of food vendors to maintain high standard of personal and environmental hygiene, proper washing of fruits before consumption, regular washing of hands

TABLE OF CONTENTS

Title page                                                                                                                    i

Declaration                                                                                                                  ii

Certification                                                                                                                iii

Dedication                                                                                                                  iv

Acknowledgements                                                                                                    v

Table of contents                                                                                                        vi

List of tables                                                                                                               viii

Abstract                                                                                                                      ix

CHAPTER ONE: INTRODUCTION                                                                               

1.1       Aims and Objectives                                                                                       7

CHAPTER TWO: LITERATURE REVIEW

2.1       Overview of Street-Vended Foods                                                                10

2.2       Microbial Quality of Street Foods                                                                  12

2.3       Food-Borne Pathogens                                                                                   15

2.3.1    Bacillus cereus                                                                                                16

2.3.2    Salmonella species                                                                                          17

2.3.3    Enteropathogenic – Escherichia coli                                                              18

2.3.4    Staphylococcus aureus                                                                                    19

2.4       Food Handling and Practices                                                                         20

2.5       Importance of Cleaning and Sanitation of Fruits                                           21

CHAPTER THREE: MATERIAL AND METHODS

3.1       Sample Collection                                                                                           22

3.2       Media Preparation                                                                                           22

3.3       Preparation of Sample Homogenate                                                               22

3.4       Isolation and Enumeration of Microbial Isolates                                            23

3.5       Bacterial Identification                                                                                   23

3.5.1    Gram Staining                                                                                                 23

3.5.2    Biochemical Tests                                                                                           24

3.5.3    Catalase Test                                                                                                   24

3.5.4    Methyl Red Test                                                                                             24

3.5.5    Voges- Proskauer Test                                                                                    24

3.5.6    Indole Test                                                                                                      25

3.5.7    Citrate Utilization Test                                                                                   25

3.5.8    Hydrogen Sulphide (H₂S) Production Test                                                    25

3.6       Fungal Identification                                                                                      25

CHAPTER FOUR: RESULTS

4.1       Result                                                                                                              26

CHAPTER FIVE: DISCUSSION AND CONCLUSION

5.1       Discussion                                                                                                       32

5.2       Conclusion                                                                                                      35

References                                                                                                      37

LIST OF TABLES

Table              Title                                                                                                    Page

1          Mean bacterial and fungal load in cfu/g of the samples                                 27

2          Colonial Morphology and Biochemical Characteristics of the Isolates          28

3          Growth of Microorganisms from the Different Fruits                                    29

4          Distribution of Isolate in the Various Fruits                                                   30

5          Description of the Isolated Fungi                                                                   31

CHAPTER ONE

INTRODUCTION

Food either raw or cooked, hot or chilled that are ready for immediate consumption at the point of sale without further treatment are generally described as “ready-to-eat (Tsang, 2002).

Vended fruits are fruits that have been cut or sliced open and carried around by street vendors or hawkers at local markets or streets and such fruits are eaten immediately that is they are eaten without necessarily having to cut, peel or rinse them before consumption because they have already been prepared or packaged by the vendors. These vended fruits such as watermelon, pineapple, carrots, cucumber, tiger nuts are sold by unlicensed vendors or local hawkers who have little or no knowledge on food hygiene (Muinde and Kuria, 2005). They are usually packaged in small polyethene bags for sale. Well balanced diets, rich in fruits and vegetables are especially valuable for their ability to prevent vitamin C and vitamin A deficiencies as well as reducing the risk of several diseases such as atherosclerosis and cancer (Kalia and Gupta, 2006). Over the last few years, there has been a significant increase in the consumption of vended fruits in Nigeria. This is because they are easily accessible, conveniently, and most importantly, they are cheaper than the whole fruits. Other reasons include modern lifestyle, industrialisation, economic downturn, materialism and lack of time to prepare proper meal (Nielsen, 2006).

Fruits and vegetables are widely exposed to microbial contamination through contact with soil, dust and water and by handling at harvest or during postharvest processing. They therefore harbour a diverse range of microorganisms including plant and human pathogens (Nguyen and Carlin, 1994; Carmo et al., 2004). 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 via 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 (Amoah et al., 2009).

Thus despite their nutritional and health benefits, outbreaks of human infections associated with the consumption of fresh or minimally processed fruits and vegetables have increased in recent years (Beuchat, 2002). Enteric pathogens such as Escherichia coli and Salmonella are among the greatest concerns during food-related outbreaks (Buck et al., 2003). Bacteriologically safe fruits and vegetables are essential to maximize the health benefits promised by adequate consumption of these produce.

In developing countries, street  vended fruits plays a major role in the nutritional requirements of many people especially those whose schedule take them away from home during the day and sometimes in the night. Even though street vended fruits are relatively cheap and easily accessible, it has its associated health problems (Omemu and Aderoju, 2008). Since street vended fruits are ready-to-eat and does not usually go through further processing it can be a good vehicle for food-borne microbial organism transmission into the body, if it is not handled properly.

Bacteria such as Salmonella species, Staphylococci aureus and Escherichia coli, which can be conveyed by these fruits, cause food poisoning and other food-borne diseases such as typhoid fever and cholera (Foskett et al., 2003), dysentery, diarrhea and food poisoning (Macleod and Douglas, 1999). Vended fruits should not only be nutritionally balanced, but should be microbiologically safe as well. In recent times there have been reported cases of food-borne diseases such as typhoid fever, diarrhea and other intestinal related diseases which may be attributed to consumption of contaminated water used in washing and processing the fruits.

Safe food is a basic human right despite the fact many foods are frequently contaminated with naturally occurring pathogenic microorganisms which cannot be detected organoleptically (seen, smelled or tested) but can cause diseases including death especially if the way they are conserved during exposition for sale provides condition for those microorganisms to grow and reach considerable levels of contamination (WHO, 2000).

Street vended fruits are appreciated for their unique flavors and convenience. They also assure food security for low income urban population and livelihood for a significant proportion of the population in many developing countries (Amoah et al., 2009). However, the unhygienic conditions in which these foods are prepared, stored and served raise a question regarding their microbiological quality. Contamination of fruits by enteric pathogens can occur from the farm if human sewage is used to fertilize the soils or if sewage water is used to irrigate the crops. Such risks are further increased if the food is mishandled during processing and preparations where pathogens could multiply exponentially under favorable conditions (Amoah et al., 2009).

In Nigeria, there has been an increase in the consumption of ready-to-eat fruits over the last few years because they are relatively cheap, easily accessible and convenient. Also, they are easily available, affordable, provides divers/variable food source, employment.

Infectious food-borne diseases are of major public health importance worldwide and may not be eliminated in the foreseeable future (Nweze, 2010). Microorganisms are abundant and ubiquitous in nature and their role as causative agents of food borne illnesses was recognized way back in the 19th century. It was discovered by the end of the 19th century that microorganisms were responsible for a variety of food borne diseases (Nweze, 2010), Microbial contamination of foods present challenges that are different from those posed by toxins and physical hazards to the scientific, public health, and food authority communities in all countries.

Food borne illness is defined as diseases, usually either infectious or toxic in nature, caused by agents that enter the body though the ingestion of food (WHO, 2007). Food borne diseases are known to contribute to both human morbidity and mortality as well as to health care costs (Campbell et al., 1998). Foodborne diseases (FBDs) comprise a large group of illnesses that are caused by the ingestion of contaminated food (WHO, 2013). The infectious agents range from a multitude of microorganisms to some chemical hazards.

It has been shown that Street-vended foods have been implicated in outbreaks of foodborne illnesses all around the world (Bryan et al., 1992). Most food-related illnesses have historically been attributed to one of five major groups of pathogenic bacteria (Mboto et al., 2012). These five groups are Salmonella, Shigella, Clostridium botulinum, Clostridium perfringens, Bacillus cereus, and Staphylococcus aureus. These have been joined by the emerging pathogens such as Yersinia enterocolitica, Escherichia coli, Listeria monocytogens, and Campylobacter jejuni (Mboto et al., 2012).

Foodborne diseases of microbiological origin can be caused by a variety of agents, which gain entry by the gastrointestinal tract. However the symptoms are often mild and self-limiting. Symptoms of foodborne disease, which are not necessarily confined to diarrhoea and vomiting, are caused by viable organisms and/or by the toxins that they produce. The risk of disease from these agents varies depending on the pathogen, the dose, the host and the properties of the food matrix. Host risk factors include age, immune status, underlying debilitating disease or stress factors, and the physiological state of the stomach and upper small intestine at the time of exposure to the agent. For these reasons a minimum infectious dose cannot be defined, although the risk of disease at low exposure for some agents is small (Nweze, 2010). The presence of foodborne agents that may cause illness in ready-to-eat foods is a significant risk to consumer health and their absence is of paramount importance.

With the exception of the aerobic and anaerobic bacteria spores, detection of foodborne pathogenic agents at any level is of concern and should be investigated with an urgency of response proportionate to the level of contamination and risk to consumers. Although low numbers of pathogens, such as coagulase-positive staphylococci, C. perfringens, B. cereus, and L. monocytogenes, in ready-to-eat products probably represent a very low risk to immunocompetent people, they are more significant for the immunocompromised and vulnerable groups. Low levels may be due to natural contamination of raw materials used in those foods, but usually their presence suggests faults in the production or subsequent handling of food which could lead to an unacceptable increase in risk. There may also be a need for action when detecting low numbers of these organisms in ready-to-eat foods because there is variation in host susceptibility and inter strain differences in the pathogenicity of these bacteria.

The recurrent episodes of food borne illnesses with symptoms of gastro intestinal distress like diarrhea, vomiting, abdominal cramp and nausea has remained a major cause of mortality and morbidity in Nigeria.

1.1       Aims and Objectives

1.         To determine the total heterotrophic bacterial and fungal load of different fruit samples.

2.         To isolate and identify bacterial species associated with food contamination.

3.         To establish the public health implication of consumption of such fruits.