Microbial Food Spoilage Disorders (Diseases) And It’s Control

Project and Seminar Material for Biochemistry

Microbial Food Spoilage Disorders (Diseases) And It’s Control


Foods and microorganisms have long and interesting associations which developed long before the beginning of recorded history. Foods are not only nutritious to consumers, but are also excellent sources of nutrients for microbial growth. Depending on the microorganisms present, foods may spoil or be preserved by fermentation. Foods can act as a reservoir for disease transmission, and thus detection and control of pathogens and spoilage organisms are important areas of food microbiology.

During the entire sequence of food handling from the producer to the final consumer, microorganisms can affect food quality and develop potential health effects for humans. Food spoilage is a metabolic process that causes foods to be undesirable or unacceptable for human consumption due to changes in sensory characteristics (tactile, visual, olfactory or flavour). Chemical reactions that cause offensive sensory changes in foods are mediated by a variety of microbes that use food as a carbon and energy source. These organisms include bacteria, fungi, protozoa and viruses. Many physical and chemical methods are employed to control the growth of certain microbes on foods thereby preventing their spoilage.

Table Of Contents

Preliminary Page(s)

  • Title page i
  • Certification page ii
  • Dedication iii
  • Acknowledgement iv
  • Abstract v
  • Table of content

Chapter One:


  • 1.1 Background of Study
  • 1.2 Statement of Problem
  • 1.3 Research Objectives
  • 1.4 Research Questions
  • 1.5 Significance of Study

Chapter Two:

Literature Review

  • 2.1 Introduction
  • 2.2 Food items that are commonly hawked (cooked or uncooked)
  • 2.3 Microorganisms associated with food items
  • 2.4 Prevalence of microorganism in ready-to-eat foods
  • 2.5 Isolation of microorganism from ready-to-eat foods
  • 2.6 Antibiotics susceptibility of microbial contaminants isolated from ready-to-eat foods
  • 2.7 Microbial polymerase chain reaction (PCR)

Chapter Three:

Materials And Methods

  • 3.1 Materials
  • 3.2 Sample collection
  • 3.3 Sample preparation
  • 3.4 Sub-culturing and storage of the microbial isolates
  • 3.5 Identification and characterization of bacterial isolates
  • 3.6 Characterisation and identification of fungal isolates
  • 3.7 Susceptibility test for bacterial isolates
  • 3.8 Susceptibility test for fungi isolates
  • 3.9 Multiple antibiotic resistance index (MARI)
  • 3.10 Identification of resistant genes in aspergillus species

Chapter Four:

Results And Discussion

  • 4.1 Results
  • 4.2 Discussion

Chapter Five:

Conclusion And Recommendations

  • 5.1 Conclusion
  • 5.2 Recommendations
  • References
  • Appendix

Chapter One


1.1 Background of Study

Bacterial are group of microorganism all of which lack a distinct nuclear membrane (and hence are considered more primitive than animal and plant cells) and most of which have a cell wall of unique composition. Most bacterial are unicellular; the cells may be spherical (coccu) rod – shaped (bacillus), spiral (spirillum), comma – shaped (vibrio) or corkscrew-shaped (spierocheate). Generally, they range in size between 0.5 and 5um. (Elizabeth and Martin, 2003).
Food is any substance that people or animal eat or drink or that plants absorb to maintain life and growth. Food is any substance consumed for nutritional support for the body; it is usually of plant or animal origin (Ezeronye, 2007). Food consists of chemical compounds which heterophilic living thing consumes in order to carry out metabolic processed. They are also substances which when introduced to the digestive system under normal circumstances contribute to growth, repair and production of energy (Ezeronye, 2007). Foods are classified into six essential nutrients known as protein, carbohydrate, vitamin mineral, fat and oil, water.


One of a group of organic compounds of carbon, hydrogen, oxygen and nitrogen (sulphur and phosphorus may also be present). The protein molecule is a complex structure made up of one or more chains of amino acid, which are linked by peptide bonds. Proteins are essential constituents of the body; they form the structural material of muscles, tissues, organs, etc. and are equally important as regulators of function, as enzymes and hormones, proteins are synthesized in the body from their constituent amino acids, which are obtained from the digestion of protein in the diet (Elizabeth and Martin, 2003).


One of a large group of compounds, including the sugar and starch, that contain carbon, hydrogen and oxygen and have the generalformula CX (H20) Y- Carbohydrates are important as a source of energy: they are manufactured by plants and obtained by animals from the diet, being one of the three main constituent of food. All carbohydrates are eventually broken down in the body to the simple sugar glucose which canthen take part in energy producing metabolic processes. Excess carbohydrate, not immediately required by the body is stored in the liver and muscles in the form of glycogen. In plants carbohydrate are important structural materials (e.g. cellulose and storage products (commonly in the form of starch) (Elizabeth and Martin, 2003).


Any of a group of substances that are required in very smallamounts, for healthy growth and development: they cannot be synthesized by the body and are therefore essential constituents of the diet. Vitamins are divided into two groups, according to whether they are soluble in water or fat. The water soluble groups include the vitamin C; the fat soluble vitamins are vitamins A, D, E and K. Lack of sufficient quantities of any of the vitamins in the diet results in specific vitamin deficiency diseased (Elizabeth and Martin, 2003).


A substance that contains one or more fatty acids (in the form of triglyceride) and is the principal form in which energy is stored by the body (in adipose tissue). It also serves as an insulating material beneath the skin (in the subcutaneous tissue) and around certain organs (including thekidney). Fat is one of the three main constituents of food; it is necessary in the diet to provide an adequate supply of essential fatty acid and from the efficient absorption of fat –soluble vitamins from the intestine. Excessive deposition of fat in the body leads to obesity (Elizabeth and Martin, 2003).

1.2 Statement of Problem

Poor sanitary condition in most of the local markets and the environment being highly polluted and charged with spoilage and pathogenic flora is likely the source of contamination of food items sold by such sellers (Oweghe et al., 2001). It is known that poor hygienic conditions in a food environment may encourage the multiplication of pathogenic organisms in food (Egeonu, 2002). It has been observed that Bacillus cereus and Staphylococcus aureus grow to oxygenic levels in food at 300c (Egeonu, 2003). Therefore microbiological examination of foods and food contact surfaces may provideinformation concerning the quality of the raw food, and the sanitary conditions under which the food is processed (Michael et al; 2004). Microorganisms live throughout the kitchen and can easily move around by attaching themselves to people easily move around by attaching themselves to people, food and equipment. Bacteria may pass from equipment to food which has not been properly cleaned and sanitized before being used to prepare another food. This implies that the food to be consumed by humans should be pure and free from contamination especially by pathogenic and spoilage microorganisms. Failure to ensure the safety and wholesomeness of the food consumed by the public might lead to some illness. To reduce contamination by microorganisms to a minimum level, and obtain good keeping quality of the products, the raw materials should regularly be monitored and examined.

Food contacts surfaces are a major concern for food service facilities in controlling the spread of food-borne pathogens, surfaces such as bench tops, table, etc. may have bacterial on them from contact with people, raw foods, dirty equipment or other things such as cartons that have been storedon the floor. If the bench tops are not properly cleaned, any food on them will be contaminated by the bacterial (Kamil, 2005).

1.3 Research Objectives

The overall objective of this work is to access selected foods sold inNsukka town, Enugu for bacterial contamination. The specific objectives are however given as;

  1. To isolate and identify bacterial species associated with food contamination.
  2. To determine the microbial load of isolated bacteria.
  3. To establish the public health implication of consumption of such foods.

1.4 Research Questions

  1. What are the bacterial species associated with food contamination?
  2. What is the microbial load of isolated bacteria?
  3. What is the public health implication of consumption of such foods?

1.5 Significance of Study

Food is very important for the sustenance of the human health. However, the preparation of foods is often associated with inadvertent contamination by microorganisms. Food contamination by antimicrobial resistant organisms has become a serious problem in public health. The emergence of resistant organisms has been observed to be as a result of inappropriate use of antibiotics. Evidence has shown that the use of antibiotics in animal has resulted to resistance food borne pathogens that may be transmitted to humans as food contaminants.

This study was designed with a view to ascertain the diversity of bacterial and fungal contaminants in foods. The microbial contaminants are to be isolated, identified, and their susceptibilities to commonly available antibiotics determined. For resistant isolates, the possible resistance gene(s) involved will be identified. The findings will be discussed in relation to the potential public health implications of eating microbial contaminated foods and will be of immense benefit to the public as well as food related organisations.

Chapter Five

Conclusion And Recommendations

5.1 Conclusion

This study has demonstrated that ready-to-eat food in Nsukka are contaminated with microorganisms such as Enterobacter aerogenes, Staphylococcus aureus, Bacillus spp., Shigella dysenteriae, Aspergillus spp. and Candida spp. This study also showed the presence of multidrug resistant microorganisms in ready-to-eat foods in Nsukka. Consumption of these foods may be harmful to the health and the consumers of these foods may be placed at high health risk which may lead to failures of commonly used clinical antibiotics for the treatment of infections. The susceptibility test has revealed the drugs of choice to be used in the treatment of food borne illnesses. We can infer that the Aspergillus spp have the resistant gene, MDR3 in them and this may be responsible for their resistance to antifungal agents.

5.2 Recommendations

Based on the findings of this research work, the following recommendations were made;

  1. There is need to create awareness on food borne illnesses or diseases, in order to improve the hygienic and sanitary practices among food sellers and hawkers. NAFDAC should enforce strict compliance to Hazard Analysis Critical Control Points in food production
  2. In addition, regulatory bodies should also ensure that foodstuffs do not contain microorganisms or their toxins in quantities that can affect human health and monitor the foods vended and the quality of the foods sold to the public to avoid outbreak of food borne disease.
  3. Proper sanitation and cleanliness measures should be adopted by the food sellers, as well as ensure that their foods sold are done so in clean and healthy environment.
  4. Proper regulatory measures should be adopted for the monitoring of the health and public implications of food sellers for community and individual health.

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