Foodborne Diseases

Christine ER Dodd, Tim Grant Aldsworth, Richard A Stein, Christine ER Dodd, Tim Grant Aldsworth, Richard A Stein

• Publisher: Academic Press
• Year: 2017
• ISBN:
  9780123850089
• Edition: 3
• Topic: Tecnología e ingeniería
• Subtopic: Ciencia de los alimentos

Foodborne Diseases, Third Edition, covers the ever-changing complex issues that have emerged in the food industry over the past decade. This exceptional volume continues to offer broad coverage that provides a foundation for a practical understanding of diseases and to help researchers and scientists manage foodborne illnesses and prevent and control outbreaks. It explains recent scientific and industry developments to improve awareness, education, and communication surrounding foodborne disease and food safety.

Foodborne Diseases, Third Edition, is a comprehensive update with strong new topics of concern from the past decade. Topics include bacterial, fungal, parasitic, and viral foodborne diseases (including disease mechanism and genetics where appropriate), chemical toxicants (including natural intoxicants and bio-toxins), risk-based control measures, and virulence factors of microbial pathogens that cause disease, as well as epigenetics and foodborne pathogens. Other new topics include nanotechnology, bioterrorism and the use of foodborne pathogens, antimicrobial resistance, antibiotic resistance, and more.

• Presents principles in disease processes in foodborne illness
• Includes hot-topic discussions such as the impact of nanotechnology on food safety
• Provides in-depth description of our current understanding of the infectious and toxic pathogens associated with food
• Presents cutting-edge research on epigenetics, antimicrobial resistance, and intervention technologies

Part 1

Principles

Outline

Chapter 1. Disease Processes in Foodborne Illness

Chapter 2. Epidemiology, Cost, and Risk Analysis of Foodborne Disease

Chapter 3. Routes of Transmission in the Food Chain

Chapter 4. Spread of Antibiotic Resistance in Food Animal Production Systems

Chapter 1

Disease Processes in Foodborne Illness

S.L. Taylor University of Nebraska, Lincoln, NE, United States

Abstract

Although food seldom transmits illness, there are several known ways in which foodborne illness can occur. Everyone is susceptible to infections and intoxications, although some portions of the population are at greater risk than others. Infections result from eating food containing a viable organism that multiplies in the body, sometimes causing disease. Intoxications result from eating food that contains a substance that poisons the body. In addition to these more frequent types of foodborne illness, there are others that affect only a select portion of the population. Allergies occur when food contains a substance to which the consumer is hypersensitive (generally an adverse immune mechanism), whereas metabolic disorders (some of which are called intolerances) involve the individual’s inability to process food components that are successfully digested by others. Idiosyncratic illnesses are events that may or may not be caused by components of food and that affect rare individuals in ways that are not yet understood.

Keywords

Adverse reactions to foods; Digestive tract; Disease processes; Food allergies; Infection; Intoxication; Intolerance; Foodborne illness; Metabolic food disorders

1.1. Classification of Disease Processes in Foodborne Illness

Foodborne diseases can be classified into five categories: infections, intoxications, metabolic food disorders, allergies, and idiosyncratic illnesses. Infections and intoxications can affect everyone. Metabolic food disorders, allergies, and idiosyncratic illnesses are sometimes referred to collectively as individualistic adverse reactions to foods because they affect only certain individuals in the population.

1.2. Structure and Function of the Digestive Tract

1.2.1. Anatomy and Digestive Functions

The digestive or gastrointestinal (GI) tract, especially the small intestine, is a primary site of action for foodborne infectious agents because they are ingested with food. All foodborne diseases start here. Let us, therefore, begin with a brief review of the anatomy and physiology of the GI tract.

The GI tract or alimentary canal is a hollow tube beginning at the mouth and terminating at the anus (Fig. 1.1). The folded tube is several times longer than the height of the individual it serves. Food moves through the open area of the tube, which is called the lumen. The lumen is technically outside the body and is separated from the interior of the body by a lining known as the mucosa. The GI tract has many additional layers, some of which comprise smooth muscles that move intestinal contents through the lumen by rhythmic contraction (peristalsis). Some regions of the GI tract are separated by sphincters, circular muscles that control the passage of food.

The primary physiological functions of the GI tract are digestion and absorption. Digestion is the process of breaking down food into components that can be absorbed or taken into the body.

Food enters via the mouth, where it is chewed by the teeth and mixed with saliva, which moistens the food, lubricates the upper portions of the GI tract, and provides amylase, a digestive enzyme that degrades starch into absorbable sugar subunits. The esophagus is the conduit from the mouth to the stomach. Food passes through the esophagus by rhythmic contractions and gravity. A sphincter at the bottom of the esophagus allows food to enter the stomach but also prevents digestive juices and food from being moved back into the esophagus.

Figure 1.1 The organs of the gastrointestinal tract.

The stomach functions partly as a reservoir until the lower portions of the GI tract are ready to receive and process the food; the stomach of an adult can hold 1–2 L of food and fluid. The stomach also produces HCl and pepsin, a proteolytic enzyme, and mixes these with the food. Digestion begins in earnest in the stomach, but very little absorption occurs, with the exception of small amounts of water, alcohol, and certain drugs. The contents empty through the pylorus (another sphincter) into the small intestine over a period of hours.

The small intestine, the major site for digestion of food and absorption of its nutrients, is divided into three sections: duodenum, jejunum, and ileum. Digestion occurs primarily in the duodenum or first portion of the small intestine. The duodenum receives secretions from the pancreas with enzymes that digest fats, carbohydrates, and proteins. The duodenum also receives bile, which is secreted from the liver and stored in the gallbladder. Bile emulsifies fats for easier digestion and absorption.

Absorption of the nutrients occurs throughout the length of the small intestine. A cross section of the jejunum is depicted in Fig. 1.2. The small intestine has a large surface area for absorption due to numerous fingerlike projections (villi) that extend into the intestinal lumen. To envision the millions of villi lining the surface of the small intestine, imagine a tube lined with terry cloth. Fig. 1.3 shows an enlarged version of one villus with an adjoining crypt. Projecting from the villi are even smaller strands called microvilli, which contain many of the enzymes and receptors involved in nutrient absorption. This convoluted surface multiplies the absorptive area approximately 600-fold in comparison to a flat, smooth surface. If flattened, the absorptive surface of the small intestine would measure approximately 200 m², the size of a tennis court.

Figure 1.2 Diagram of the layers of the small intestine. Reprinted with permission from P.L. Smith, 1986. Gastrointestinal physiology. In: Rozman, K., Hanninen, O. (Eds), Gastrointestinal Toxicology. Elsevier, New York, pp. 1–28.

Absorption takes place via the columnar epithelial cells (Fig. 1.3) near the tip of the villus—a term that describes their general shape and location as part of the intestine’s epithelial layer. The mature absorptive cells of the villus differentiate from precursor cells in the crypts. The villous tip cells have a short half-life; they are constantly being sloughed into the intestinal lumen and replaced by cells migrating from the crypts. The epithelial layer covering the villus also contains various specialized cells. Among the most common of these is the goblet cell (Fig. 1.3), which secretes mucin that adheres to the outer surface of the villus. Endocrine cells are also present in the epithelial layer and secrete GI hormones. The lamina propria is the area just below the surface epithelial cells. The lamina propria contains phagocytic cells, such as macrophages, lymphocytes, and plasma cells, which defend against invasion by foreign microorganisms or proteins.

Each villus contains a network of capillaries, which carry water-soluble nutrients to the blood, and a lacteal (a terminal portion of the lymphatic system), which carries fat-soluble products of digestion. The lymph eventually empties into the bloodstream. The small intestine normally absorbs 90% or more of the energy value of the consumed food. Micronutrients such as minerals and vitamins are absorbed somewhat less efficiently.

The large intestine (or colon or bowel) is the last major section. It is a collecting chamber for solid waste; contents usually spend 24 h or longer in this section. Bacteria flourish in the colon due, in part, to the slow movement of the contents. The bacteria feed on remaining food macronutrients. Some of the products of bacterial action are absorbed from the colon; up to 10% of the available energy from foods is absorbed from the large intestine. The bacteria may synthesize important quantities of certain micronutrients, including vitamin K and some of the B vitamins. S...