Food Contamination and Food-borne Diseases

By :

Dr. Nazik Eltayeb Musa Mustafa

Nov. 2012

الرحيم الرحمن الله بسم

Definition of food contamination• The presence in food of harmful, unpalatable,

or otherwise objectionable foreign substances,

e.g.

• Chemicals,

• Biological (microorganisms )

Or

• physical materials ,

before, during, or after processing or storage.

•

The concept of the Food chain

• Although almost all foods have an agricultural origin but it is clear that, in general, many other steps precede food consumption.

• These steps including procurement of raw materials, primary production processes, manufacturing practices and retailing.

• The food chain developed to maintain an appropriate food supply for consumers but it is also the main structure from which food safety can be assessed and managed.

The Food chain

Contamination of food during primary production till consumption

Biological contaminants

• Viruses, Bacteria, Moulds and Parasites

Chemical contaminants

Pesticide, Veterinary drugs (antibiotics hormones, heavy metals, toxic chemicals ( PCBs, Dioxins , Melamine… etc) and radioactive materials.

Food-borne diseases and biological causative agents

PATHOGENIC BACTERIA• Salmonella spp. • Clostridium botulinum • Staphylococcus aureus • Campylobacter jejuni • Yersinia enterocolitica and Yersinia

pseudotuberculosis • Listeria monocytogenes • Vibrio cholerae O1 • Vibrio cholerae non-O1 • Vibrio parahaemolyticus and other

vibrios • Vibrio vulnificus • Clostridium perfringens • Bacillus cereus • Aeromonas hydrophila and other

spp. • Plesiomonas shigelloides • Shigella spp. • Miscellaneous enterics • Streptococcus

ENTEROVIRULENT ESCHERICHIA COLI GROUP (EEC Group)

• Escherichia coli - enterotoxigenic (ETEC)

• Escherichia coli - enteropathogenic (EPEC)

• Escherichia coli O157:H7 enterohemorrhagic (EHEC)

• Escherichia coli - enteroinvasive (EIEC)

PATHOGENIC BACTERIA• Salmonella spp. • Clostridium botulinum • Staphylococcus aureus • Campylobacter jejuni • Yersinia enterocolitica and Yersinia

pseudotuberculosis • Listeria monocytogenes • Vibrio cholerae O1 • Vibrio cholerae non-O1 • Vibrio parahaemolyticus and other

vibrios • Vibrio vulnificus • Clostridium perfringens • Bacillus cereus • Aeromonas hydrophila and other

spp. • Plesiomonas shigelloides • Shigella spp. • Miscellaneous enterics • Streptococcus

ENTEROVIRULENT ESCHERICHIA COLI GROUP (EEC Group)

• Escherichia coli - enterotoxigenic (ETEC)

• Escherichia coli - enteropathogenic (EPEC)

• Escherichia coli O157:H7 enterohemorrhagic (EHEC)

• Escherichia coli - enteroinvasive (EIEC)

PARASITIC PROTOZOA and WORMS

• Giardia lamblia • Entamoeba histolytica • Cryptosporidium parvum • Cyclospora cayetanensis • Anisakis sp. and related worms • Diphyllobothrium spp. • Nanophyetus spp. • Eustrongylides sp. • Acanthamoeba and other free-

living amoebae • Ascaris lumbricoides and

Trichuris trichiura

VIRUSES• Hepatitis A virus • Hepatitis E virus • Rotavirus • Norwalk virus group • Other viral agents

NATURAL TOXINS• Ciguatera poisoning • Shellfish toxins (PSP,

DSP, NSP, ASP) • Scombroid poisoning • Tetrodotoxin (Pufferfish) • Mushroom toxins • Aflatoxins • Pyrrolizidine alkaloids • Phytohaemagglutinin

(Red kidney bean poisoning)

• Grayanotoxin (Honey intoxication)

OTHER PATHOGENIC AGENTS

• Prions

Staphylococcus aureus

Staphylococcus aureus is a spherical bacterium (coccus) . On microscopic examination appears in pairs, short chains, or bunched, grape-like clusters.

These organisms are Gram-positive. Some strains are capable of producing a highly heat-stable protein toxin that causes illness in humans.

staphylococcal food poisoning is usually rapid and in many cases acute, depending on individual susceptibility to the toxin, the amount of contaminated food eaten, the amount of toxin in the food ingested, and the general health of the victim.

The most common symptoms are nausea, vomiting, retching, abdominal cramping, and prostration. Some individuals may not always demonstrate all the symptoms associated with the illness. In more severe cases, headache, muscle cramping, and transient changes in blood pressure and pulse rate may occur. Recovery generally takes two days, However, it us not unusual for complete recovery to take three days and sometimes longer in severe cases.

Food Incriminated Foods that are frequently incriminated in staphylococcal food

poisoning include: meat and meat products; poultry and egg products; salads such as egg, tuna, chicken, potato, and macaroni; bakery products such as cream-filled pastries, cream pies, and chocolate eclairs; sandwich fillings; milk and dairy products. Foods that require considerable handling during preparation and

that are kept at slightly elevated temperatures after preparation are frequently involved in staphylococcal food poisoning

sources

Staphylococci exist in air, dust, sewage, water, milk, and food or on food equipment, environmental surfaces, humans, and animals. Humans and animals are the primary reservoirs.

Bacillus cereus

Bacillus cereus is a Gram-positive, facultatively aerobic sporeformer whose cells are large rods and whose spores do not swell the sporangium.

Bacillus cereus food poisoning

two recognized types of illness are caused by two distinct metabolites. The diarrheal type of illness is caused by a large molecular weight protein, while the vomiting (emetic) type of illness is believed to be caused by a low molecular weight, heat-stable peptide.

The diarrheal type

The onset of watery diarrhea, abdominal cramps, and pain occurs 6-15 hours after consumption of contaminated food. Nausea may accompany diarrhea, but vomiting (emesis) rarely occurs. Symptoms persist for 24 hours in most instances.

The emetic type

is characterized by nausea and vomiting within 0.5 to 6 h after consumption of contaminated foods. Occasionally, abdominal cramps and/or diarrhea may also occur. Duration of symptoms is generally less than 24 h.

Associated Foods

wide variety of foods including meats, milk, vegetables, and fish have been associated with the diarrheal type food poisoning.

The vomiting-type outbreaks have generally been associated with rice products; however, other starchy foods such as potato, pasta and cheese products have also been implicated. Food mixtures such as sauces, puddings, soups, casseroles, pastries, and salads have frequently been incriminated in food poisoning outbreaks

Clostridium botulinum

Clostridium botulinum is an anaerobic, Gram-positive, spore-forming rod that produces a potent neurotoxin. The spores are heat-resistant..

Rights preserved to Nazik E. M. Mustafa 2004

Rights preserved to Nazik E. M. Mustafa 2004

Seven types (A, B, C, D, E, F and G) of botulism are recognized, based on the antigenic specificity of the toxin produced by each strain. Types A, B, E and F cause human botulism. Types C and D cause most cases of botulism in animals

Animals most commonly affected are wild fowl and poultry, cattle, horses and some species of fish. Although type G has been isolated from soil in Argentina, no outbreaks involving it have been recognized.

Name of the Disease

Four types of botulism are recognized: foodborne, infant, wound, and a form of botulism whose classification is as yet undetermined. Certain foods have been reported as sources of spores in cases of infant botulism and the undetermined category; wound botulism is not related to foods.

Foodborne botulism is the name of the disease (actually a food-borne intoxication) caused by the consumption of foods containing the neurotoxin produced by C. botulinum.

Nature of the Disease

Infective dose : a very small amount (a few nanograms) of toxin can cause illness

Associated Foods

The types of foods involved in botulism vary according to food preservation and eating habits in different regions. Any food that is conducive to outgrowth and toxin production, that when processed allows spore survival, and is not subsequently heated before consumption can be associated with botulism. Almost any type of food that is not very acidic (pH above 4.6) can support growth and toxin production by C. botulinum.

Food Analysis

Since botulism is foodborne and results from ingestion of thet toxin of C. botulinum, determination of the source of an outbreak is based on detection and identification of toxin in the food involved. The most widely accepted method is the injection of extracts of the food into passively immunized mice (mouse neutralization test). The test takes 48 hours. This analysis is followed by culturing all suspect food in an enrichment medium for the detection and isolation of the causative organism. This test takes 7 days.

Salmonellosis

• Salmonella is a rod-shaped Gram negative , motile bacterium - few are nonmotile. There is a widespread occurrence in animals, especially in poultry and swine

sources

• Raw meats, raw poultry, and raw seafoods are main sources

Nature of Disease

Acute symptoms - Nausea, vomiting, abdominal cramps, minimal diarrhoea, fever, and headache. Chronic consequences may occur

ENTEROVIRULENT Escherichia coli GROUP (EEC )

• Escherichia coli - enterotoxigenic (ETEC) • Escherichia coli - enteropathogenic (EPEC) • Escherichia coli O157:H7

enterohemorrhagic (EHEC) • Escherichia coli - enteroinvasive (EIEC)

Escherichia coli O157:H7Enterohemorrhagic E. Coli (EHEC)

• E. coli is a normal inhabitant of the intestines of all animals and humans.

• Most strains of E. coli are harmless.

• E. coli serotype O157:H7 is a rare variety of E. coli that produces potent toxins that could cause severe damage to the lining of the intestine (Hemorrhagic colitis).

E. coli Hemorrhagic colitis is characterized by:

-Severe cramping- Diarrhoea which is initially watery but

becomes grossly bloody. -Vomiting (occurs occasionally). - Low-grade fever or absent of fever. The illness is usually self-limited and lasts for an

average of 8 days. Some individuals exhibit watery diarrhea only.

Sources

• The reservoir of this pathogen appears to be mainly cattle and other ruminants such as camels.

• The disease is usually a associated with raw or undercooked ground meat products and raw milk ( e.g. Undercooked Hamburger).

• Some outbreaks are associated with the consumption of fruits and vegetables

• Faecal contamination of water and other foods, as well as cross-contamination during food preparation (with beef and other meat products, contaminated surfaces and kitchen utensils), will also lead to infection.

Microbiological Food Analysis

The organism can not ferment sorbitol . This feature is used to differentiate it from other E. coli strains

Hemorrhagic colitis agar is a selective and differential medium used in a direct plating method to isolate O157:H7 from foods.

Campylobacteriosis

• Is the diseases caused by the bacterium Campylobacter jejuni. It is also often known as campylobacter enteritis or campylobacter gastroenteritis.

Campylobacter jejuni

• Campylobacter jejuni is a Gram-negative slender, curved, and motile rod. It is a microaerophilic organism

sources

• C. jejuni frequently contaminates raw chicken.

• Raw milk is also a source of infections. The bacteria are often carried by healthy cattle and by flies on farms.

Shigellosis

• This disease occur when Shigella species invade the colonic epithelium through M cells and then spread laterally from cell-to-cell. This invasive ability is due to several virulence factors encoded by a high molecular weight virulence plasmid.

• Shigella species are transmitted by ingestion of contaminated food or water.

• In addition, S. dysenteriae secretes the Shiga toxin, which inhibits protein synthesis in eukaryotic cells via inactivation of ribosomal RNA, leading to cell death.

Listeriosis is the name of the general group of disorders caused by L. monocytogenes

Listeriosis

Listeria monocytogenes

This is a Gram-positive bacterium, motile by means of flagella.

Nature of Disease

Listeriosis is clinically defined when the organism is isolated from blood, cerebrospinal fluid, or an otherwise normally sterile site (e.g. placenta, fetus).

Some studies suggest that 1-10% of humans may be intestinal carriers of L. monocytogenes. It has been found in at least 37 mammalian species, both domestic and feral, as well as at least 17 species of birds and possibly some species of fish and shellfish.

L. monocytogenes is quite hardy and resists the deleterious effects of freezing, drying, and heat remarkably well for a bacterium that does not form spores. Most L. monocytogenes are pathogenic to some degree.

Sources

Can be isolated from soil, silage, and other environmental sources.

Diagnosis of Human Listeriosis

can only be positively diagnosed by culturing the organism from blood, cerebrospinal fluid, or stool (although the latter is difficult and of limited value).

Associated Foods

L. monocytogenes has been associated with:• raw milk, cheeses (soft-ripened varieties),• ice cream, • raw vegetables,• fermented raw-meat sausages, • raw and cooked poultry,• raw meats (all types), • and raw and smoked fish. • refrigerated foods( due to its ability to grow at

temperatures as low as 3°C which permits multiplication in cold food).

Food Analysis

The methods for analysis of food are complex and time consuming. Some methods requires 24 and 48 hours of enrichment, followed by a variety of other tests.

Recombinant DNA technology may even permit 2-3 day analysis

VirusesViruses are very simple organisms that cannot

replicate outside a susceptible host cell and do not therefore multiply in foods.

Food and water can, however, be the vehicle for transmission of a number of different viruses that infect humans via the gastrointestinal tract. This is invariably the result of contamination of food by faeces or vomitus from an infected individual, possibly via some intermediary vehicle such as water or equipment.

.

Poliomyelitis and hepatitis A are the most serious viral diseases that are known to be transmitted by this route;

Hepatitis E, which can be waterborne, is a significant cause of infectious hepatitis in Asia and Africa. There are also a number of food and waterborne viruses that cause diarrhoea, most notably the small round structured viruses or Norwalk-like agents and Rotavirus

VIRAL GASTROENTERITIS

Gastroenteritis means inflammation of the stomach and small and large intestines.

Viral gastroenteritis is an infection caused by a variety of viruses that results in vomiting or diarrhea.

Many different viruses can cause gastroenteritis, including :

• Rotaviruses

• adenoviruses

• caliciviruses

• astroviruses

• Norwalk virus and a group of Norwalk-like viruses.

symptoms of viral gastroenteritis

The main symptoms of viral gastroenteritis are watery diarrhea and vomiting.

The affected person may also have headache, fever and abdominal cramps.

In general, the symptoms begin one to two days following infection with a virus that causes gastroenteritis and may last for one to 10 days, depending on which virus causes the illness

sources

Food may be contaminated by -food preparers or handlers who have viral

gastroenteritis. -Shellfish may be contaminated by sewage.

Persons who eat raw or undercooked shellfish harvested from contaminated waters may get diarrhea. Drinking water can also be contaminated by sewage and be a source of the spread of these viruses

NORWALK VIRUS

It is estimated that Norwalk viruses are responsible for about one-third of the cases of viral gastroenteritis not involving the 6 to 24-month age group.

Approximately 181,000 cases occur annually, with no known associated deaths. Norwalk and Norwalk-like viruses have been associated with outbreaks on cruise ships and in communities, camps, schools, institutions and families.

sources

Raw oysters, cake frosting and salads, as well as drinking water, have been implicated as a common source of viral infection in several outbreaks.

ROTAVIRUS

Rotavirus is the leading cause of severe diarrhea among infants and children and accounts for about half of the cases requiring hospitalization. Over three million cases of rotavirus gastroenteritis occur annually in the United States, primarily in the winter.

All age groups are susceptible to rotavirus infection, but children six months to 2 years of age, premature infants, the elderly, and the immune-compromised are particularly prone to more severe symptoms. Outbreaks of rotavirus diarrhea are common among hospitalized infants, young children attending day care centers and elderly persons in nursing homes.

Other viruses

Astroviruses cause sporadic gastroenteritis in children under 4 years of age and account for about 4 percent of the cases hospitalized for diarrhea.

Caliciviruses infect children between 6 and 24 months of age and account for about 3 percent of hospital admissions for diarrhea. By 6 years of age, more than 90 percent of all children have developed immunity to the illness

The enteric adenovirus causes 5 to 20 percent of the gastroenteritis in young children, and is the second most common cause of gastroenteritis in this age group. By 4 years of age, 85 percent of all children have developed immunity to the disease

Hepatitis A

the most common type of hepatitis, is usually a mild illness characterized by sudden onset of fever, nausea, vomiting, fatigue and abdominal pain, followed in several days by jaundice. Other symptoms include pain in the liver area, dark urine and light-colored stools.

.

• The incubation period for hepatitis A varies from 10 to 50 days, which means that infected persons can spread the disease before they realize they have it. Young children often do not show clinical signs of the disease but can still be contagious. The disease is usually mild and recovery complete in one to two weeks. Occasionally, the symptoms are severe and convalescence can take several months

Hepatitis E

can also be transmitted by the fecal-oral route and can be foodborne. Symptoms are clinically indistinguishable from hepatitis A. 

Avian influenza

• Before the outbreaks in Hong Kong (1997) and in the Netherlands (2003), human infection with avian influenza viruses were rarely reported and usually resulted in mild disease.

• Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 has caused the largest number of cases of severe disease and death in humans

• Unlike normal seasonal influenza, where infection causes self-limited respiratory symptoms in most people, the disease caused by H5N1 follows an unusually aggressive clinical course, with rapid deterioration and high fatality.

• the virus – if given enough opportunities – could change into a form that is highly infectious for humans and spreads easily from person to person.

The H5N1 avian influenza and food

• The H5N1 avian influenza virus spreads to virtually all parts of an infected bird, including blood, meat and bones.

• Avian influenza viruses survive in contaminated raw poultry meat and therefore can be spread through the marketing and distribution of contaminated food products, such as fresh or frozen meat.

• The viability of the avian influenza virus is maintained at low temperatures.

• The H5N1 avian influenza virus can survive in faeces for at least 35 days at 4 °C and at least six days at 37 °C.

• The virus has also been shown to survive on surfaces for several weeks at ambient temperatures.

• In areas affected by Avian influenza A/H5N1 virus, handling of frozen or thawed raw infected poultry meat prior to cooking may be hazardous, if good hygienic practices are not observed.

• In areas experiencing outbreaks like Sudan, poultry and poultry products can also be safely consumed provided these items are properly cooked and properly handled during food preparation. The virus is inactivated at temperatures reached during conventional cooking (70 °C in all parts of the food (

BSE (bovine spongiform encephalopathy)

• BSE (bovine spongiform encephalopathy) is a fatal disease that causes progressive neurological degeneration in cattle.

• Creutzfeldt-Jakob disease (CJD) is a rare disease that occurs in humans similar to BSE.

• In 1996, following outbreaks of BSE among British cattle, scientists found a possible link between BSE and a new variant of CJD (vCJD).

• While it is not certain how BSE may be spread to humans, evidence indicates that humans may acquire vCJD after consuming BSE-contaminated cattle products.

The causative agent

• The causative agent is a prion (unusual proteins)

Histopathology

• Spongiform changes

(holes)