Foodborne Infection

Question 1

PHYSICAL HAZARDS

Answer 1

Physical hazards are foreign materials and objects that can enter the food we eat. This is also known as extraneous matter.

Question 2

Phhysical hazards can cause;

Answer 2

1) Cuts to the mouth and gums.

2) Damage to teeth.

3) Injury to the throat, oesophagus (food pipe), stomach, and intestines.

4) Some people may require surgery to remove the
offending item. Choking, which can be fatal.

Question 3

CHEMICAL HAZARDS

Answer 3

1) Chemicals are substances that can be naturally occurring or they can be human-made.

2) Sometimes intentionally added to our food for taste and
preservation purposes, e.g. sodium nitrates and sulphites.

3) Some chemicals can also be unintentionally added, which can contaminate the food we eat.

4) Sometimes, allergens are also classed as chemical hazards.

Question 4

Toxins that are produced by animals, plants, and microorganisms.
For example:

Answer 4

1) Mycotoxins – Produced by fungi.

2) Aflatoxins – Found in peanuts, tree nuts, and corn.

3) Ochratoxins – Found in vine fruits such as currants, raisins, and sultanas.

4) Marine toxins – Found in fish and shellfish.

5) Natural toxins – Produced by plants, e.g. glycoalkaloids in potatoes.

6) Bacterial toxins – Produced by bacteria such as E.coli O157.

Question 5

MICROBIOLOGICAL HAZARD

Answer 5

Biological or microbiological hazards occur when
microorganisms contaminate our food. Therefore,
they can easily enter and contaminate our food throughout the entire supply chain.

Question 6

Microorganisms include in MH;

Answer 6

1) Bacteria, e.g. salmonella, listeria, and campylobacter.
2) Fungi, e.g. yeasts and molds.
3) Viruses, e.g. norovirus and hepatitis A virus.
4) Parasites, e.g. worms and protozoa (Toxoplasma gondii and Giardia lamblia).

Question 7

Food borne diseases

Answer 7

 Food borne diseases (FBD) are acute illnesses associated with the recent consumption of food
 The food involved is usually contaminated with a disease
pathogen or toxicant.
 Such food contains enough pathogens or toxicant necessary to make a person sick.

Question 8

Classification of food borne diseases

Answer 8

1. Food borne infections and
2. Food borne intoxications

Question 9

Food borne infections

Answer 9

Food borne infections are caused by the entrance of pathogenic microorganisms contaminating food into the body and the reaction of the body tissues to their presence.
These can either be fungal, bacterial, viral, or parasitic
Food borne infections tend to have long incubation periods and are usually characterized by fever

Question 10

Bacterial food borne infections

Answer 10

Cholera, salmonellosis, typhoid fever, shigellosis, Yersiniosis, Escherichia coli infection Campylobacteriosis, Vibrio parahemolyticus, and Listeriosis

Question 11

Mycotic food borne infections

Answer 11

Candida spp., Sporothrix spp., Wangiella spp. etc),

Question 12

Viral food borne infections

Answer 12

Hepatitis A , Norwak virus and poliomyelitis virus

Question 13

Salmonellosis

Answer 13

 Many salmonella species have a wide host range. These are the organisms, which commonly cause food poisoning.

 However, some are restricted to a single host species
e.g. Salmonella abortus ovis causing abortion in ewes, and Salmonella gallinarum the cause of fowltyphoid.

 Conversely, some salmonella serotypes are associated with human disease and are not known to affect animals e.g. S. typhi and Salmonella paratyphi.

 Salmonellae are ubiquitous in the gut of human and
animals and act as sources of food contamination.

 A heavy dose up to 10,000 -1,000,000 organisms per gram of food is required to cause infection

 Salmonellae grows well on food and can exist for a
considerable period in feces and on pastures.

Question 14

Common food poisoning serotypes

Answer 14

 Some of the salmonella species involved in food
poisoning include; Salmonella typhimurium,
Salmonella enteritidis, Salmonella dublin, Salmonella
softenburg, Salmonella virchow, Salmonella
montevideo, Salmonella infantis, and salmonella
newport.

 These species are also involved in causing diarrhea in animals

Question 15

Heat resistance (Salmonellae)

Answer 15

 The salmonellae are killed by temperatures attained in commercial pasteurization,
 They can remain alive in moist earth for one year and in dry earth for 16 months,
 They are not destroyed in carcasses or offal maintained at chilling or freezing temperatures or in the usual pickling solutions

Question 16

Salmonella food poisoning outbreaks

Answer 16

a) Sporadic cases involving only one or two persons in a household

b) Family outbreaks in which several members of the family are affected

c) Large outbreaks caused by a widely distributed infective food item

d) Institutional outbreaks, which may be caused by a
contaminated single food item.

Question 17

Factors associated with Salmonella food poisoning outbreaks

Answer 17

 Consumption of inadequately cooked or thawed meat or poultry,

 Cross-contamination of food from infected food handlers.

 Presence of flies, cockroaches, rats, in the food environment that act as vectors of the disease.

Question 18

Transmission (Salmonellae)

Answer 18

a) Directly from slaughtered animals to food
b) From human excreta, and transferred to food through hands, utensils, equipments, flies, etc.

Question 19

Foods involved (salmonellae)

Answer 19

 Any food contaminated with salmonellae may be involved.

 However, foods commonly involved are animal derived foods such as:
a. meat and meat products,
b. milk and milk products,
c. egg and egg products

Question 20

Control measures (salmonellae)

Answer 20

 Efficient refrigeration and hygienic handling of food.
 Consumption of properly cooked meat,
 Complete thawing of frozen meats and adequate cooking.
 Heat processing of meat, milk , fish, and poultry to destroy salmonella organisms in food

Question 21

Typhoid and Paratyphoid fever (Enteric fevers)

Answer 21

 Enteric fevers include typhoid and paratyphoid fevers caused by Salmonella typhi and Salmonella paratyphi A, B ,and C respectively.

 The serotypes are similar to other salmonella bacteria, but unlike them, they are essentially parasites of man.

 S. typhi possesses capsular (vi). antigen in addition to the usual O and H antigens found inother serotypes.

Question 22

Disease symptoms (Typhoid and Paratyphoid fever)

Answer 22

 The incubation period is usually 2 weeks, but might vary between 3 and 28 days for typhoid fever and between 1 and 15 days for the paratyphoid fevers.

 The enteric fevers are generalized septicaemicinfections with a frequent, if not constant bacteraemia during the first two weeks of the disease.

 The abdominal symptoms are severe, while fever and illness may continue for 4-6 weeks.

Question 23

Transmission (Typhoid and Paratyphoid fever)

Answer 23

 The typhoid and paratyphoid bacilli are essentially
human parasites and are acquired mostly from human sources, namely, patients and carriers.

 The bacteria can be transmitted by the contamination of water, milk, or food by flies.

 Only a few organisms are needed to cause disease.

Question 24

Control measures (Typhoid and Paratyphoid fever)

Answer 24

 Hygienic control of food and water supplies

 Detection and treatment of chronic carriers

 Vaccination using TAB-vaccine. The vaccine contains a mixed culture of S. typhi, and S. paratyphi. The vaccine protects for 5-7 yrs

Question 25

Campylobacteriosis

Answer 25

 Campylobacter is a group of tiny strictly micro-aerophilic curved or spiral Gram negative rods

 Campylobacter jejuni and Campylobacter coli cause food poisoning and are associated with acute enterocolitis in man.

 Campylobacter jejuni occur in large numbers in cattle feces and poultry as normal flora.

 Campylobacter coli are commonly associated with
human diarrhea.

Question 26

Disease in man (Campylobacteriosis)

Answer 26

 Campylobacter jejuni and C. coli cause illness characterized by diarrhea, abdominal pain, fever, nausea, vomiting, and abdominal complaints.

 The jejunum, ileum, and colon are primarily affected
resulting in acute inflammation and occasionally abscess formation.

 The disease is self-limiting.

Question 27

Mode of infection (Campylobacteriosis)

Answer 27

 Infection occurs by ingestion of campylobacter
organisms in contaminated foodstuffs.

 Foods involved include meat from infected animals,
unpasteurized milk and possibly cross-contamination from these sources to foods eaten uncooked or unrefrigerated.

 Among the meats, poultry constitutes the greatest
potential source of infection to humans.

 Carelessness in the kitchen e.g. cutting chickens with the same knife used to cut other foods without proper cleaning prior to use.

 Pork is a major source of Campylobacter coli.

 Contamination of pork occurs during slaughter.

Question 28

Preventive measures (Campylobacteriosis)

Answer 28

 Thorough cooking of all foodstuffs derived from animal
sources.

 Prevention of re-contamination after cooking.

 Proper refrigeration of foods.

 Recognition, control, and prevention of campylobacter
infections in animals

 Maintenance of high standard of hygiene.

Question 29

Escherichia coli food borne infection

Answer 29

Escherichia coli are potential food poisoning pathogens, which are widely distributed in low numbers in food environments.

Each group is composed of unique O:H serotypes

Each group posses virulence factors characteristic of that group.

The serotypes are characterized by using O-somatic and H-flagella antigens.

Question 30

E. coli strains involved in food borne infection fall into the following groups:

Answer 30

1. Enteropathogenic E. coli (EPEC),
2. Enterotoxigenic E. coli (ETEC),
3. Enteroinvasive E. coli (EIEC) and
4. Enterohemorrhagic E. coli (EHEC).

Question 31

Enteroinvasive E. coli (EIEC)

Answer 31

 A relatively high dose (108 cells) is necessary to produce disease in volunteers.

 The median incubation period is 18 hours (range 2- 48 hrs).

 Food borne spread is the usual mode of transmission.

 Person-to-person spread has also been reported

Question 32

EIEC symptoms

Answer 32

 EIEC strains cause illness that is characterized by watery diarrhea in most patients.

 In addition, there is fever, nausea, and abdominal cramps.

 Bloody diarrhea may occur in fewer than 10% of patients.

 The presence of mucus and polymorphonuclear leucocytes in stool is typical of these strains.

 Illness is usually self-limiting, lasting for 2 to 3 days.

Question 33

Enterohemorrhagic E. coli (EHEC)

Answer 33

 EHEC infection is caused by Escherichia coli serotype O157:H7

Question 34

EHEC Symptoms

Answer 34

 It causes hemorrhagic colitis in humans that is
characterized by diarrhea or abdominal pain, which may be severe and vomiting.

 Few patients develop fever. Illness lasts for 4 to 8 days, although it may extend to 13 days for severe cases.

 Patients with complications have bloody diarrhea, acute ulcerative or ischemic colitis, and sub-mucosal edema with severe colonic inflammation.

Question 35

E. coli O157:H7 characteristics

Answer 35

 The organism E. coli O157:H7 is heat sensitive, but
resistant to freezing.

 It grows poorly at 44oC-45oC, with no growth at 45.5oC, suggesting that its presence may not be detected by fecal coliform assay test.

 Deaths occur in patients who develop hemolytic uremic syndrome (HUS).

 HUS can be recognized by acute renal failure, micro-angiopathic hemolytic anemia, and thrombocytopenia.

Question 36

Control Measures of EHEC

Answer 36

• Proper cooking of hamburger and other meats
• Avoidance of cross-contamination of foods in the kitchen
• Good personal hygiene.

Question 37

Shigellosis (Bacillary dysentery)

Answer 37

 Shigellosis is caused by members of the genus Shigella.

 The species involved include Shigella dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonei.

 All strains of shigella posses potent exotoxins, which are carbohydrate-lipid protein complexes.

 The infective dose is smaller than that of salmonellae, except S. typhi.

Question 38

Transmission (Shigellosis)

Answer 38

 Human cases and carriers are the only important sources of infection.

 Spread is by fecal-oral route, and person-to-person
transmission is common.

 The bacteria leaves the body in stool of an infected person and infects another person through contaminated hands, food, water, or objects (toys, pens, etc).

 Any type of food can transmit the shigella pathogens to cause disease in man.

Flies can spread shigella germs when they get into contact with infected stool and then contaminate drinking water or food.

Shigella organisms may remain viable in tap water for as long as 6 months and in sea water for 2 to 5 months.

Question 39

Preventive measures (Shigellosis)

Answer 39

 Practice good hygiene and sanitation.

 Wash hands well with water and soap each time you use the ablution.

 The home and surroundings should be kept clean to
prevent contamination of food and water supply.

 Proper disposal of human waste or sewage.

 Keep kitchen work surfaces clean.

 Use boiled or chlorinated water

 Eat properly cooked of food

Question 40

Cholera

Answer 40

 Cholera is caused by Vibrio cholera bacterium.

 Cholera vibrios are ingested in drink or food. In natural
infection, the dosage is usually very small.

 The organism multiplies in the small intestine to produce a very potent enterotoxin, which stimulates a persistent out pouring of isotonic fluid by the gut mucosal cells.

Question 41

Transmission (Cholera)

Answer 41

 Man is the only natural host of the cholera vibrios

 Spread of infection is from person-to-person, through contaminated water or foods.

 Shrimps and vegetables are the most frequent carriers.

 Cholera is an infection of crowded poor class communities, and it tends to persist in such areas.

 Cholera outbreaks occur either as explosive epidemics usually in non-endemic areas or as protracted epidemic waves in endemic areas

Question 42

Clinical symptoms (Cholera)

Answer 42

 Cholera is typically characterized by the sudden onset of effortless vomiting and profuse watery diarrhea.

 Vomiting is seen frequently, but very rapid dehydration and hypovolemic shock
.
 The frequent watery stools may be accompanied with small parts of the mucosa being liberated from the intestines.

 Death may occur in 12 to 24 hrs due to rapid dehydration

Question 43

Control measures (Cholera)

Answer 43

1. Provision of potable water
2. Proper sewage disposal
3. Proper cooking and hygienic handling of food
4. Observation of personal hygiene
5. Vaccination

Question 44

Vibrio parahemolyticus foodborne Infection

Answer 44

 Vibrio parahemolyticus is a pathogenic bacterium, whose natural habitat is the sea.

 Human infections occur solely from sea foods such as oysters, shrimps, crabs, lobsters, clams, and related shellfish.

 Cross-contamination may lead to other foods becoming vehicles.

Question 45

Symptoms of the disease ( V. parahemolyticus)

Answer 45

 V. parahemolyticus causes gastroenteritis and extra
intestinal infections in man.

 The mean incubation period is 16.7 hrs (range 3-76
hrs)

 Symptoms include: diarrhea (95 %), cramps (92 %),
weakness (90 %), nausea (72 %), chills (55 %), headache (48 %), and vomiting (12 %).

 Symptoms last from 1 to 8 days with a mean of 4.6 days

Question 46

Vibrio vulnificus foodborne infection

Answer 46

 Vibrio vulnificus causes a severe foodborne infection

 The case fatality rate for V. vulnificus septicaemia
exceeds 50 %.

 In immunocompromised hosts, V. vulnificusinfections can cause fever, nausea, myalgia, and abdominal cramps, 24-48 hours after eating contaminated food.

 The organism can cross the intestinal mucosa rapidly leading to sepsis within 36 hours of the initial onset of symptoms.

 Cases are most commonly reported in warm-weather months and are often associated with eating raw oysters.

Question 47

Listeria monocytogenes infection

Answer 47

 Listeria monocytogenes is a Gram positive bacterium that is pathogenic to both animals and human beings.

 The organism is widespread in nature and is a transient
constituent of the intestinal flora excreted by 1-10% of healthy humans.

 It is extremely hardy and can survive for many years in the cold in naturally infected sources.

Question 48

Vehicle foods (Listeria)

Answer 48

 Listeria monocytogenes occur after consumption of
raw vegetables, salads, raw milk, soft cheese, meat, and meat products.

 Milk, ice cream, cheese, poultry, sauerkraut, salads, sea foods, meat, and meat products contaminated by Listeria.

Question 49

Yersinia Enterocolitica Infection

Answer 49

 This organism has been isolated from beef, lamb, pork, sea foods, vegetables, milk, cakes, and vacuum-packed meat.

 Of all the sources, swine appears to be the major source of strains pathogenic to man.

 Virulence appears to be as result of tissue invasiveness of this organism

Question 50

Yersinia gastroenteritis symptoms

Answer 50

 Symptoms of syndrome develop several days following
ingestion of contaminated foods.

 Symptoms include abdominal pain, diarrhea, fever, vomiting, headache, and pharngitis

 Children appear to be more susceptible than adults

 The organism may be shed in stools for up to 40 days following illness.

Question 51

VIRAL FOODBORNE INFECTIONS

Answer 51

 Viruses are common pathogens transmitted through
food.

 Hepatitis A and Norwalk-like virus (Novovirus) are the most important viral food borne pathogens.

 These viruses are highly i

Question 52

Characteristics of viral food borne infections

Answer 52

 Only a few viral particles are necessary for the disease to develop

 High numbers of viral particles are further transmitted via feces of infected persons (up to 1011 particles per gram of feces).

 Specific lining cells are necessary for virus replication. Accordingly, they can not multiply in foods or water.

 Food borne viruses are relatively stable and acid resistant outside host cells

Question 53

Infectious hepatitis A

Answer 53

 The incubation period is long, being an average of 30 days (range 15-50 days).

 It is a systemic infection characterized by gastrointestinal
manifestations and liver injury, fever, malaise anorexia,
nausea, abdominal discomfort, bile in urine, and jaundice.

 The duration of the disease could be from a few weeks to several months.

Question 54

Norwalk-like virus (Novovirus) food borne infection

Answer 54

 Novovirus infection is relatively mild with an incubation
period of 3 days
.
 Clinical manifestations/symptoms include vomiting and
diarrhea, and rarely convulsions.

 Asymptomatic infection are common and may contribute to the spread of the infection.

 Infections have resulted from the consumption of raw oysters.

Question 55

Norwalk-like virus (Novovirus) food borne infection

Answer 55

 Novovirus infection is relatively mild with an incubation
period of 3 days
.
 Clinical manifestations/symptoms include vomiting and
diarrhea, and rarely convulsions.

 Asymptomatic infection are common and may contribute to the spread of the infection.

 Infections have resulted from the consumption of raw oysters.