Foodborne illnesses

1. Foodborne Illnesses

2. Foodborne Illnesses
 Microorganisms enter the gastrointestinal tract in
association with ingested food and water.
 Two distinct processes that can initiate disease
through intestinal tract are:-
 Food intoxication
 Food infection

5. 1. Food intoxication
 Foodborne intoxication or food poisoning of microbial origins occurs from the ingestion of food
containing preformed toxin.
 Due to production of toxin by the bacteria in the food. The bacteria usually do not grow in host.
Intoxication occur after food ingested.
 Some general characteristics of food poisoning includes:
a. Toxin is produced by a pathogen while growing in a food.
b. A toxin can be heat labile or heat stable.
c. Ingestion of food containing active toxin (not viable microbial cells) is necessary for poisoning.
d. Symptoms generally occur quickly, as early as 30 minutes after ingestion.
e. Symptoms differ with types of toxin; enterotoxins produce gastric symptoms and neurotoxins
produce neurological symptoms.
f. Febrile symptom is not present.

7. (a) Staphylococcal intoxication
 Enterotoxigenic strains of S.aureus produce six different enterotoxin
(A, B, C1, C2, D, and E) in many types of food. All these toxins vary
in heat stability and the strength/potency.
 Contaminated food do not have a distinct smell or taste unless
hundreds of million present. Some of the foods that are frequently
implicated are corned beef, salami, barbecued meat, salads, baking
products.
 Staphylococci toxins are enteric toxins and cause gastroenteritis.
Symptoms such as nausea, vomiting, abdominal pain and diarrhea
(1/3 of patient). Some secondary symptoms are sweating, chills,
headache and dehydration. The disease lasts for about 1-2 days and
is rarely fatal.
 The symptoms may occur within 2-4 hours after foods are ingested.

8.  Characteristics of bacteria:
Coccus, gram positive, non-motile, facultative anaerobe,
the cells clump together like grapes. Grow well in foods
containing 10% salt solution. Dissolve gelatine and
produce heat stable toxin. Non capsule, non sporulating
and non motile.
 If there is good intoxication by this microorganisms it is
possible that the toxin is present in food but the bacteria
might have been destroyed during processing heating.
 Main source of contamination is man. Others are animal.
Personal hygiene of food handler is important. Avoid
disease person from preparing food.

9. (b) Botulism
 Very rarely but once happen mortality rate is high. Botulism results from
consumption of foods containing the toxin botulin produced by Clostridium
botulinum.
 Spores of Clostridium botulinum is widely distributed in soil, sewage, mud,
sediments, lakes etc. Fruits and vegetables can be contaminated with
spores from soil, fishes from water and sediments and various other foods
from any of the above sources.
 The botulin toxin are neurotoxic toxin produced disturb the peripheral nerve
at the central nervous system. Following ingestion, the toxins are absorbed
through the intestinal wall and reach the nerve cells, stopping the signal
transfer and causing paralysis of involuntary muscle.
 Neurological symptoms includes vomiting, ocular paresis (difficulty in moving
eye), dilopia (double vision), paralysis of pharynx, sore throat, difficulty in
swallowing, breathing, speaking, dryness of the mouth and paralysis of
different involuntary muscles that spread to the lungs and heart. Death
usually results from respiratory failure.

10.  Characteristics of bacteria:
The microorganisms is an anaerobe, gram positive, rod/club shape,
motile, heat resistant and form single terminal spore (very resistant to
heat). There are 6 strains (type A, B, C, D, E, and F)
 Cells are sensitive to low ph (<4.6), lower Aw (<0.93) and moderately
high salt (5.5%) therefore it does not produce toxin in acidic food.
Only can produce toxin if pH is more than 4.6 and thus it is not a
problem in acidic food.
 Since it is a highly potent toxins, only a very small amount necessary
to cause severe symptoms and even death (1 mg/kg body weight).
Nevertheless, the toxin are relatively thermolabile i.e. easily
inactivated by heat (80ºC for 30 min)
 More than 90% of botulism cases are caused by homemade canned
food due to under heating and leakage.

11. 2. Food infection
 Ingestion of food containing pathogenic enteric
microorganisms. The microorganisms grow within the
body and cause infection/poisoning.
 Generally establishment of infection requires a relatively
high infective dose.
 The factors which influence the infection and infective
dose are:
 Organisms virulence
 Host resistance
 The buffering capacity of the food ingested

12.  Some characteristics of foodborne infections include:
a. Live cells of the enteric pathogens must be consumed through food.
b. The pathogens penetrate through the membrane and establish in the
epithelial cells of the intestines, multiply and produce toxins.
c. Dose levels to cause infection vary greatly from 10 extremely virulent
cells to about 10^5 cells or more.
d. Symptoms generally occur after 24 hours.
e. Enteric symptoms are local and due to enteric infection and the effect of
toxins such as diarrhea, nausea, vomiting and fever.
f. Nonenteric symptoms occur when the pathogens or their toxins pass
through the intestine and invade other intestinal organ and tissue.

13. (a) Salmonellosis
 Salmonellosis is a zoonosis i.e. disease transmissible between
human and animal. It is still the leading cause of foodborne
disease.
 The disease occur due to ingestion of Salmonella enteritidis at
about 10^5-10^6 cells.
 Characteristics of this bacteria are mesophilic, gram negative,
nonsporulating, facultative anaerobe, motile rods. Gas
formation when grow in glucose broth but not lactose, utilize
citrate as carbon source, produce hydrogen sulphide, do not
produce indole and negative for ureases. They are killed by
pasteurization, sensitive to low pH and do not multiply at low
Aw (<0.94)
 Salmonellae are natural inhabitants of the gastrointestinal
tracts of domestic animals. Human can be carriers following
an infection and shed the pathogens through feces for a long
time.

14.  It can cause inflammation of the intestinal tract,
abdominal cramps, diarrhea, nausea, vomiting, chills,
fever and prostration. Feces may contain blood and in
serious case, dehydration can occur.
 Following ingestion, the pathogens invade mucosal layer
and produce thermolabile toxin which results
inflammation and accumulation of water in the intestine.
 The ability of the pathogens to damage the cells is also
attributed to the production of a thermostbale cytotoxic
factor. Incubation period within 8-36 hours and the
symptoms can last up to 3 days.

16. (b) Shigellosis
 The genus Shigella contains four species: Shi. flexneri,
Shi. dysenteriae, Shi. bodyii, Shi. sonnei.
 Only humans and some primates are their hosts. The
organisms are either transmitted directly through fecal-
oral routes, or indirectly through fecal contaminated food
and water.
 The cells of the species are gram negative, non motile.
Facultative anaerobes, rod shaped, catalase positive,
oxidase and lactose negative and also fermenting sugars
without gas.

17.  The strains are believed to carry plasmid encoded invasive traits that
enable them to invade epithelial mucosa of the small and large
intestine.
 Once engulfed by the epithelial cells. They are capable of producing
an exotoxin that has the enterotoxigenic properties which is called as
Shiga toxin.
 The infective dose is very low(10^1-10^3). Symptoms occur within 1-
3 days after contaminated food ingested.
 An infected person may shed the pathogens long after the symptoms
have stopped.
 The symptoms resulted from both the invasiveness of epithelial
mucosa and the enterotoxin therefore abdominal pain, diarrhea often
mixed with blood, mucus and pus, fever, chills and headache.