Download Chapter 10–Food Microbe

Food borne Illness
Objective
 -Food borne ilness
 Food Intoxication---def, example
 Food infection---def, example
Food borne Illness
 Microorganisms enter the gastrointestinal tract in
association with ingested food and water.
 Two distinct processes that can initiate disease
through intestinal tract are food
poisoning/intoxication and food infection.
1. Food Intoxication
 Food borne 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 occurs after food is ingested.
Characteristics of food poisoning
Toxin is produced by a pathogen while
growing in a food.
II. A toxin can be heat labile or heat stable.
III. Ingestion of food containing active toxin (not
viable microbial cells) is necessary for
poisoning.
IV. Symptoms generally occur quickly, as early as
30 minutes after ingestion.
I.
Characteristics of food poisoning--Cont
V. Symptoms differ with types of toxin;
enterotoxins produce gastric symptoms and
neurotoxins produce neurological symptoms.
VI. Febrile symptom is not present.
(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.
Staphylococcal Intoxication--Cont
 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.
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).
Characteristics of
Cont
bacteria--
 Main source of contamination is man. Others are
animal.
 Personal hygiene of food handler is important. Avoid
disease person from preparing food.
(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 C. 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.
Botulism--Cont
Sources: soil, sewage, mud, sediments, lakes
Botulism--Cont
 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.
Botulism--Cont
 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.
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.
Characteristics of
Cont
bacteria--
 Since it is a highly potent toxin, only a very small
amount necessary to cause severe symptoms and even
death (1 ng/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.
Characteristics of
Cont
bacteria--
 Since it is a highly potent toxin, only a very small
amount necessary to cause severe symptoms and even
death (1 ng/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 underheating and
leakage.
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.
Food
Cont
Infection--
 The factors which influence the infection and
infective dose are:
 Organisms virulence
 Host resistance
 The buffering capacity of the food ingested
Characteristics of food borne
infection
 Live cells of the enteric pathogens must be consumed through
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food.
The pathogens penetrate through the membrane and establish in
the epithelial cells of the intestines, multiply and produce toxins.
Dose levels to cause infection vary greatly from 10 extremely
virulent cells to about 10^5 cells or more.
Symptoms generally occur after 24 hours.
Enteric symptoms are local and due to enteric infection and the
effect of toxins such as diarrhea, nausea, vomiting and fever.
Nonenteric symptoms occur when the pathogens or their toxins
pass through the intestine and invade other intestinal organ and
tissue.
(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 105-106 cells.
 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.
Characteristics of bacteria
 Mesophilic, gram negative, nonsporulating, facultative
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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.
Characteristics of
Cont
bacteria--
 It can cause inflammation of the intestinal tract,
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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.
(b) Shigellosis (Bacillary dysentery)
 Bacillary dysentery ---An acute infection of the
intestine by shigella bacteria; characterized by
diarrhoea and fever and abdominal pains
 The genus Shigella contains four species: S. flexneri, S.
dysenteriae, S. bodyii, S. 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.
Characteristics of bacteria
 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.
 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.
Characteristics of
Cont
bacteria--
 The infective dose is very low(101-103). 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 causing
abdominal pain, diarrhea often mixed with blood,
mucus and pus, fever, chills and headache.
CLOSTRIDIUM PERFRINGENS
Foods involved
Contaminated poultry meat and meat products, especially
stews, gravies and pies.
Main Symptoms
Abdominal pain, diarrhoea and nausea.
Onset of Illness
8 to 22 hours, (usually 10 to 12 hours).
Source
This organism is found in the waste of animals and man, and
often in raw meat and in soil.
It thrives in airless conditions and survives ordinary cooking.
CAMPYLOBACTER
Foods involved
Contaminated meat and meat products, especially
poultry.
Contaminated water, and raw milk.
Main Symptoms Diarrhoea, abdominal pain, fever, nausea, and vomiting.
Onset of Illness
1 to 10 days (usually 3 to 5 days).
Source
Campylobacter bacteria are often present in the waste of
man and animals (especially domestic animals and
poultry).
This illness is infectious and can be spread to other
people.
LISTERIA
Foods involved
Main
Symptoms
Contaminated processed meats and meat products, raw
milk, seafood, poultry and vegetables etc (eg coleslaw).
Normal host
Acute/mild fever, influenza-like
symptoms.
At risk host
Fever, intense headache, nausea,
meningeal irritation and vomiting.
Infection of the foetus, septicemia,
meningitis, and still-birth.
Onset of Illness 3 days to 3 weeks.
Listeria bacteria are commonly found in soil, water,
Source
vegetation, domestic animals, and man.
The illness, though infectious, is relatively rare.
Pregnant women, the elderly, and those with lowered
At Risk Hosts
immune systems.
Virus
 Not much related to food…but research shows that certain
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virus can cause illness.
Reason:
Obligate parasite---need host
Do not grow in culture media
To culture need tissue---cells…procedure is lengthy and
need trained personell.
Because virus do not replicate in food, their number is may
be expected to be low relatively to bacteria.
Laboratory virology technique are not practice in many
food miocrobe lab.
Virus
 Example of virus known to infect food such as:
 Hepatitis A virus –Mode of transmission---fecal and
oral route
 Have single stranded RNA
 Incubation period for infectious hepatitis ranges from
15 to 45 days.
 Oral route is the mode of transmission---transmission
from raw or partially cooked shellfish from polluted
waters.
 Norwalk virus—Is a small, round structural viruses
(SRSVs).
 The virus was first recognize in a school outbreak in
Norwalk, Ohio.
 Cause gastroenteritis.
Conclusion
 Next lecture: Beneficial Uses of Microbe.