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D. Mona Othman Albureikan
Food Hazard & Non-bacterial
Agents of Foodborne Illness
- Food are complex mixtures of chemicals which
contain compounds that potentially harmful as well as
those that are beneficial.
- A simple insufficiency will lead to so many diseases
such as goiter (iodine deficiency), pellagra (nicotinic
acid), beriberi (thiamine) and scurvy (ascorbic acid).
- Several vitamins are toxic if consumed in excessive
-Green potatoes and potato sprouts contain the toxic
alkaloid solanine which should be avoided.
- Legumes or pulses contain a number of anti-
nutritional factors such as phytate, trypsin inhibitors
and lectins (haemagglutinins).
- Many of these are destroyed by normal preparation
producers such as soaking and cooking.
Possible causes of foodborne illness
- Chemical-Intrinsic ( natural
- Red kidney bean poisoning,
- Algae (paralytic shellfish
-Bacteria (infection and
- Fungi (mycotoxins).
- Parasite, Protozoa,Viruses.
World Health Organization (WHO)
-Foodborne disease has been defined by the World
Health Organization (WHO) as: any disease of an
infectious or toxic nature caused by
food or water.
-The WHO expert pointed out that
foodborne disease ( microbial origin )
are the most widespread problem in the contemporary
world and the cause of reduced economic productivity.
Risk Factors Associated With
Factors contributing to outbreaks of food poisoning:
1. Storage at ambient temperature. 2. Inappropriate cooling.
3. Contaminated processed food 4. Undercooking
5. Contaminated canned food 6. Inappropriate thawing
7. Cross contamination 8. Infected food handlers
The Site of Foodborne Illness.
- The digestive tract: the
producing) effect occur by
giving rise to symptoms such
as diarrhoea and vomiting.
- In the mouth, food is mixed
with saliva and broken down
mechanically to increase the
surface area available for
attack by digestive enzyme.
-Saliva is an alkaline fluid containing starch-degrading
(amylase) enzyme and the antimicrobial factors
lyzozyme, lactoferrin and
-It provide assist chewing
and swallowing and performs a cleansing function, rising
the teeth and mouth to remove debris.
The Site of Foodborne Illness
* In the stomach, food is blended with gastric juice, an
acidic fluid containing hydrochloric acid that kill most of
the micro-organisms but their spores survive.
* In the small intestine most of the digestion and absorption
of food occur.
* In the healthy individual, the micro flora of the small
intestine is mainly comprised of lactobacilli and
streptococci, although , other bacteria have the ability to
colonize the epithelium and cause illness as a consequence.
The Site of Foodborne Illness
Non-bacterial Agents of
- Helminths, nematodes, protozoa, viruses and
toxic metabolites of fungi and algae.
Helminths & nematodes
-There are number of animal parasites which can
be transmitted to human via food and water.
- These complex animals do not multiply in foods
and they can not be detected and enumerated by
cultural methods in the way that many bacteria
- There presence is detected by direct
microscopic examination often following some
form of concentration and staining procedure.
Platyhelminths: liver flukes and
-The two most important classes of the Platyhelminths
(flatworms) are the Trematoda, which includes the liver
fluke Fasciola hepatica , and the cestoda which includes
tapeworm s of the genus Taenia.
- These organisms have complex life cycles which may
includes quit unrelated hosts at different stages .
Perhaps the most notorious of the nematodes in
the context of foodborne illness and the only one
is trichinell spiralis , the agent of trichinellosis .
This parasite has no free-living stage but is
passed from host to host which can include a wide
range of mammals including humans and pigs .
Thus trichinellosis in the human population is
usually acquired from the consumption of infected
raw or poorly cooked pork products.
The presence of these
parasite in animals
usually gives rise to
macroscopic changes in
tissues and organs which
can be recognized by
meat inspection after
-Amongst the protozoa only a few genera are of special
concern to the food microbiologist ; the flagellate Giardia,
the amoeboid Entamoeba (histolytica) and
three sporozoid genera Toxoplasma,
Sarcocystis and cryptosporidium.
found on salad vegetables and fruit and
could occur on any foods which are
washed with contaminated water or
handled by persons not observing good
A number of planktonic algae can produce very toxic
compounds which may be transported to filter-feeding
shellfish such as mussels or small herbivorous fish which
are food for larger carnivorous fish. These toxins pass to
human by consumption which are most toxic.
• PSP (paralytic shellfish poisoning) NSP (neurotoxic
shellfish poisoning) .
•* The toxins implicated in the various forms of shellfish
poisoning are not only undetectable organoleptically but
are also generally unaffected by cooking.
-The genus Alexandrium are the best known of a number
of dinoflagellates responsible for paralytic shellfish
-The toxic metabolites of these
algae, which includes saxitoxin
and gonyautoxin block the nerve
transmission causing symptoms
such as tingling and numbness of the fingertips and lips,
and respiratory paralysis.
Several genera of
,especially species of
reservoirs and may cause
deaths of animals
drinking the contaminated
It is the ability of some moulds to produce toxic
metabolites, known as mycotoxins, in foods and their
association with a range of human diseases, from
gastroenteric conditions to cancer.
Mycotoxins of Aspergillus ( Aflatoxin is not only acutely
toxic but, for the rat, it is amongst the most
carcinogenicity compounds known).
Maycotoxins of Penicillum ( Beriberi )
Mycotoxins of Fusarium ( Some species of fusarium cause
economically disease of crop plants).
Three of the most
- T-2 toxin.
but react differently
against the immuno
Food borne viruses
- As obligate intracellular parasites, viruses cannot
Multiply other than in a susceptible host cell
In recent years viruses have been recognized as an
important cause of food borne illness.
The only virus known to be
food borne. Polio can be
incubation period of 3-5 days
and characterized by headache,
fever and sore throat
contaminated milk had been the
principal source of foodborne
polio but this route of infection
had controlled by
improvements in hygiene
Hepatitis A and E
-Hepatitis A, the cause of infectious hepatitis.
-The incubation period varies between two and six
-During this period the virus
multiplies in the cells of the
gut epithelium before it is
carried by the blood to the liver.
-Hepatitis E virus, it has unusual (RNA) structure.
- It is transmitted by the oral and produces illness after
an incubation period of 40 days.
-A number of different viruses have been implicated in
gastroenteritis by their presence in large number in
- Food borne viral gastroenteritis is characterized by an
incubation period of 15-50h followed by diarrhoea and
vomiting which persists for 24-48 h.
- Enteric viruses may be introduced into foods either as
primary contamination, at source where the food is
produced, or as secondary contamination during handling,
preparation and serving.
-An interesting approach is to use coli phage, a
bacteriophage which infects the enteric bacterium e. coli,
as a viral indicator.
- Coliphages do not require expensive
tissue culture techniques for their
enumeration since they can be detected
through their ability to from plaques in
culture of a suitable strain of e. coli.
- The problem of extraction of the coli
phage from food remain .
-Spongiform encephalopathies are degenerative
disorders of the brain that occur in a number of species.
- They are recognized by the
clinical appearance of the
affected animal and the
histological changes they
produce in the brain.
shows vacuoles in the neurons giving the grey matter
the appearance of a section through a sponge
-Scrapie,The disease of sheep and goats.
-Its name is derived from one of the symptoms an itching
which causes the infected animal to scrape itself against
• The agent of scrapie has
described as slow viruses
Due to their long
• It is now known as a prion.
• It is contain no nucleic acid.
• It is neither a bacterium nor a
• It is invisible in the electron
• Cannot be cultured in media or
cell cultures. and does not
stimulate the formation of
specific antibodies in infected
1- James M. Jay. (2013). Modern Food
Microbiology . Springer; Softcover reprint of
the original 1st ed. 1996 edition (April 26,
2- Martin R. Adams and Maurice O. Moss.
(2007). Food Microbiology. Royal Society of
Chemistry, Thomas Graham House, Science
Park, Milton Road, Cambridge CB4 0WF, UK.
September 11, 2007.
3- Some pictures from different sits.