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UNIT3 FOOD INTOXICATIONS
Structure
3.0 Objectives
3. 1 Introduction
3.2 Natural Toxins
3.3 Mycotoxins
3.3.1 (^) Aflatoxin 3.3.2 (^) Ochratoxin 3.3.3 (^) Patulin 3.3.4 (^) Alternaria Toxins 3.3.5 (^) Citrinin 3.3.6 (^) Penicillic Acid 3.3.7 (^) Sterigmatocystin 3.3.8 (^) Fusarium Toxins
3 .4 Botulism
3.4.1 Occurrence 3.4.2 Types and Symptoms 3.4.3 Diagnosis 3.4.4 Food Implicated in Botulism 3.4.5 Conditions Necessary for Outbreak 3.4.6 Prevention and Control
3.5 Staphylococcal Food Poisoning
3.5. I Occurrence 3.5.2 Symptoms 3.5.3 Diagnosis 3.5.4 Food Incriminated 3.5.5 Conditions Necessary for Outbreak 3.5.6 Prevention and Control
3.6 Let Us Sum Up
3.7 Key Words
3.8 Answers to Check Your Progress Exercises
3.9 Some Useful Books
3.0 OBJECTIVES
After reading this un it, you will be able to:
- discuss the causal organisms responsible for food borne intoxications;
- explain the toxins production by maid and bacteria (Clostridium botulinum
and Staphylococcus aureus); 47
Introduction • the microbial toxins produced, the foods associated in intoxication, symptoms
of the disease, diagnosis, conditions necessary for outbreak and preventive
measures required will also be discussed; and
- know the naturally present toxins in the food products will also be accounted
for.
After reading this unit you will be able to distingu ish between food borne intoxications
caused by the various microbiological agents and their preventive measures.
3.1 INTRODUCTION
We have already studied about the food borne diseases and their classification.
Food borne intoxications are basically food borne illness caused due to ingestion of
toxin produced my microorganisms (mycotoxins, bacterial toxins). Natural toxins
present in food may also result in food poisoning in humans.
Food poisoning is also caused by consuming old, used, residual, fermented, spoiled,
contaminated. toxic and bacteria infested food.
-----------.,----,--------------
3.2 NATURAL'1'OXINS
Some plants and animals originate food contain toxic substances. Some pulses and
legumes contain a number oftoxic substances such as protease inhibitors, lathyrogens.
and flavism causing agents, cyanogens, haemaglutinins and paponins which are
discussed below:
a) Trypsin inhibitor is a proteinous in nature. It suppresses the release of a 111 ino
acid. It thus interferes with the normal growth of animals fed with such pulses.
b) Haernglutinins are also proteins. They impair the absorption system.
c) Cynogenic glycosides cause cyanide poisoning on hydrolysis of the glycoside
by the enzyme a-glucosidase hydrogen cyanide is liberated. Cyanides content
of 10-20 mg per 10 gm of pulses is considered safe. Many legumes excepting
limabean tPhaseolus lunatus) contain cyanide within these limits.
d) Saponins are glycosides of high molecular weight. It has been reported in
soyabean, sword bean and jack bean. Toxic saponins cause nausea and vomiting
and can be removed by soaking the beans prior to cooking.
e) Alkaloids are known to occur in the seeds of many legumes but they are relatively
innocuous.
1) Some compounds present in pulses appear to bind iodine thus producing a
state of iodine deficiency in the thyroid and eventually goitre,
g) Lathyrism is a disease that paralyses the lower limbs. The disease is associated
with consumption of kesari dal regularly as high as 300g daily. In lathyrism, the
toxic substances interfere with formation of normal collagen fibers in the
connective tissue.
48
h) A hernolytic factor in Vicia faba causes flavism. It is caused by eating
broadbeans or by inhaling pollen of its flowers, Flavism is haemolytic anaemia.
In several cases, death may occur within 24-48 hours of the onset of the attack.
i) Oxalic acid, a constituent of rhubarb, spinach and beet may cause oxalic
poisoning in certain individuals.
Introduction At the beginning of the last century, two major mycotoxicosis caused considerable
suffering and mortality. They were alimentary toxic aleukia (ATA) in Russia, caused
by consumption of corn contaminated with T-2 toxin produced by Fusarium
sporotrichoides and yellow rice disease in Japan, associated with Penicillium
islandicum. More recently, outbreaks ofaflatoxicosis caused by consumption of
corn contaminated with Aspergillusflavus were reported from India involving
approximately 1000 people of whom nearly 100 died.
Several very important mycotoxins such as the sporidesmins, sJaframine and
tremorgens are associated with animal feeds and forages that affect the quality of
meat and other animal products. It is also seen that mycotoxins present in animal
feed get into human foods because they pass through the food chain in either their
original or metabolized form.
When we store foods under inappropriate conditions they are susceptible to mold
growth. Many mycotoxigenic species are able to produce several mycotoxins. It is
likely, therefore, that contaminated foods will contain a cocktail of toxins that can
interact synergistically.
Some. major mycotoxins found in foods
Mycotoxin Major Foods Common Producing Species
Aflatoxins Corn, groundnuts. figs, Aspergillusflavus.^ A.
tree nuts parasiticus
Aflatoxin M\ Milk, milk products (secreted by cow after
metabolism of Aflatoxin B)
Deoxynivalenol Cereals Fusarium graminearum, F
culmorum
Fumonisin Corn Fusarium moniliforme
Ochratoxin Corn, cereals, coffee Penicillium verrucosum,
beans Aspergillus ochraceus
Patulin Applejuice Penicillium expansum
Sterigmatocystin Cereals, coffee, beans, Aspergillus versicolor
cheese
Zearalenone Corn, barley, wheat Fusarium graminearum
3.3.1 Aflatoxin
Aflatoxins are the most widely studied of all mycotoxins. Knowledge of their existence
dates from 1960, when more than 100,000 turkey died in England after eating
peanut meal imported from Africa and South America. From the poisonous feed
were isolated Aspergillus flavus and a toxin produced by th is organ ism that was
designated aflatoxin tAspergillusflavus toxin- A-fla-toxin). These compounds are
highly substituted coumarins, and at least 18closely related toxins are known. Aflatoxin
B\ is the most important of this large family of compounds and is produced by
Aspergillus flavus, A. parasiticus and A. nominus. The toxicity of the six most
potent aflatoxins decreases in the following order: B?M?G ,>B:>M 1 ?G 2.
Occurrence: Aflatoxigenic molds can occur in wanner parts of the world and
aflatoxicosis maybe produced in a wide range of tropical and subtropical food
commodities such as figs, tree nuts and cereals. The most important crops are corn and groundnut, but it can also occur in temperate crops such as wheat. Although the production of aflatoxin initially was considered to be a problem in post harvest crops stored at inappropriate temperatures and water activities, it is now known
that these compounds can be present in the field before harvest. A.flavus and A.
parasiticus may infect healthy plants at a very early stage.
Biological effects: Aflatoxins are acute hepatotoxins and are known to be carcinogenic in some animal species as rat. Aflatoxin B, is acutely toxic and is responsible for liver necrosis. The toxicological effects of the atlatoxins are intluenced by their metabolism after intake into their body (Figure 10.1).
Food Intoxications
Aflatoxin
B,
Aflatoxin M, ~ Milk I
Aflatoxin epoxide Dihydroxy aflatoxin
A~I
Figure 3.1: Representation ofthe metabolism of aflatoxin and its biological effects When cows eat feed containing aflatoxin, aflatoxin M, and M2 is excreted in the milk. Although M, and M2 are less toxic than the parent compound BI' M, retains
its toxic and carcinogenic ability in many animals. The LD50 of AFB, for rats by the
oral route is l.2mg/kg and 1.5 to 2.0 mg/kg for AFG r
Control: Because atlatoxins are potentially widespread in occurrence and have an insidious combination of acute and chronic toxicity, it is prudent to control their presence in food. Many countries have legislation establishing maximum tolerance levels. Chemically treating the atlatoxin contaminated commodities like nuts maybe possible or to use technologically sophisticated equipment to sort and discard the contaminated units. It may also be possible to control the production ofatlatoxin in the field by an integrated programme of agricultural management that may include plant breeding, improved irrigation and replacement of atlatoxigenic strains by non-
atlatoxigenic strains of A.flavus.
Check Your Progress Exercise 1 Note: a) Use the spaces given below for your answers. b) Check your answers with those given at the end of the unit.
- What are mycotoxins? How are they harmful?
3.3.3 Patulin Food^ Intoxications
It is a toxic and antibiotic metabolite produced by several species of Penicillin.
Aspergillus and Paeciliomyces but the most important in the context of human
food production is P expansum, a soft rot pathogen of apple and pears. Patulin is
unsaturated lactose and is sensitive to sulphur dioxide and is unstable in alkali but
stable in acid.
Occurrence: It is found in a range of foods based on fruits. Presence of patulin in
fruit juice is a indication thatthe juice was extracted from poor quality fruit which is
undesirable and should be avoided with good manufacturing practices. This mycotoxin
has also been found in moldy bread, sausage, fruits (including bananas, pears,
pineapples, grapes and peaches) and other products.
Biological activity: Patulin has an acute oral LDsc in rodents of about 30-50 mg/
kg and has been shown to be teratogenic, immunotoxic and neurotoxic and to cause
gastrointestina! disturbances in rats. Patulin is quite rapidly excreted from animals. It
causes chromosomal aberrations in animal and plant cells and is a carcinogen.
Control: In apples molded by Penicillium expansum, most ofthe patulin is confined
to the region of damaged tissue and simply removing the lesions reduces the toxin by
90%, but if Icm around the lesion is also removed, no patulin is detectable in rest of
the apple. Ascorbic acid has been reported to reduce levels of patulin. Although
pasteurization (using high temperature, short time treatment often seconds at 90°C)
causes some reduction in patulin in fruit juices, it is only of the order of20%, which
is not sufficient to make a badly contaminated food product acceptable.
3.3.4 Alternaria Toxins
Several species of Alternaria (A. citri, A. alternata, A. solani and A. tenuissimai
produce toxic substances that have been found in apples, tomatoes, blueberries and
others. The toxins produced include alternariol, alternariol monomethyl ether,
altenuene, tenuazonic acid and altertoxin-l.
3.3.5 Citrinin
Penicillin citrinum. P viridicatum and some other fungi produce this mycotoxin.
It has been recovered from polished rice, moldy bread, country cured hams, wheat,
oats, rye and other si 111 ilar products. It is a known carcinogen.
3.3.6 Penicillic Acid
This mycotoxin has biological properties similar to patulin. It is produced by a large
number offungi, including many Penicillia as well as members oftheA. ochraceus.
One of the best producers is P cyclopium, it has been found in corn, beans and
other field crops. Its LDso in mice by subcutaneous route is 100 to 300 mg/kg and
it is a proved carcinogen.
3.3.7 Sterigmatocystin
These mycotoxins are structurally and biologically related to the aflatoxins, and like
the latter, they cause hepatocarcinogenic activity in animals. Among the organisms
that produce them are Aspergillus versicolor, A. nidulans, A. rugulosus. The
LD50 for rats by intra-peritoneal injection is 60 to 65 mg/kg.
3.3.8 Fusarium Toxins
Another important genus ofmycotoxin producers is Fusarium, many species of
which produce members ofthe trichothecene family ofmold metabolites like
deoxynivalenol, neosolaniol and T-2 toxin etc. 53
Introduction (^) Deoxynivalenol
Deoxynivalenol (DON) is a far more common, but much less toxic, trichothecene
and is produced by species such as F graminearum and F culmorum. LD 50 of
DON is 70mglkg. The trichothecenes are remarkably stable compounds, and DON
will survive both dry milling and wet milling processes of corn. The baking of bread
has relatively little effecton trichothecenes such as DON.
Zearalenone
It was first isolated as the agent responsible for vulvovaginitis in pigs has very little
acute toxicity, but there should be some concern about chronic exposure to a
compound known to be estrogenic. It may be produced, together with DON and
other trichothecenes, in a wide range of cereals includ ing corn, barley and wheat.
Moniliformin
It was first obtained from a strain of Fusarium moniliforme isolated from southern
leafblight- damaged corn seed as a water soluble toxin. The LDso for mice has been
reported to be 20.9 mg/kg for females and 29. I mg/kg for males. At toxic doses
moniliformin causes rapid death without obvious overt cellular damage, although
acute degenerative lesions in the myocardium are reponed.
Fumonisins
The most recently characterized mycotoxins of any major significance in human
health are the fumon isins produced by species of Fusarium, such as F moniliforme.
Like a number of my cot ox ins, the fumonisins are relatively heat stable and would
not be significantly destroyed by drying processes for corn or heat treatments used
for the production of maize derivatives. Fumonisin BI is water-soluble is known to
be responsible for equine encephalomalacia, porcine pulmonary ederna syndrome
and hepatic cancer in rats and maybe involved in the epidemiology of esophageal
carcinoma in humans in southern Africa and parts of China.
The range of regulatory limits for mycotoxins
Mycotoxin Regulatory Limit (Ig/kg)
A t1atoxins in foods 0-
At1atoxin M 1in milk 0-0.
Deoxynivalenol in wheat 1000-
Ochratoxin A in foods 1-
Patulin in apple juice 20-
Zearalenone 30-
3.4 BOTULISM
Botulism (Latin botulus, sausage) is a neuro-paralytic disease caused by the ingestion
offood containing the neurotoxin produced by Clostridium botulinum,
3.4.1 Occurrence
Clostridium botulinum is an anaerobic, Gram-positive, spore forming, rod shaped
bacteria that produces the potent neurotoxin. The organism and its spores are widely
Introduction 3.4.4 Foods Implicated in Botulism
The types offoods 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. Botulinal toxin has been demonstrated in a considerable variety
of foods, such as canned corn, peppers, green beans, soups, asparagus, mushrooms)
spinach, tuna fish ham, sausage and smoked and salted fish.
3.4.5 Conditions Necessary for Outbreak
The following conditions are necessary for an outbreak of botulism:
1. Presence of spores of C. botulinum of type A, B or E in foods being consumed
or being processed in some other way
2. A food in which the spores can germinate and the clostridia can grow and
produce toxin
3. Survival ofthe spores ofC botulinum because of inadequate heating in canning
or inadequate processing otherwise
4. Environmental condition after processing that will permit germination of the
spores and growth and toxin production by the organism
5. Insufficient cooking of the food to inactivate the toxin
6. Ingestion of the toxin-bearing food
3.4.6 Prevention and Control
The prevention and cure of botulism involves:
1. Strict adherence to safe food-processing practices by the food industry
2. Educating the public on safe home-preserving (canning) methods for foods
3. Not feeding honey to infants younger than 1year of age
4. Not tasting any processed food having a questionable odour
5. Recommended treatment for botulism includes early administration of botulinal
antitoxin and intensive supportive care (including mechanical breathing
assistance).
Check Your Progress Exercise 2
Note: a) Use the spaces given below for your answers.
b) Check your answers with those given at the end of the unit.
I. What are the causative organism and the foods associated with botulinal food
intoxication?
2. Differentiate between adult and infant botulism .. Food^ Intoxications
3. List down the various mycotoxins associated with food.
3.5 STAPHYLOCOCCAL FOOD POISONING
Staphylococcal food poisoning results from consumption of food containing·
enterotoxin produced by enterotoxigenic strains of Staphylococcus aureus. It is
caused by ingestion of improperly stored or cooked food.
S aureus is a Gram-positive coccus, very resistant to heat, drying and radiation. If
the bacteria are allowed to incubate in certain foods, they produce heat-stable
enterotoxin that renders the food dangerous. Six different enterotoxins have been
identified and are designated as A, B, C, D, E and F.
3.5.1 Occurrence
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. Staphylococci are present in the nasal passages and throats and on the
hair and skin of 50 percent or more of healthy individuals. A wide range offoods
maybe involved in Staphylococcal food poisoning including ham, turkey, chicken
and chicken salad, baked products, especially filled pastries, table ready-meats
(sausage etc.), precooked frozen foods and dairy products.
S aureus cells are relatively more resistant than many gram negative food spoilage
organisms. Human intoxication is caused by ingestingenterotoxins produced in food
by strains of S aureus, usually because the food has not been kept hot enough
(60De, or above) or cold enough (7.2De, or below). In frozen foods they may
survive even at-lODe. In general, survival ofS aureus is best in foods that contain
high concentration of sugars, eggs and buffering component such as phosphates and
protein. Salt concentration less than 9.5%, temperature more than 20 De and a pH in
the range 6-8 are favourable for growth and enterotoxin formation.
Check Your Progress Exercise 3
Note: a) Use the spaces given below for your answers. b) Check your answers with those given at the end of the unit.
- What are the conditions favouring the outbreak of Staphylococcal food poisoning?
Food I ntnx icat iun:
- Give the preventive and control strategies of Staphylococcal food poison ing.
3.6 LET US SUM UP
The unit dealt with the food borne intoxications that are caused by ingestion of toxins produced from molds (Aspergillus niger, Penicillium sp.) or bacteria (c. botulinum and S. aureus'y. An effort has been made to point out the major conditions required for outbreak of the disease along with the diagnosis and the preventive measures requ ired to prevent the outbreak of disease.
3.7 KEYWORDS
Food Borne Intoxication
It is the food borne disease caused due to ingestion of food containing the toxin. Mycotoxins These are secondary metabolites produced by filamentous fungi on food and feed that cause illness and death when ingested by man or animals.
Ochratoxin
Mycotoxin elaborated by Aspergillusflavus.
Mycotoxin produced by Penicillium verrucosum.
Aflatoxin
Patulin Mycotoxin produced by species of Penicillium. Aspergillus and Paeciliomyces.
Citrinin Mycotoxin produced by Penicillin citrinum.
. Introduction Botulism Food borne^ intoxication^ caused^ due to consumption^ or food containing toxin. produced by Closinduun botulinum.
Staphylococcal Food Poisoning
Food borne intoxication caused due to consumption or food containing toxin. produced by Staphylococcus aureus.
LDso Dose Lethal^ Dose^ of toxin^ at which^ minimum^ 50%^ of the
population may get in fcctcd by the taxi".
Zcaralenone Mycotoxin produced by F1IsariuI1I graminearum and F tricinctum.
3.8 ANSWERS TO CHECK YOUR PROGRESS EXERCISES
Check Your Progress Exercise 1
1. • Mycotoxins are toxins (secondary metabolitcs) produced by filamentous
fungi on food and feed that cause illness when ingested
- Cause hepatotoxicosis. carcinogenesis, liver cirrhosis etc.
- Biological effects of aflatoxin include hepatotoxicosis, carcinogenesis and liver cirrhosis.
- Natural toxins in roods: Trypsin inhibitor. haernaglutenins. cyanogenic glycosides. saponins, alkaloids, goitrogens.
Check Your Progress Exercise 2 I. • (^) Botulism is caused by the bacteria Clostridium botulinum.
- All low acid roods can support growth and toxin production by Clostridium botulinum.
- Unheated foods are causative agents e.g.: canned foods (canned corn. peppers, green beans. soups), sausages, smoked fish etc.
- • Adult Botulism is prevalent amongst adults whereas Infant Botu lism is prevalent in in fants of less than one year of age.
- Caused due to ingestion of viable spores 0 f c. botulinum.
- Symptoms in adults: Nausea, vomiting, fatigue, dizziness, headache. dryness of skin and respiratory failure
- Symptoms in in fants: Constipation, weakness and loss of appetite and in severe cases death
- Mycotoxins associated with foods are:
- Af1atoxins (produced by Aspergillusflavusi
- Ochratoxin (produced by Penicillium verrUCOSlIl11)
- Patulin (P expansum)
60 •^ Citrin in^ (Penicillin^ citrinumi
