Transcript 06. Thamina food poisioning2010-10

Gastroenteritis &
Food Poisoning
Dr . Thamina Sayyed
Registrar – Microbiology
KKUH
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Gastroenteritis
Syndromes of diaeehea & vomiting that tend to involve non
infalmmatory infection in the small bowel or
inflammatory infection of large bowel.e.g E.coli.Yersinia
campylobacter,clostridium,cryptosporidium,cyclospora.rotavirus
etc
Foodborne Diseases
Apply to illnesses acquired by consumption of
contaminated food.
Sometimes incorrectly referred to as food poisoning.
Includes :
foodbornee intoxications
foodbornee infections.
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There are two types of food poisoning
: food infection and food intoxication.
1)Food infection you eat microbes and
they grow in the gut and produce an
infection e.g Campylobacter jejuni,
Salmonella spp., Salmonella typhii,
Shigella spp., Vibrio cholerae, Vibrio
parahemolyticus, Vibrio vulnificus
2) Food intoxication you eat food
containing a toxin and that poison makes
you sick (Staphylococcus aureus )
including bacterially produced exotoxins,
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People at risk

Food poisoning is more likely to affect people with
lowered resistance to disease than healthy people
who might show mild symptoms or none at all.
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The following are particularly vulnerable to food
poisoning: - Elderly or sick people
- Babies
- Young children Pregnant women
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Factors affecting microbial growth in food
•
Time Moisture
Food Warmth
Intrinsic: conditions present in food
– Water availability (aw): amount of water in food
(pure water is 1.0)
• Most food >0.98; most bacteria require >0.90
– pH: most pathogens not grow at pH<4.5 (except
Lactic acid bacteria)
– Nutrients
• Extrinsic:
– Storage temperature
<0. 0C no growth (water crystallizes)
Refrigerator: 4⁰C to 10⁰C (enzyme rxns very slow
or non- existent
– Atmosphere: availability of O2
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In ideal conditions where there is
Moisture, Food and Warmth
(37degrees centigrade is ideal),
bacteria can double every 10 to 20
minutes. They do this by dividing in
to two. This is called
Binary Fission
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Spore
Spore forming inside cell
A resting resistant phase of some bacteria (including
Clostridium Perfringens and Botulinum and Bacillus
Cereus). The bacterium produces a protective coat
which helps it to survive high temperatures (up to
120°C) and lack of water. When favourable
conditions return, the spores split open and release
the bacteria which are then able to grow and multiply
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What Foods Are Most Likely to be
Contaminated?

raw meat and poultry

raw eggs (even in uncooked brownie, cake, or cookie
dough)
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unpasteurized milk
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raw shellfish
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unwashed raw fruits and vegetables

unpasteurized fruit juice
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Sources of microbial contamination of food

Food handler : bad personal hygiene, using same
cutting board for meat & vegetables, knife
contaminated by blood
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Food processing:
equipment ,packaging ,personal contamination
during processing
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Food storage: time & temp
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Fecal contamination in farms prior to collection
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Types of bacteria
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Spoilage: Not particularly harmful bacteria
which cause food to go off
Beneficial: “Good Bacteria” which are used
to make yoghurt and cheese
Pathogenic: Illness causing bacteria
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Symptoms of Microbiological
Food Poisoning
Infections require an incubation period of
generally 2 to 3 days. Typical symptoms:
 abdominal cramps
 diarrhea
 nausea, but…..there can be harsher
long-lasting effects.
Intoxications are often immediate,
(sometimes with 20 minutes) with nausea,
abdominal cramps and violent vomiting.
Illness is usually rather short-lived.
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Symptoms of
food poisoning
Nausea
Abdominal pain
Vomiting
Diarrhea
Gastroenteritis
Fever
Headache
Fatigue
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Causes of foodborne disease
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What Are the Most Common Causes of
foodborne Illness?
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Those caused by the bacteria:
• Campylobacter
• Salmonella
• E. coli O157:H7
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Those caused by a group of viruses:
• Norwalk and Norwalk-like viruses
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Causes of foodborne disease
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Infectious
Bacterial
Virus
Non-infectious
protozoae
Biological
Nonbiological
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Infectious causes of food poisoning
Bacteria
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Salmonella species
Campylobacter jejuni
Staphylococcus aureus
Clostridium perfringens
Clostridium botulinum
Bacillus and other sporing
bacilli
Shigella species.
E.coli
Yersinia enterocolitica
Vibrio parahaemolyticus,
Aeromonas hydrophilia,
Streptococcus
species
Group C, E and G .
The other e.g. Listeria
monocytogens
Viruses:
a-
Hepatitis A
b- Hepatitis E
c- Smal
lrounded
structured
viruses
(SRSV)
e.g.
Norovirus
Caliciviruse
s
Astroviruse
s
Rotaviruses
Protozoae
1- Giardiasis.
2- Amoebiasis
3 Cryptosporiosis
4- Isospora
5- Balantidum
6- Blastocytosis
hominis
7- Microsporidia
8- Toxoplasmosis
(?)
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Causes Of foodborne
Viruses
Unlike bacteria viruses do not multiply in Foods.
Acquired by:
a- Primary contamination
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From shell Fish
From Oysters
From Mussels
From Vegetables e.g Hepatitis A
From Vegetables irrigated by untreated water.
b- Secondary contamination.
 From Food handlers
e.g. Hepatitis A
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Non infective causes of food poisoning
 Non biological
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Physical
contamination:objects falling in
to food – metal,
glass, packaging
materials etc.
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 Biological
Chemical
contamination:Bleach, cleaning
chemicals getting
in to food ,heavy
metals
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Natural
contamination:
Poisonous plants
and berries,
undercooked red
kidney beans
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Causes of foodborne Diseases (Continued
Biological From:
a- Mushrooms
b- Harmful algal species
c- Fish e.g.
 Ciguatera Fish poisoning
 Scombroid Fish poisoning associated with
raised Histamine levels.
 Paralytic shell Fish poisoning
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Some Diseases Which Are Transmitted By
Food But Not Considered As Food
Poisoning:
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Bovine tuberculosis (milk)
Brucellosis (milk)
Toxoplasmosis (meat)
Listerosis (milk products)
Mad cow diseases virus etc.
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Exotoxins
• Produced inside bacteria and secreted
– Enterotoxin, Neurotoxin, Cardiotoxin
• Superantigen: Type I􀃆intense immune
response􀃆cytokines􀃆fever, nausea, vomitting,
shock (Staph aureus)
• Membrane disrupting toxin: Type II􀃆 lysis of
cells by disrupting membrane
• A-B toxins: Type III has two parts
– A is active enzyme toxin that inhibits protein
synthesis
and kills cell
– B binds to surface so toxin is transported across
plasma membrane (Clostridium
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Selected Clinical and Epidemiologic Characteristics of Typical Illness
Caused By Common foodbornee Pathogens*
Pathogen
Typical
Incubation
Period
Duration
Typical Clinical
Presentation
Assorted
Foods
Salmonella
species
1-3 Days
4-7 Days Gastroenteritis
Undercooked
eggs or
poultry,
produce
Campylobacter
jejuni
2-5 Days
2-10
Days
Undercooked
poultry,
unpasteurized
Bacterial
Gastroenteritis
dairy products
E. coli,
1-3 Days
Enterotoxigenic
3-7 Days Gastroenteritis
Many foods
Shigella species 1-2 Days
4-7 Days Gastroenteritis
Produce, egg
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salad
Listeria
monocytogenes
Variable
Gastroenteritis,
meningitis
abortion
Deli meat,
hotdogs,
unpasteurized
dairy products
Bacillus cereus 1-6 hour
<24 hour
Vomiting,
Gastroenteritis
Fried rice,
meats
Clostridium
botulinum
12-72 hour
Days-months
Blurred vision, Home-canned
paralysis
foods,
fermented fish
Staphylococcu
s aureus
1-6 hour
1-2 Days
Gastroenteritis,
particularly
nausea
Meats, potato
& pork,
unpasteurized
dairy
products.
Yersinia
enterocolitica
1-2 Days
1-3 weeks
Gastroenteritis,
appendicitislike syndrome
Undercooked
pork,
unpasteurized
dairy
products.
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2-6 weeks
Viral
Typical
Duration Typical
incubation
clinical
period
presentation
Norovirus
1-2 Days
Hepatitis A 15-50
virus
Days
Assorted
foods
12-60 Hr Gastroenteriti Under
s
cooked
shellfish
Weeksmonths
Hepatitis
Produce,
undercooked
shellfish
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Parasitic
Typical
incubation
Duration
Typical clinical
presentation
Assorted
foods
Cryptos
poridium
parvum
2-10 Days
Weeks
Gastroenteritis
Produce,
water
Cyclospora
cayetanesis
1-11 Days
Weeks
Gastroenteritis
Produce,
water
Toxoplasma
gondii
5-23 Days
Months
Influenza-like
illness,
Food
contaminated
by cat feces,
lymphadenopathy
undercooked
meat
Giardia
lamblia
1-4 Wk
Weeks
Gastroenteritis
Water
Taenia solium
Variable
Variable
Asymptomatic,
cysticercosis
Raw pork
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Important Microbial Causes of Food Poisoning
Toxin related
A. Staphylococcus aureus
24hourFlu?
:
incubation period < 6 hours
An intoxication Not infection
Clinical Features:
appear 1-6 hours after ingestion
and include vomiting (V), diarrhea
(D), and intense abdominal
pain/cramping (AB), usually no
fever
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-last approximately 24 hours
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Source: infected human & food
handlers
 Food contaminated -- enterotoxin
produced-toxin is heat stable
Diagnosis
1-epidemiological
2-isolating organism
from suspected food
3- toxin detection in
feacesof patient
Treatment
–none .
supportive
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S.aureus
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B- Bacillus cereus (from rice meals)
 Bacillus caereus is an spore forming aerobic
bacillus produces two types of enterotoxins.
a- Heat stable causing:
 emetic type of food poisoning
 incubation period < 6 hours
 vomiting, nausea
b- Heat labile causing:
 diarrheal type
 incubation period 6-24 hours
“BOTH TOXINS ARE PREFORMED IN FOOD”
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Clostridium Perfringens
 Causative agent: type A strains of C. perfringens (C.
Welchii)
 Gram positive anaerobic rod spore forming characterized
by sudden:
 Onset of colic
 Diarrhea
 Nausea
Pathogenesis
 Incubation period 10-16 hours
 Spore-vegetate in food, when swollen they sporulate in the
intestine and
 Produce toxin
Diagnosis:
 Detection of spores in food >105 spores
 Detection of spore in faeces >106 spores
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Botulism: Clostridium botulinum
•Gram positive anaerobic spore forming It produces a powerful
toxin The most lethal (killing toxin) 3 Kg can kill the whole
population of the world.
Foods associated: home canned “low acid” vegetables, honey
Pathogenesis Incubation period 12-24 hours under anaerobic
condition the spores germinate in the foods to produce the
toxin.
 Classified into A – G strains they produce the responsible
toxins A, B, E and F
 Toxin is heat labile
 Toxin inhibits release of acetylcholine at neurone muscular
junction leading to flaccid paralysis.
Symptoms:12-72 hours after ingestion
neurological blurred vision, and
descending muscle weakness-flaccid paralysis
• Treatment: antitoxin not antibiotics
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Campylobacter jejuni
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General characteristics: gram negative curved rod,
microaerophile, one or two polar flagella, no capsule
Special culture to grow:, 42⁰C incubator
Source Part of the normal flora of poultry and dairy cattle
- unpasteurized milk,
-undercooked poultry (shwarma)- may be found at a
concentration of 109cells/gram of chicken
 Incubation period: 2-5 days
• Symptoms: Person to person
D (which may be bloody), AB,fever (1040C),
vomiting uncommon
– Last 2-10 days
– Some cases lead to Guillen-Barre syndrome
and Rheumatoid Arthritis weeks
 Diagnosis : Gram stain of feaces shows spiral organisms
 Treatment: none, mostly supportive care
-some cases require antibiotics
(erythromycin, quinolones)
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Listeriosis

Causative agent Listeria monocytogenes
 Gram positive rod aerobic . Resembles dipththeroids
 Can multiply at lower temperature 4°C
Sources Wide spread in dust, soil, water, sewage, vegetation,
animals feeds, poultry, hot dogs,meat, fish, vegetable
Diseases - Infects GI tract (usually few symptoms),penetrates
mucosa & enters blood stream
- Fourth leading cause of meningitis (perhaps 50% fatality )
-Pregnant women: crosses placenta and causes, febrile
illness abscess in fetal tissue 􀃆miscarriage or stillbirth (60 %)
- Neonates – meningitis
- Immunocompromised patients – febrile illness
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Salmonella
General characteristics: gram negative rod, facultative anaerobe,
peritrichous flagella
 Caused by No typhoid causing Salmonellas.
(Called Food poisoning gastro intestinal Salmonellas.)
 Causes about 85% of cases of Food poisoning or Food borne
diseases (Shawrma)
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Sources
• Raw poultry and eggs
• Raw milk
• Raw beef
• Unwashed fruit, alfalfa sprouts
• Reptile pets: Snakes, turtles, lizards
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Part of the normal flora of poultry, reptiles
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Most Salmonella killed by acid so need to ingest large numbers
to survive stomach acid in order to cause infection
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Salmonella
Culture: isolate and identify lactose negative & H2S
positive
Incubation time: 12-36 hours
Symptoms: include D, AB, and a moderate fever
Full recovery in a few days but may shed the organism for
6 mnths
Approx. 2-4 million cases/year, only 40-50,000 are actually
reported
Salmonella typhimurium and enteritidis:
– Most common serovars in USA
– Antibiotics not advised due to increasing
resistance (due to widespread addition of
antibiotics to animal feed)
– Do Not treat gastroenteritis unless invades tissues
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Shigella
General characteristics: gram negativerod facultative
anaerobe, lactose negative
• Only found in the feces of other humans
• Organisms transmitted by the five F’s
-food, fingers, feces, flies, and fomites
Shigellosis or bacillary dysentery
Incubation time: 24-48 hours
– Only need 10 cells to cause infection; not
affected by stomach acid
• Symptoms: F, AB, D (may contain blood and mucus)
• See passage of small volume bloodystools (20/day)
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Shigella
• S. sonnei-most common species in US,
responsible; relatively mild; may cause
some of traveler’s diarrhea
• S. dysenteriae-causes more serious
infection dysentery
-due to the production of a Shiga toxin
(A-B toxin)
-in tropical areas-death rate up to 20%
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Dysentery
• Shigella dysenteriae
– Virulent strains have plasmids to attach to epi cells of
intestine; membrane ruffles around and engulfs
bacteria which multiply in cell and produce
Shiga toxin which destroys tissue; also has
mechanism that allows to spread from cell to cell;
sloughed areas of epis leads to intenseinflammation,
pus, and bleeding
– Rarely invades blood
– Toxin strongly associated with hemolytic uremic
syndrone; RBCs break in tiny blood vessels leading
to anemia and kidney damage
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Salmonella
Shigella
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Cholera
Curved gram negative rod, facultative anaerobe
single polar flagella
• Can exist in saltwater for extended periods of time;
tolerates high pH and high salt concentrations
• Killed by stomach acid so need large numbers of
organisms to cause infection
Incubation time: several hours to days
• Symptoms: “rice water stools”, suddenonset of
explosive watery diarrhea (up to20 liters/day) with
vomiting and pain
• Cholera toxin is the key pathogenic feature
– A-B toxin causes activation on enzyme that causes cells
to continuously secrete chlorideions and electrolytes
and H2O􀃆 watery diarrhea
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Non-cholera Vibrios
• V. parahemolyticus: halophilic (requires sodium);
Inhabits coastal salt waters; usually transmitted
by raw or undercooked shellfish; less severe
gastroenteritis
• V. vulnificus: halophilic (requires 1% NaCl);
wound infections—minor skin infection in coastal
water􀃆rapid sread through tissues􀃆possible
amputation
– Fatal specticemia in 50% of patients with liver
disease
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Escherichia coli
•
Normal bowel flora
• Strains that cause GI disease have virulence factors
(coded by plasmids)
– Enterotoxin production
– Abiltiy to adhere to small intestin
Diarrhea causing E. coli:
Classified according to virulence
– Entertoxigenic E. coli (ETEC)
– Enterpathogenic E. coli (EPEC)
– Enterohemorrhagic E. coli (EHEC)
– Enteroinvasive E. coli (EIEC)
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Entertoxigenic E. coli (ETEC)Enterpathogenic E. coli
(EPEC)
• Also known as traveler’s
diarrhea
• Attacks the small intestine
•Two Enterotoxins promote • In developing countries
the pumping of Cl- and
accounts for 20%of
inhibition of NaCl which
diarrhea in bottle-fed
results in diarrhea
infants
– Profuse watery stools
• Attaches to mucosa of small
intestine and causes cell
• No invasion
surface changes
• Can develop immunity
(loss of microvilli)
• Prevent with bismuth
(Pepto-Bismol)
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Enteroinvasive E .Coli
(EIEC)
• Invades lining Of
large intestine causing
necrosis, inflammation,
and ulceration of large
bowel
Enterohemorrhagic E. coli
(EHEC)
• Obtain from the consumption
of animal products
• Small dose (< 100 bacteria) to
infect
• Attacks the colon
Shiga like toxin and
• Usually seen in children • Produces
lesion; inflammation and
inn areas with poor
bleeding (hemorrhagic
sanitation
colitis)
• O157:H7 causes bloody
diarrhea which may lead to
hemolytic uremic syndrome
• Sorbitol negative MacConkeys
used to isolate;
culture all bloody diarrhea
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Yersinia enterocolitica
• Gram negative rod; lactose negative; grows at 4⁰C
• Inhabits domestic animals (contaminates meat and
milk)
• Fever, diarrhea, abdominal pain
• Can invade mucosa and spread to
lymphatics (may present as appendicitis)
•
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Food Poisoning Outbreaks:
1.Illness in a period of time - few hours, few weeks.
2.In individuals who consumed common food.
3.Many acute cases can happen
4.Proper evaluation of cases and implicated food is
essential
5.Single cases are difficult to recognized unless
they have a distinctive clinical syndrome e.g.
Botulism
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LABORATORY DIAGNOSIS OF
FOOD POISONING OUTBREAKS
1- Type of Food
2-Incubation period
3-Isolation of the causative
agent from
a- Patient faeces, Vomit
b- From incriminated food
and related articles.
4- Investigation of Food
Handlers in the same way.
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LABORATORY INVESTIGATIONS OF
FOOD HANDLERS
1-Most Important to explain the procedure
2-Don’t frightened the food handlers
3-Look for Salmonellae, Giardia, Amebae
4-Stop work until three specimens are negative
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Is it safe to eat?
‘Use by’ dates are
used for perishable
foods,
e.g. cheese, milk
‘Best before’ dates are used for
less perishable foods, e.g. canned
baked beans, jar of jam and frozen
fish fingers.
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Where should these foods be
stored?
Different foods are stored in a variety of
ways to keep them safe to eat for longer.
Dry cupboard
Refrigerator
Freezer
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© British Nutrition Foundation 2003
Raw and cooked foods
Raw meat and poultry
should be stored on the
bottom shelf of the fridge
to prevent crosscontamination.
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© British Nutrition Foundation 2003
Fruit and vegetables
Always wash fruit and vegetables
before you eat or use them to cook.
This removes dirt and other
and other particles.
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© British Nutrition Foundation 2003
Prevention
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Cook: Cook to Proper Temperatures use a food thermometer to check
ttemperature of food that you cook
Chill: Refrigerate Promptly keepcoldfoods cold! Divide large
amounts of food for quick cooling
in the refrig
Clean: Wash Hands and Surfaces Often
- plain soap and plenty of water,
scrubbing for 20 seconds
Separate: Prevent Cross
Contamination – keep raw and readyto-eat foods away from raw meat
Store: Store Foods Properly – check
package labels for use-by dates

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THANK YOU
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