Agriculture Reference
In-Depth Information
Table 12.1
Bacterial causes of food-borne infection
Agent
Normal
incubation period
Normal duration
Main clinical symptoms
Commonly associated foods
B. cereus emetic toxin
1-5 hours
<24 hours
Vomiting
Cereals, rice
B. cereus enterotoxin
8-16 hours
<24 hours
Abdominal pain, diarrhoea
Cereals, rice
Campylobacter spp.
3-5 days
2-7 days
Abdominal pain, diarrhoea
(sometimes bloody), headache,
fever
Poultry, cooked meats, milk
Cl. botulinum
12-36 hours
Extended
Swallowing difficulties, perhaps
as respiratory failure
Preserved foods,
e.g., canned, bottled
Cl. perfringens
10-12 hours
24 hours
Abdominal pain, diarrhoea
Stews, roasts
E. coli 0157
12 hours-10 days
Possibly extended
Abdominal pain, diarrhoea
(may be bloody). May lead to
renal failure
Beefburgers, meat, dairy
products
L. monocytogenes
3-21+ days
Varies
Fever, headache, spontaneous
abortion, meningitis
Soft cheeses, patés, poultry
meat
Salmonella spp.
12-36 hours
2-20 days
Abdominal pain, diarrhoea,
fever, nausea
Meat, poultry, eggs, dairy
products
Staph. aureus
2-6 hours
12-24 hours
Vomiting, abdominal pain,
diarrhoea
Cooked meat, human source
V. parahaemolyticus
12-24 hours
1-7 days
Abdominal pain, watery
diarrhoea, headache, vomiting
fever
Shellfish
Y. enterocolitica
3-7 days
1-3 weeks
Acute diarrhoea, abdominal
pain, fever and vomiting
Pig meat products
not at all below 30°C. They are most unlikely to multiply
on food at room temperature. They are not heat resistant
and can be killed by cooking. As though to compensate
for their inability to grow on food, they have an extremely
low infective dose, with as few as 500 cells being suffi-
cient to cause human infection.
Campylobacter
spp.
Campylobacters, although long recognised by veterinar-
ians as a cause of animal disease, were not associated
with human enteric infection until 1975. Since then, the
number of isolates in the United Kingdom and across the
EU has steadily increased until they have become the
most numerous cause of human bacterial enteric infec-
tion. Undoubtedly, improved laboratory methods have
contributed to this rise, although, in addition, a true
increase has occurred.
The traditional animal strains of
Campylobacter fetus
fetus
and
C. fetus venerealis
rarely cause human infection
and the most common types in the EU are
C. jejuni
,
C. coli
and
C. lari.
Serological sub-typing is not as well
developed as that for salmonella, and most isolates are
not further sub-typed. This makes epidemiological
investigation very difficult as it is not easy to confirm the
origin of human infection. A baseline study carried out
within the EU in 2008 estimated that 70% of batches of
broilers presented for slaughter were colonised.
Unlike many other food-borne organisms,
Campylo-
bacter
spp. are fastidious in their growth requirements.
They are Gram-negative and microaerophilic, requiring
a low oxygen concentration (5%). They are slender,
curved and highly mobile and grow best at 42-43°C and
Infection in humans
With a reported incidence in
humans of 44 confirmed cases per 100,000 of the human
population, there is an estimated 9 million cases of
human illness per annum within the EU.
The normal incubation period is 3-5 days, but some
evidence exists that this can be considerably extended.
A characteristic of infection is acute abdominal pain,
which can be so severe as to be mistaken for appendicitis,
sometimes precipitating unnecessary surgery. This pain
is often accompanied by bloody diarrhoea and fever,
but vomiting is rare. Most infections resolve spontane-
ously within one week, while others can be prolonged.
Complications during the acute phase are unusual and
only exceptionally does death occur. There is, however,
increasing evidence that there may be longer-term
sequelae to campylobacter infection including both
reactive arthritis and even peripheral polyneuropathy
(Guillain-Barré syndrome).
