Page 800 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

VetBooks.ir Chapter 56

Enterotoxins

Larry J. Thompson

INTRODUCTION (and other animals) are not susceptible to food poisoning
and thus may feed their pets foods that humans would
The term food poisoning can be used to describe the
rather not ingest. Discarded foodstuffs are often high in
result of eating pathogenic organisms or toxins in contam-
proteins and carbohydrates and serve as excellent sub-
inated food. The list of causative agents for food-borne
strates for the rapid growth of bacteria, often with entero-
illness can be quite lengthy, including infectious agents
toxin release. Instances of garbage intoxication increase
(e.g., bacteria, viruses, and parasites); natural toxins (e.g.,
during warm weather and during major holidays when
bacterial toxins, mycotoxins, shellfish poisons, and plant
increased food is prepared and discarded. Under condi-
poisons); and other contaminants (Mead et al., 1999).
tions of warm temperatures and adequate moisture, these
Veterinarians and owners often use the term garbage
discarded foodstuffs can have an almost explosive growth
intoxication or garbage poisoning to describe the situation
of bacteria, especially S. aureus and B. cereus, which are
in which animals, especially dogs, eat discarded or other-
the most common causes of enterotoxin-related food
wise poorly preserved foodstuffs and subsequently
poisonings in humans. Although a great deal of time and
develop a syndrome composed mainly of severe vomiting
energy has been expended by public health officials in the
and diarrhea. This chapter is focused on the effects of
pursuit of the origin and control of food poisonings in
enterotoxins, which are defined as those bacterial exotox-
humans, there is a paucity of specific information
ins that are specific for the intestinal tract causing vomit-
concerning animals.
ing, diarrhea, and abdominal pain. Although many
organisms produce enterotoxins (Vaishnavi, 1996;
Fasano, 2002), those produced by Staphylococcus aureus
and Bacillus cereus are stressed in this chapter. In con- PHARMACOKINETICS AND MECHANISM
trast to enterotoxin, the term endotoxin is used to describe OF ACTION
a cell-associated bacterial toxin, usually a lipopolysaccha-
S. aureus is a facultative anaerobic Gram-positive coccus
ride complex that is found on the outer membrane of
that may be single, paired, or in a grape-like cluster.
Gram-negative bacteria. Endotoxins essentially remain
S. aureus does not form spores and thus contamination
associated with the cell wall until the destruction of the
may be avoided by proper heat treatment of food to kill
bacteria by autolysis, external lysis, or phagocytic diges-
the bacteria. S. aureus is able to grow in a wide range of
tion. Although all animals can be affected by endotoxin,
temperatures (7 48.5 C), with an optimum range from

horses are especially prone to disease complications due
30 Cto 37 C. S. aureus can also grow over a wide pH

to endotoxemia (Werners et al., 2005).
range (4.2 9.3) and can tolerate sodium chloride concen-
trations of up to 15%. These characteristics allow it to
grow in a wide variety of foodstuffs and in situations of
BACKGROUND
discarded food. S. aureus is also an important infective
This chapter focuses on the most common situations asso- pathogen and can easily be found in the nostrils and on
ciated with enterotoxin exposures in veterinary medicine, the skin of most mammals (Le Loir et al., 2003). A high
namely dogs ingesting garbage, carrion, or other spoiled prevalence of enterotoxigenic S. aureus was reported for
foodstuffs. Dogs readily consume a wide variety of such pet dogs and cats, with the highest incidence of positives
material, and owners often are unaware when their animal (10%) being isolated from the mouths of dogs (Abdel-
has had access to or has consumed foodstuffs of doubtful moein and Samir, 2011). At least 14 different
origin. Many owners have the mistaken opinion that dogs Staphylococcal enterotoxin (SE) types have been found,
Veterinary Toxicology. DOI: http://dx.doi.org/10.1016/B978-0-12-811410-0.00056-8
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