Biomedical Engineering Reference
In-Depth Information
honey have been known to produce active Clostridium botulinum infection in
children.
Clostridium difficile inhabits human intestine and is non-pathogenic under
normal circumstances. After long-term antibiotic use, when many of the nor-
mal gut bacteria are reduced in number, an overgrowth of Clostridium diffi-
cile may cause severe gastrointestinal disease (so-called pseudomembranous
colitis). Colon ulcerations, with an overlying pseudomembrane composed of
necrotic mucosal cells admixed with inflammatory cells,
is the hallmark
of this disease.
Clostridium perfringens is a ubiquitous organism that is sometimes
found in the human gastrointestinal tract, without causing disease. It is a
common cause of food poisoning. When contaminated food is ingested,
diarrhea often follows, in about 10 hours, in susceptible individuals (some
individuals are resistant to enteric disease). Clostridium perfringens is a
common infection in necrotic tissue, due to the anoxic conditions therein.
The organism causes so-called gas gangrene (tissue necrosis accompanied
by the liberation of bacterial-produced gas). Clostridium perfringens also
causes emphysematous gangrenous cholecystitis, a condition occurring
with gallbladder necrosis, in which the necrotic gallbladder tissue is infil-
trated by gas, produced by the organism. The ability of Clostridium perfrin-
gens to produce gas has a beneficial purpose: as a leavening agent for
baked goods.
Clostridium tetani is the cause of tetanus. Spores live in soil, and human
infection usually follows the mechanical introduction of soil-borne spores
into a wound. The organism produces a potent neurotoxin that manifests
clinically as muscle rigidity: risus sardonicus (rigid smile), trismus (also
known as lock-jaw, rigid jaw), and opisthotonus (rigid, arched back).
Though only members of Class Bacilli and Class Clostridia have the
ability to form endospores, not all members of these two classes are spore-
forming. Genus Peptostreptococcus is the exception. Species of genus
Peptostreptococcus are found as commensals in virtually every type of mucosa
that lines humans. They have pathogenic potential when they are traumatically
introduced deep into tissues, or when the host becomes weakened from
concurrent chronic infections, or when the host becomes immune-deficient.
Under these circumstances, they can produce sepsis, with abscesses occurring
in multiple organs.
Clostridia
Veillonellaceae
*Veillonella
Species in Genus Veillonella are normal inhabitants of the GI tract of
humans and other mammals. As with infections from Peptostreptococcus
species, Veillonella species may cause sepsis, with multi-organ disease in
predisposed individuals. Veillonella infections are rare.
