Biomedical Engineering Reference
In-Depth Information
produces a toxin that causes enteritis when ingested in food that has been
colonized by the bacteria.
Staphylococcus epidermidis is a commensal that lives on human skin. It is
non-pathogenic in most circumstances. Chronically ill patients with indwelling
catheters are prone to urinary tract infections caused by Staphylococcus
epidermidis. This organism can grow as a biofilm, enhancing its ability to glide
over surfaces (such as catheters). Nosocomial opportunistic organisms, that
glide into tissues via an invasive instrumented portal (e.g., catheter, intraven-
ous line, pulmonary assistance tubing) were described earlier with Class
Pseudomonadales (Class Gamma Proteobacteria, Chapter 7) and again with
the gliding bacteria (Class Bacteroidetes and Class Fusobacteria, Chapter 10).
Bacilli
Bacillales (catalase positive)
Bacillaceae
*Bacillus
Bacillus cereus causes food-borne enteritis. Bacillus cereus endospores can
survive conditions that would kill other bacterial forms. Consequently, food
poisoning due to Bacillus cereus occurs under similar conditions as food poi-
soning due to Clostridium perfringens (see below) or Staphylococcus aureus
(see above). Depending on the strain of Bacillus cereus and the conditions
of its growth, an enterotoxin may accumulate in contaminated food. If pre-
formed enterotoxin is present in contaminated food, emesis often results,
within a few hours, and the condition may simulate Staphylococcus aureus
food poisoning (see above). If no enterotoxin is present in food contaminated
with Bacillus cereus, diarrhea usually begins after about 10 hours, and the
condition may simulate infections with Clostridium perfringens.
Bacillus anthracis is the cause of anthrax, an acute disease that is often
fatal if not treated quickly and aggressively. The disease is transmitted by
endospores (not by active bacteria) that are, in most cases, spread by infected
animals. Animals become infected by grazing on plants and soil containing
long-dormant spores, or by eating an actively infected animal. Humans
become infected by inhaling endospores emanating from the carcass of a
dead infected animal (leading to pulmonary anthrax), by eating undercooked
infected animals (leading to enteric anthrax), or by handling infected ani-
mals, with spores entering the skin through abrasions (leading to cutaneous
anthrax). Anthrax has been weaponized by various governments over the
decades, but its long dormancy and the difficulty containing spores within a
specified target location, have made this weapon a double-edged sword [55].
Bacilli
Lactobacillales (catalase negative)
Enterococcaceae
*Enterococcus
