Biomedical Engineering Reference
In-Depth Information
are cell-wall lipopolysaccharides. These molecules can produce generalized inflamma-
tory reactions when injected into humans (e.g. fever, drop in blood pressure, activation
of the inflammation and blood cascades). Endotoxins are typically found on the outer
membrane of the cell wall. Gram-negative bacteria have an outer membrane that
impedes the entrance of the Gram stain. Gram-positive bacteria lack this outer mem-
brane and provide easy access to the Gram stain. It is not surprising, therefore, that
most endotoxins come from Gram-negative bacteria. A classic example of an endo-
toxin is found in meningococcemia, due to infection with Neisseria meningitidis (Beta
Proteobacteria, Chapter 6).
Exotic diseases in the United States For many, the word “exotic” brings to mind all
things strange and exciting. For clinical microbiologists, “exotic” refers to infectious
diseases that have arrived via a distant geographic location. In the United States, a
variety of exotic diseases have been introduced in the past few decades due, primar-
ily, to two influences: global warming and global travel. The normal habitat of many
disease vectors is a tropical climate. As the temperature of the planet rises, the geo-
graphic range for tropical vectors expands. As for travel, one of the most devastating
disease vectors is the jet airplane. Jets transport infectious passengers and vectors.
Can it be just a coincidence that the major corporations of the airline industry are
called “carriers”? Here are a few of the exotic diseases that have been introduced or
re-introduced into the USA, in the past few decades: West Nile fever, yellow fever,
Mayaro fever, Dengue fever, Chikungunya, SARS, monkeypox, CJD/BSE, HIV/
AIDS, Lassa fever, malaria, leishmaniasis, Chagas disease, cyclosporan gastroenteri-
tis, cholera [76].
Facultative intracellular organism An organism that is capable of living, and reprodu-
cing inside or outside of cells. The term may apply to any organism, but most of the
facultative intracellular organisms are bacteria. Example genera include: Brucella,
Francisella, Histoplasma, Listeria, Legionella, Mycobacterium, Neisseria,
and
Yersinia. See Obligate intracellular organism.
HACEK A group of proteobacteria, found in otherwise healthy individuals, that are
known to cause some cases of endocarditis, especially in children, and which do not
grow well from cultured blood (due primarily to their slow growth rates). The term
HACEK is created from the initials of the organisms of the group:
Haemophilus,
particularly Haemophilus
parainfluenzae Gamma Proteobacteria
(Gamma Proteobacteria, Chapter 7)
Aggregatibacter,
including
Aggregatibacter
actinomycetemcomitans
and
Aggregatibacter aphrophilus (Gamma Proteobacteria, Chapter 7)
Cardiobacterium hominis (Gamma Proteobacteria, Chapter 7)
Eikenella corrodens (Beta Proteobacteria, Chapter 6)
Kingella, particularly Kingella kingae (Beta Proteobacteria, Chapter 6)
Hemolytic syndromes Hemolytic syndromes are characterized by the destruction of red
blood cells. Red cell destruction is caused by organisms that invade and rupture the
cells (e.g. Plasmodium species, Babesia species), or that release chemicals that lyse
red cells (e.g. hemolysins, listeriolysin O, rhamnolipid), or that induce an antigenic
response against the patient's own red cells (post-streptococcal autoimmune hemolytic
anemia). Hemolytic syndromes
(red cell
lysis)
should be distinguished from
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