Biomedical Engineering Reference
In-Depth Information
species can infect healthy persons, most
infections arise in immune-
compromised patients and in children.
Several of the diseases produced by members of Genus Bartonella
are pathologically unique: Carrion's disease, cat-scratch fever, peliosis, and
bacillary angiomatosis.
Carrion's disease, caused by Bartonella bacilliformis, is endemic in Peru
and only occurs in South and Central America. It produces an acute phase
characterized by fever, hepatomegaly, splenomegaly, lymphadenopathy, and
hemolysis (see Glossary item, Hemolytic syndromes). A chronic phase, known
as Verruga Peruana (Peruvian wart) presents as a skin rash characterized
histologically by marked proliferation of endothelial cells.
Cat-scratch disease is caused by Bartonella henselae, and possibly
Bartonella clarridgeiae, and has a cat reservoir. The mode of infection is some-
what controversial. Despite the name given to the disease, implying a scratch
inoculation, it is likely that fleas carry the bacteria from cats to humans. The
disease produces a localized, somewhat persistent, lymphadenopathy, often
accompanied by systemic complaints.
Immune-compromised individuals, especially AIDS patients, may form
an exaggerated endothelial growth reaction in the skin (bacillary angiomato-
sis) and in the liver (peliosis hepatis, characterized by localized areas of vas-
cular dilatation and blood pooling). In the skin, the lesions mimic Kaposi's
sarcoma (Human herpesvirus 8, in Group I Viruses, Chapter 39), also seen in
immune-compromised individuals. In the case of bacillary angiomatosis,
Bartonella organisms can be histologically identified in the proliferating
endothelial cells. Bacillary angiomatosis can be caused by Bartonella hense-
lae, the same organism that causes cat-scratch fever, transmitted by cat
scratch, cat bite, and possibly ticks and fleas. Bacillary angiomatosis is also
caused by Bartonella quintana, transmitted by lice.
Various species of Bartonella have recently been associated with bacter-
emias with or without endocarditis, myocarditis, and retinitis. It is likely that
additional pathogenic Bartonella species will be identified, as the techniques
for analyzing blood samples continue to improve.
Readers should be careful not to confuse Bartonella with the similar-
sounding Bordetella (Beta Proteobacteria, Chapter 6).
Genus Brucella contains facultative intracellular organisms transmitted from an
animal reservoir, usually via drinking unsterilized milk, or through direct contact
with animals or their secretions. Human-to-human transmission may occur, rarely.
Infection is usually accompanied by fever, arthralgia, myalgia, and bacteremia.
Brucella species causing brucellosis include: Brucella abortus (cattle reservoir),
Brucella canis (dog reservoir, rare in humans), Brucella melitensis (sheep and
cattle reservoir), and Brucella suis (pig reservoir, occurring in human handlers).
Because Brucella is a facultative intracellular pathogen, it can live for
some time outside of host cells; hence its mode of transmission, via milk and
secretions. The ability to survive outside of host cells is unusual among
