TABLE 53.1 Chemotherapeutic Agents Used in Treatment of Protozoal Disease
Mode of Action
Arsenicals (melarsoprol, tryparsamide), antimonials Paromomycin
Diloxanide furoate Eflornithine
Binds with SH groups;selectively inhibits pyruvate kinase or phosphofructokinase Interferes with initiation complex;
causes misreading of mRNA Binds to kinetoplast DNA
Inhibits DNA replication
Generation of toxic oxygen radicals Binds to plasma proteins;
inhibits glucose utilization Steadily liberates inorganic iodine in the lumen Unknown
Inhibits ornithine decarboxylase and biosynthesis of polyamines
Affects cellular structure, function, synthesis or energy production
Affects protein structure, function, synthesis
Affects synthesis or structure of nucleic acids Affects synthesis or structure of nucleic acids Unknown Unknown
Affects cell division, differentiation
SH, sulfhydryl;mRNA, messenger RNA
Trophozoites may spread to the liver through the portal vein and produce acute amebic hepatitis, or more rarely, the trophozoites may encyst and produce an amebic liver abscess many years later. On rare occasions, amebic abscesses are found in other organs, such as the lungs or the brain.
Many patients continue to excrete cysts for several years after recovery from the acute disease and therefore are a hazard to themselves and other persons; the public health risk is greatest when persons employed as food handlers are affected. More recently, it has been recognized that infection can be transmitted by sexual activities.
Balantidium coli is the largest of the protozoans that infect humans. The trophozoite form is covered with cilia, which impart mobility. Infection is acquired through the ingestion of cyst-contaminated soil, food, or water. The trophozoite causes superficial necrosis or deep ulceration in the mucosa and submucosa of the large intestine. Otherwise healthy persons commonly exhibit nausea, vomiting, abdominal pain, and diarrhea, whereas debilitated or nutritionally stressed patients may develop severe dysentery.
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