Amebicides are drugs toxic to amoebas such as Entamoeba Entamoeba A genus of ameboid protozoa characterized by the presence of beaded chromatin on the inner surface of the nuclear membrane. Its organisms are parasitic in invertebrates and vertebrates, including humans. Nitroimidazoles histolytica (the causative organism of amebiasis Amebiasis Amebiasis, or amoebic dysentery, is an infection caused by the parasite Entamoeba histolytica. Transmission is through the fecal-oral route or by consumption of contaminated food and water. Most patients infected with E. histolytica are asymptomatic, but about 10% may develop dysentery. Entamoeba spp./Amebiasis). Parasites enter the GI tract where trophozoites can penetrate the intestinal wall and cause an invasive infection. Amebicides are classified based on where the drug is most effective: intestinal lumen or tissues. Intestinal-lumen amebicides include iodoquinol and paromomycin. Tissue amebicides include the nitroimidazole drug class (e.g., metronidazole Metronidazole A nitroimidazole used to treat amebiasis; vaginitis; trichomonas infections; giardiasis; anaerobic bacteria; and treponemal infections. Pyogenic Liver Abscess, tinidazole Tinidazole A nitroimidazole alkylating agent that is used as an antitrichomonal agent against trichomonas vaginalis; entamoeba histolytica; and giardia lamblia infections. It also acts as an antibacterial agent for the treatment of bacterial vaginosis and anaerobic bacterial infections. Nitroimidazoles). Treatment of symptomatic disease usually requires a combination of both classes.
Last updated: 16 Sep, 2021
The pathogenesis of invasive
Entamoeba
Entamoeba
A genus of ameboid protozoa characterized by the presence of beaded chromatin on the inner surface of the nuclear membrane. Its organisms are parasitic in invertebrates and vertebrates, including humans.
Nitroimidazoles histolytica infection:
In 10% of cases, E. histolytica colonizes the
large intestine
Large intestine
The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal.
Colon, Cecum, and Appendix: Anatomy mucosa and invades via
secretion
Secretion
Coagulation Studies of proteinases and lytic
enzymes
Enzymes
Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules.
Basics of Enzymes. This causes cellular
necrosis
Necrosis
The death of cells in an organ or tissue due to disease, injury or failure of the blood supply.
Ischemic Cell Damage and lysis of the membranes, respectively. This chain of events induces mucosal cell
apoptosis
Apoptosis
A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, I.e., DNA fragmentation. It is genetically-programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.
Ischemic Cell Damage and disrupts
tight junctions
Tight junctions
Cell-cell junctions that seal adjacent epithelial cells together, preventing the passage of most dissolved molecules from one side of the epithelial sheet to the other.
The Cell: Cell Junctions between cells, allowing for
flask-shaped ulcers
Flask-Shaped Ulcers
Entamoeba spp./Amebiasis, abscesses, and fistulas to form. Invasion may reach the portal venous system, through which E. histolytica can spread to other organs.
A combination of tissue and luminal amebicides are prescribed to treat amebiasis Amebiasis Amebiasis, or amoebic dysentery, is an infection caused by the parasite Entamoeba histolytica. Transmission is through the fecal-oral route or by consumption of contaminated food and water. Most patients infected with E. histolytica are asymptomatic, but about 10% may develop dysentery. Entamoeba spp./Amebiasis.
Luminal amebicides:
Tissue amebicides:
Iodoquinol is used to treat amebiasis Amebiasis Amebiasis, or amoebic dysentery, is an infection caused by the parasite Entamoeba histolytica. Transmission is through the fecal-oral route or by consumption of contaminated food and water. Most patients infected with E. histolytica are asymptomatic, but about 10% may develop dysentery. Entamoeba spp./Amebiasis (limited availability in the United States):
Iodoquinol is contraindicated in individuals with an allergy Allergy An abnormal adaptive immune response that may or may not involve antigen-specific IgE Type I Hypersensitivity Reaction or intolerance to iodine Iodine A nonmetallic element of the halogen group that is represented by the atomic symbol I, atomic number 53, and atomic weight of 126. 90. It is a nutritionally essential element, especially important in thyroid hormone synthesis. In solution, it has anti-infective properties and is used topically. Thyroid Hormones.
The site of action for
aminoglycosides
Aminoglycosides
Aminoglycosides are a class of antibiotics including gentamicin, tobramycin, amikacin, neomycin, plazomicin, and streptomycin. The class binds the 30S ribosomal subunit to inhibit bacterial protein synthesis. Unlike other medications with a similar mechanism of action, aminoglycosides are bactericidal.
Aminoglycosides, which target the 30S ribosomal subunit
tRNA
tRNA
The small RNA molecules, 73-80 nucleotides long, that function during translation (translation, genetic) to align amino acids at the ribosomes in a sequence determined by the mRNA (RNA, messenger). There are about 30 different transfer rnas. Each recognizes a specific codon set on the mRNA through its own anticodon and as aminoacyl trnas (RNA, transfer, amino Acyl), each carries a specific amino acid to the ribosome to add to the elongating peptide chains.
RNA Types and Structure: transfer
RNA
RNA
A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity.
RNA Types and Structure
mRNA
mRNA
RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3′ end, referred to as the poly(a) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.
RNA Types and Structure: messenger
RNA
RNA
A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity.
RNA Types and Structure
Caution should be used in individuals with:
In addition to anaerobic bacterial infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, nitroimidazoles Nitroimidazoles Nitroimidazoles are prodrugs composed of an imidazole ring with an attached nitro group. Nitroimidazoles are reduced within susceptible microorganisms, leading to free radical formation and disruption of DNA integrity. Nitroimidazoles can be used for: