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Giardia lamblia
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
Infrequently, syndromes related to the biliary system may accompany giardiasis. These syndromes include nonopacification of the gall bladder on oral cholescystography (162) and cholecystitis (163). The presence of trophozoites in the gall bladder and biliary passages, which was reported over 50 years ago (164), may contribute to these conditions. Russian and Polish clinicians also have reported cholecystitis (165-167) as well as pancreatitis (168) in association with giardiasis. A case of granulomatous heptatitis has been attributed to infection with G. lamblia (169). The mechanism for the association of these biliary tract, pancreatic, and hepatic conditions with giardiasis may involve trophozoites ascending the common bile duct and then inducing an inflammatory reaction in the end organs. In contrast, the identification of G. lamblia trophozoites in the hepatic vessels of rodents (170) suggests that the parasite also could gain access to the liver via the portal venous system after penetrating the intestinal mucosa. However, this route of access to the liver seems exceedingly unlikely, since in humans trophozoites do not enter the vascular system.
Pathobiology of Amebiasis
Published in Roberto R. Kretschmer, Amebiasis: Infection and Disease by Entamoeba histolytica, 2020
Ruy Pérez-Tamayo, Ingeborg Becker, Irmgard Montfort, Ruy Pérez-Montfort
Despite the fact that Entamoeba histolytica has been known to be the cause of human amebiasis for more than 100 years, and that current estimates of the disease reveal a prevalence of 400 × 106 cases per year (approximately 10% of the world population1) there is still much that is not adequately understood in this peculiar host/parasite relation. The life cycle of the parasite lacks sexual stages and intermediate hosts, and oscillates between two different forms, the infective cyst and the vegetative trophozoite, but the conditions required for both encystation and excystation are not known. This has proven a formidable stumbling block for the experimental reproduction of the disease, which has yet to be satisfactorily accomplished. The trophozoite reproduces by binary fission, but the organization of its nuclear DNA during reproduction, and even the existence of chromasomes, are still undecided. The life cycle of E. histolytica does not require a tissue invasive and destructive stage, since the parasite can survive and reproduce in the lumen of the intestine, undergo encystment and pass with the stools to the outer world. But in some cases the trophozoites destroy the intestinal mucosa and invade the intestinal wall, causing what is known as invasive intestinal amebiasis. Again, virtually nothing is known about the conditions that permit or inhibit such aggressive behavior of the parasite. In fact, there is still controversy over the real existence of permanently nonpathogenic and pathogenic strains of E. histolytica.
Tropical Colorectal Surgery
Published in Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams, Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
Meheshinder Singh, Kemal I. Deen
Once ingested, excystation occurs in the small intestine and trophozoites are released which then migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts. Both cysts and trophozoites are passed in the faeces. The cysts can survive for days to weeks in the external environment and are responsible for transmission, whereas the trophozoites are rapidly destroyed. In many cases, the trophozoites remain confined to the intestinal lumen (non-invasive infection) of individuals who are asymptomatic carriers, who pass cysts in the stool. In some patients the trophozoites invade the intestinal mucosa (intestinal disease) or through the bloodstream to extraintestinal sites such as the liver, brain and lungs (extraintestinal disease), with resultant pathologic manifestations. The invasive and non-invasive forms represent two separate species, E. histolytica and E. dispar, respectively. These two species are morphologically indistinguishable unless E. histolytica is observed with ingested red blood cells (erythrophagocystosis). Transmission can also occur through exposure to faecal matter during sexual contact (in which case not only cysts, but also trophozoites could prove infective).
Rose Bengal-Mediated Photodynamic Antimicrobial Treatment of Acanthamoeba Keratitis
Published in Current Eye Research, 2020
Hatice Tuba Atalay, Betül Seher Uysal, Fakhriddin Sarzhanov, Selma Usluca, Nilüfer Yeşilırmak, Mehmet Cüneyt Özmen, Sidre Erganiş, Atike Burçin Tefon, Funda Dogruman-Al, Kamil Bilgihan
Trophozoites of A. castellanii genotype T4 strain (GenBank accession number: EF429131) were originally isolated from corneal scraping samples obtained from a patient with AK. In brief, trophozoites were cultivated in tissue culture flasks containing 20 mL of PYG (protease peptone, yeast extract, and glucose,) at 30°C for 7 days. Trophozoites in the logarithmic growth phase were centrifuged at 500 g for 10 min. Pelleted amoebae were washed and resuspended in sterile Neff’s saline solution (1.2 g NaCl, 0.4 g MgSO4. H2O, 0.4 g CaCl2.2H2O, 1.42 g Na2HPO4, 1.36 g KHPO4) in 100 mL distilled water. The numbers of viable trophozoites and cysts were determined using the trypan blue dye exclusion method and a Neubaurerr hemacytometer. Experimental amoebae were placed in Neff’s saline solution after adjusting the concentration to 1.3 × 105 cells/mL (80% trophozoites, 20% cysts).
Curcuma longa ethanol extract and Curcumin inhibit the growth of Acanthamoeba triangularis trophozoites and cysts isolated from water reservoirs at Walailak University, Thailand
Published in Pathogens and Global Health, 2020
Watcharapong Mitsuwan, Chooseel Bunsuwansakul, Theodore Ebenezer Leonard, Sawanya Laohaprapanon, Kruawan Hounkong, Kingkan Bunluepuech, Chalermpon Kaewjai, Tooba Mahboob, Chandramathi Sumudi Raju, Mahaveer Dhobi, Maria de Lourdes Pereira, Muhammad Nawaz, Christophe Wiart, Abolghasem Siyadatpanah, Roghayeh Norouzi, Veeranoot Nissapatorn
Anti-Acanthamoeba activity of the extracts against the trophozoites and cysts of Acanthamoeba spp. was determined as described [14] with minor modification. The trophozoites and cysts were cultured as described above. Each of trophozoites and cysts was adjusted to a final concentration of 2 × 105 cells/mL. One hundred microliters of the parasite suspension were added into 96 well microtiter plates, containing 100 µL of serially diluted extract. The plates were incubated at room temperature for 24 h. One percent DMSO was included as a negative control. Inhibitory activity was carried out using a trypan blue exclusion assay. The relative percentage of parasite viability was defined as (mean of the treated parasite/mean of the control) × 100. Meanwhile, the morphology of the trophozoite and cyst forms of A. triangularis after treatment with C. longa extract was investigated preliminarily by inverted microscopy.
Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis
Published in Clinical and Experimental Optometry, 2021
Lily Ho, Isabelle Jalbert, Kathleen Watt, Alex Hui
Treatment for Acanthamoeba keratitis is complicated as Acanthamoeba exists in two forms: active trophozoites and dormant cysts.61 While trophozoites are sensitive to many agents, cysts are hardy and hence difficult to treat and eliminate.61 Biguanides (such as polyhexamethylene biguanide PHMB and chlorhexidine) are found to be the most effective cysticidal agents.104 Other main cysticidal agent options are diamidines (propamidine isethionate and hexamidine).13,61 Treatment for Acanthamoeba keratitis is generally off-label and not standardised but supported from case series evidence, with limited amounts of high-level evidence although reviews and recommendations are available.105