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Entamoeba histolytica
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
William A. Petri, Jonathan I. Ravdin
Amebas from clinical isolates can be maintained in long-term culture by adapting them to monoxenic culture with a single bacterial or trypanosomatid associate. Entamoeba coli and E. hartmanni must be maintained in monoxenic culture, as they have never been grown successfully in axenic culture (68). Axenic culture is the ideal medium in which to maintain E. histolytica for scientific study. Diamond, in 1961, first described axenic cultivation of E. histolytica (11). The medium currently in use is TYI-S-33 (trypticase-yeast extract-ironserum) (68,70). The source of the trypticase, which is a pancreatic digest of casein, is essential for success in cultivation, as most commercial casein digests will not support the growth of Entamoeba (68). The digest currently used in TYI-S-33 is casein digest peptone (catalog #97023, BBL Microbiology Systems, Cockeysville, MD). A major disadvantage of axenic culture is the inability of the parasite to encyst (68).
Cultivation of Entamoeba Histolytica
Published in Roberto R. Kretschmer, Amebiasis: Infection and Disease by Entamoeba histolytica, 2020
The ability to maintain a cell in vitro is critical to the experimental manipulation of that cell in the laboratory. And while it is true for most cells that such manipulation is best conducted in the absence of all other metabolizing cells, i.e., axenic culture,1 it is not wholly true for Entamoeba histolytica. This parasite’s normal habitat is the human colon, an environment teeming with bacteria and fungi. It follows then that investigations of the role played by these microbes, for example, in the nutrition or pathogenicity of the amebas are best performed in the presence of one microbial associate (monoxenic culture),1 or multiple associates (xenic culture).1 However, with the advent of axenic cultures investigators are in a better position to conduct such studies since they can now add the bacteria to the system under precisely controlled conditions.
In Vitro Studies on Chemical Regulation of Gametangial Formation in Bryophytes
Published in R. N. Chopra, Satish C. Bhatla, Bryophyte Development: Physiology and Biochemistry, 2019
In recent years considerable work has been done on chemical regulation of sexual reproduction in bryophytes grown in vitro. Although the conditions of growth in axenic cultures are in some ways far from natural, it is hoped that ultimately the data obtained in artificial conditions will be helpful in understanding the way sexual reproduction is regulated in vivo. The significance of responses to applied chemicals has its basis in the fact that all the major growth regulators have been reported in bryophytes.
Inhibitory effect of Tunceli garlic (Allium tuncelianum) on blastocystis subtype 3 grown in vitro
Published in Expert Opinion on Orphan Drugs, 2020
Mehmet Aykur, Emrah Karakavuk, Muhammet Karakavuk, Mesut Akıl, Hüseyin Can, Mert Döşkaya, Yüksel Gürüz, Hande Dağcı
To date, many in vitro studies have been performed on the effects of drugs against Blastocystis using various types of xenic cultures [49–51]. In this study, all Blastocystis subtype 3 used were isolated from patients and cultured with the associated bacteria. The condition of these strains’ growth in this medium resemble more like to their normal habitat in the gut. On the other hand, there are some problems when using axenic cultures for in vitro drug testing of Blastocystis isolates. Axenic cultures are not practical for clinical laboratories as they require a lot of time and are expensive. Also, eliminating the bacteria that act as a food source for Blastocystis can alter the properties of the culture. On the other hand, Blastocystis can be grown in less than 1 week in xenic culture. As a result of eliminating the necessary bacteria for the growth of Blastocystis or a applies equally to the axenization procedure, it is argument that may be sensitive to some drugs [53–55]. When ethanolic extract of A. tuncelianum was added to the culture medium, it was not changing the culture medium pH. In addition, another study showed that the ethanolic extract of garlic is more effective than the extract obtained from water [56].
In vitro drug discovery models for Mycobacterium tuberculosis relevant for host infection
Published in Expert Opinion on Drug Discovery, 2020
Drug discovery programs require robust and reliable primary and secondary screening assays, both to identify hits and to drive the discovery process. Key elements of a successful assay include reproducibility, capacity, ease of use, rapid assay turnaround, and relevance to the disease. This combination is difficult to achieve for tuberculosis, given a combination of the slow growth rate of the organism, the requirement to work in a controlled environment, and the complexity of the disease pathology. The simplest in vitro assays tend to have the least relevance for the infection setting. For example, they focus heavily on generating rapidly growing organisms in axenic culture. The development of truly reflective models would require heterogenous bacterial populations in different physiological states, but by their nature, these are the hardest in which to develop reliable data. A compromise between the two extremes has led to the development of increasingly sophisticated in vitro models, in which different aspects of infection can be modeled or mimicked.
Advances in preclinical approaches to Chagas disease drug discovery
Published in Expert Opinion on Drug Discovery, 2019
Fernando Villalta, Girish Rachakonda
T. cruzi multiplies well inside host cells [20,21], which permits the identification of drugs that kill the parasite and those that inhibit growth and division. However, as T. cruzi evades the immune system during chronic infection, drugs that kill the parasite intracellularly are essential for eliminating Chagas. Therefore, hits need to be followed up in a parasite killing assay. One solution to the low throughput is to use an axenic (free growing) amastigote assay as the primary screen [121]. Axenic amastigotes do not occur naturally, so care must be taken in interpreting the data. Such assays also need to be designed to only identify cytocidal compounds to prevent false positives as reported [20,21]. Hits can then be confirmed in an intracellular assay.