Entamoeba histolytica
Peter D. Walzer, Robert M. Genta in Parasitic Infections in the Compromised Host, 2020
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).
Alternaria
Dongyou Liu in Laboratory Models for Foodborne Infections, 2017
The isolation and identification of Alternaria species from food products is based on traditional methods including culturing under standardized conditions and observation of morphological characteristics. Besides being laborious, time consuming, and sometimes restricted to experts in this field, this identification scheme is difficult owing to variations within the same species as the morphological characteristics are very sensitive to the cultural conditions. The most recent taxonomic keys, as reviewed by Simmons1 in his identification manual, provide descriptions and illustrations of at least 296 taxa, based on the examination of stable isolates in axenic culture. The isolates are cultured in potato carrot agar (PCA) and V8 agar and incubated for 7 days at 23°C under an alternating light/dark cycle consisting of 8 h of cool-white fluorescent daylight and 16 h darkness so as to observe morphological characteristics (Figure 30.1).
Entamoeba histolytica
Dongyou Liu in Handbook of Foodborne Diseases, 2018
A key aspect of the biology of E. histolytica trophozoites is their process of cell division, which differs from that of other eukaryotes. Amoebic axenic culture consists of mixed cells of one or more nuclei, and in turn, the DNA content of each nucleus is unique. Eukaryotic chromosome segregation is orchestrated by the microtubule (MT) organizing center. In E. histolytica, the process is regulated by MT assemblies (MTAs) including mono, bi-, and multipolar spindles for DNA segregation, suggesting that it occurs on different kinds of MT structures and requires the presence of several genome copies in a single nucleus.29 Cytokinesis has been reported to occur in three ways. For the first, an intercellular bridge is formed and extends and cleaves in random sites. The second depends on the presence of helper cells that participate in the bridge rupture; this mechanism has not been identified. Finally, as cytokinesis failures are common, the process can lead to the formation of amoebae that contain multiple nuclei.29
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.
Host-microbe interactions and the behavior of Caenorhabditis elegans
Published in Journal of Neurogenetics, 2020
Dennis H. Kim, Steven W. Flavell
The experimental study of C. elegans has typically involved laboratory cultivation on monoaxenic lawns of Escherichia coli OP50 seeded on agar plates supplemented with cholesterol (Brenner, 1974). Genetic and metabolomic characterization of alternative bacterial food sources for C. elegans, such as Comamonas, Bacillus subtilis and mutants of E. coli, has defined conserved requirements for micronutrients (Qi, Kniazeva, & Han, 2017; Watson et al., 2014), novel mechanisms of host co-option of bacterial siderophores for iron acquisition (Qi & Han, 2018), and metabolic determinants of bacteria that can influence complex phenotypes such as lifespan (Han et al., 2017; Qi & Han, 2018; Saiki et al., 2008; Virk et al., 2012). Semi-defined axenic media has been developed for growth and cultivation of C. elegans, but live bacteria support optimal growth and development (Lenaerts, Walker, Van Hoorebeke, Gems, & Vanfleteren, 2008).
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