Strongyloidiasis
Peter D. Walzer, Robert M. Genta in Parasitic Infections in the Compromised Host, 2020
Cutaneous penetration of filariform larvae found in contaminated soil is the most common way by which human strongyloidiasis is acquired. The ingestion of infective larvae is not believed to be a common mode of transmission in humans, although coprophagia may play an important role in dogs. In some reported cases, S. stercoralis has been transmitted in unusual manners, such as through renal transplantation (105) or apparently from immersion in a swimming pool (106), but these events represent little more than medical curiosities. Transmammary transmission during breast feeding, a well-documented mode of infection for S. ratti in rodents (107), appears to occur occasionally in human S. fulleborni infections (108) but has not been observed for S. stercoralis.
Commensal microbiota and its relationship to homeostasis and disease
Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald in Principles of Mucosal Immunology, 2020
Since the 1960s it has been consistently noted that germ-free mice have numerous immunologic, physiologic, and anatomical differences from conventionally reared animals (Table 19.1). They require more calories because they lose the nutrients provided by microbial degradation of plant material in mouse chow. And mice are coprophagic (ingest feces of other cohoused individuals). The small intestine is longer and the villi in the duodenum are longer than in normal mice but shorter in the ileum. The ceca of germ-free mice are grossly enlarged. There is poor development of gut-associated lymphoid tissue, including Peyer's patches which only contain primary follicles. Unlike conventionally colonized mice, few T cells can be found infiltrating the intestinal lamina propria, and there is an almost complete absence of secretory IgA. Intraepithelial lymphocyte numbers are very low, although there are more γδ T cells than αβ T cells. TLR and major histocompatibility class II expression on intestinal epithelial cells is also markedly reduced in germ-free animals, reflecting the reduced need for antigen detection and presentation.
Gross Physiological Effects in Higher Animals
Stephen P. Coburn in The Chemistry and Metabolism of 4′-Deoxypyridoxine, 2018
In mice, Miller329 used a B6-deficient diet supplemented with 0.5% succinylsulfathiazole to reduce intestinal flora and 0.1% 4′-deoxypyridoxine. The authors mention preventing coprophagy but apparently assumed that wire floors were adequate for this purpose. Additional precautions are usually necessary. Administration of succinylsulfathiazole on days 10 to 14 did not increase the incidence of cleft palate over that produced by the deficient diet alone. Combining succinylsulfathiazole with deoxypyridoxine during days 10 to 14 caused 61% of the fetuses to have cleft palate with 83% of the litters containing at least one affected fetus. This is a marked increase from 21% affected fetuses with at least one affected pup in 50% of the litters observed with the deficient diet alone. Extending the succinylsulfathiazole treatment to include days 1 to 15 with deoxypyridoxine added on days 10 to 14 produced 100% affected fetuses. Since no group received only the succinylsulfathiazole over days 1 to 15, it is impossible to determine the relative importance of the deoxypyridoxine in producing these last results. The treatments did not change the mean litter size or rate of resorption. The author also found that a dietary pyridoxine deficiency seemed to aggravate the teratogenic action of cortisone.
Guidelines for reporting on animal fecal transplantation (GRAFT) studies: recommendations from a systematic review of murine transplantation protocols
Published in Gut Microbes, 2021
Kate R. Secombe, Ghanyah H. Al-Qadami, Courtney B. Subramaniam, Joanne M. Bowen, Jacqui Scott, Ysabella Z.A. Van Sebille, Matthew Snelson, Caitlin Cowan, Gerard Clarke, Cassandra E. Gheorghe, John F. Cryan, Hannah R. Wardill
The need for better guidance of preclinical FMT protocols is underscored by the additional layers of complexity that are introduced in a preclinical setting. For example, experimental design, preparation and administration are complicated by the coprophagic nature of rodents. While some studies have exploited this behavior (co-housing to induce microbial transfer),8 there is significant variability in how this technique is applied and the omission of key methodological detail hinders experimental replication, thus undermining subsequent translation.9 Similarly, while bowel preparation is recommended for colonoscopically administered FMT in humans, the necessity for an appropriate equivalent in recipient rodents remains unclear.
Complex interactions between the microbiome and cancer immune therapy
Published in Critical Reviews in Clinical Laboratory Sciences, 2019
Drew J. Schwartz, Olivia N. Rebeck, Gautam Dantas
Designing in vivo microbiome-related experiments is accompanied by its own set of challenges and considerations. If humanized mice are used, will they be derived from germ-free mice or antibiotic-treated mice? Germ-free mice are free of all currently detectable microorganisms and allow complete recolonization, but they are expensive to maintain, have severely underdeveloped immune systems that are not always restorable, and must be individually derived for unique genotypes [48,49]. If antibiotic-treated mice are used, which antibiotic(s) will be used to deplete the conventional mouse microbiota, and what confounding effects may they produce? Individual antibiotics and antibiotic cocktails affect different microbial populations and have varying efficacy and tolerability in mice [48]. Even seemingly arbitrary decisions require due diligence. Considering the appropriate vendor and housing conditions for isogenic conventional mice is vital because microbiota compositions differ among mice that are obtained from different suppliers and that are housed in different facilities [50]. Once mice are obtained and appropriately humanized, it is important to ensure they are consistently colonized and that their microbiota are stably established over time with minimal strain dropout [45–47]. For short experiments, this can be done by cohousing animals, wherein they will engage in coprophagy and exchange microbiota content [51]. For longer studies, littermate crossing can aid in microbiome stability between cages [51,52]. All these factors must be taken into consideration not only when designing experiments, but also when interpreting results, reading the literature, and extrapolating conclusions from animal studies about the role of the microbiota in human health.
Reversal of temperature responses to methylone mediated through bi-directional fecal microbiota transplantation between hyperthermic tolerant and naïve rats
Published in Temperature, 2022
Robert Goldsmith, Amal Aburahma, Sudhan Pachhain, Sayantan Roy Choudhury, Vipa Phuntumart, Ray Larsen, Christopher S. Ward, Jon E. Sprague
Male rats were randomly assigned into two groups of six (6) each, the first group being the treatment group and the second serving as the saline controls. On testing day, all subjects were weighed prior to drug challenge, and a core temperature reading was taken with a rectal thermometer at time zero. On treatment days, the ambient temperature averaged 27.4 ± 0.12°C. Following the first temperature measurement each week, the male treatment group received a 10 mg/kg subcutaneous (sc) dose of methylone, and the control group received an equal volume of saline solution. In order to induce tolerance to the methylone-induced hyperthermia, one group of animals were treated with methylone once a week for 4 weeks. This treatment group was referred to as the methylone hyperthermic-tolerant (MHT) group. The second treatment group was treated with saline once a week for 4 weeks. This treatment group was referred to as the methylone-naïve (MN) group [19]. Between weeks 3 and 4, fecal droppings were collected for the FMT from both the MHT and MN groups, with reciprocal transplantations then performed. Therefore, all animals experienced coprophagy under identical circumstances. The first day of FMT was considered day 0 and served as the fecal composition baseline for each group. After 7 days of FMT, the fecal droppings were again collected to determine differences before (day 0) and after (day 7) FMT. Following drug treatment, core temperature readings were recorded at the 30-, 60- and 90-minute time points. This treatment schedule was maintained once a week for a total of four consecutive weeks, until the hyperthermic response of the methylone treatment group was statistically insignificant. Those animals treated weekly for four weeks with methylone were designated as MHT and those that received only saline for four weeks were designated MN. Figure 1 depicts the study design. Rectal temperatures were measured in all animals using a Physiotemp Thermalert TH-8 thermocouple (Physitemp Instruments, Clifton, NJ) attached to a RET-2 (rat) rectal probe coated with white petrolatum prior to insertion. RET-2 probes were inserted 5 cm into the rectum, where they remained for at least fifteen seconds, until a stable temperature was obtained.
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