Search

Ampicillin is applied in rodents to induce a temporarily depleted microbiota. To elucidate whether bacteria are just temporarily suppressed or fully eliminated, and how this affects the re-colonisation process, we compared the microbiota and immune system in conventionally housed untreated mice with newly weaned ampicillin treated mice subsequently housed in either a microbe containing environment or in an isolator with only host associated suppressed bacteria to recolonize the gut. Two weeks ampicillin treatment induced a seemingly germ-free state with no bacterial DNA to reveal. Four weeks after treatment caeca were still significantly enlarged in both treated groups, but bacteria re-appeared even in isolator housed mice. While some suppressed bacteria were able to recover and even dominate the community, the abundances and composition were far from the untreated mice and differed between isolator and conventional housing. The treatment reduced the innate cytokine expressions at least for three weeks after treatment, and had a non-lasting reducing impact on the regulatory T cells, and a more lasting impact on the natural killer T cells. We conclude that temporary ampicillin treatment suppresses the majority but does not eliminate all the gut microbiota members. The re-colonisation process is as such influenced by both suppressed host associated bacteria and by environmental bacteria. Treated mice do not re-obtain a complex gut microbiota comparable to untreated mice, and the immune response and gut morphology reflect this. This is a concern when comparing host parameters sensitive to microbial regulation after an antibiotic-induced temporarily "germ-free" state., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Transferring gut microbiota from one individual to another may enable researchers to "humanize" the gut of animal models and transfer phenotypes between species. To date, most studies of gut microbiota transfer are performed in germ-free mice. In the studies presented, it was tested whether an antibiotic treatment approach could be used instead. C57BL/6 mice were treated with ampicillin prior to inoculation at weaning or eight weeks of age with gut microbiota from lean or obese donors. The gut microbiota and clinical parameters of the recipients was characterized one and six weeks after inoculation. The results demonstrate, that the donor gut microbiota was introduced, established, and changed the gut microbiota of the recipients. Six weeks after inoculation, the differences persisted, however alteration of the gut microbiota occurred with time within the groups. The clinical parameters of the donor phenotype were partly transmissible from obese to lean mice, in particularly β cell hyperactivity in the obese recipients. Thus, a successful inoculation of gut microbiota was not age dependent in order for the microbes to colonize, and transferring different microbial compositions to conventional antibiotic-treated mice was possible at least for a time period during which the microbiota may permanently modulate important host functions.