Abstract
The gut microbiota has a central influence on human health. Microbial dysbiosis is associated with many common immunopathologies such as inflammatory bowel disease, asthma and arthritis. Thus, understanding the mechanisms underlying microbiota-immune system crosstalk is of crucial importance. Antibiotic administration, while aiding pathogen clearance, also induces drastic changes in the size and composition of intestinal bacterial communities which can have an impact on human health. Antibiotic treatment in mice recapitulates the impact and long-term changes in human microbiota from antibiotic treated patients, and enables investigation of the mechanistic links between changes in microbial communities and immune cell function. While several methods for antibiotic treatment of mice have been described, some of them induce severe dehydration and weight-loss complicating the interpretation of the data. Here, we provide two protocols for oral antibiotic administration which can be used for long-term treatment of mice without inducing major weight-loss. These protocols make use of a combination of antibiotics that target both Gram-positive and Gram-negative bacteria and can be provided either ad libitum in the drinking water or by oral gavage. Moreover, we describe a method for the quantification of microbial density in fecal samples by qPCR which can be used to validate the efficacy of the antibiotic treatment. The combination of these approaches provides a reliable methodology for the manipulation of the intestinal microbiota and the study of the effects of antibiotic treatment in mice.
Highlights
The mammalian gastrointestinal mucosa is a unique environment colonized by a highly complex mixture of microorganisms that establish a mutualistic relationship with the host
The gut microbiota can be altered by various factors, but perhaps the most drastic changes are induced by antibiotic treatment that severely alters both the size and composition of bacterial communities[3,4]
When mice are treated with antibiotics ad libitum in the drinking water, they lose weight (~10%) within the first few days of antibiotic administration, but recover normal weight gain thereafter (Figure 1)
Summary
The mammalian gastrointestinal mucosa is a unique environment colonized by a highly complex mixture of microorganisms that establish a mutualistic relationship with the host. Several reports have shown that administration of antibiotics on the drinking water ad libitum results in very noticeable weight loss as mice refrain from drinking water, presumably due to its foul taste[5,6] In these models the severe dehydration concomitant to oral antibiotic administration may complicate the interpretation of experiments aiming to identify the effect of antibiotic treatment in immune cell function. We present a detailed step-by-step account of two distinct protocols for oral antibiotic administration to mice, fecal sample collection, DNA extraction, preparation of standards and quantification of bacteria in fecal samples by qPCR These protocols provide a reliable method to manipulate the intestinal microbiota in mice and to study of the effects of antibiotic treatment in intestinal homeostasis and disease. Prior to beginning any animal procedure, ensure that the appropriate permissions are obtained through the local institution/organization
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