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Segmented filamentous bacteria (SFB) modulate the ontogeny of the immune system, and their presence can significantly affect mouse models of disease. Until recently, the inability to successfully culture SFB has made controlled studies on the mechanisms by which these bacteria exert their influence problematic. Here, we report a new method for selecting SFB from complex microbial mixtures, providing researchers a simple and cost-effective means to prepare pure infective inocula for prospective studies and also to compare individual SFB isolates.

Germ-free mice are used to examine questions about the role of the gut microbiota in development of diseases. Generally these animals are maintained in semi-rigid or flexible-film isolators to ensure their continued sterility or, if colonized with specific microbiota, to ensure that no new species are introduced. Here, we describe the use of a caging system in which individual cages are hermetically sealed and have their own filtered positive airflow. This isopositive caging system requires less space and reduces animal housing costs. By using strict sterile techniques, we kept mice germ-free in this caging system for 12 weeks. We also used this caging system and approach to conduct studies evaluating a) the stability of the microbiome in germ-free mice receiving a fecal transplant and b) the stability of dietary-induced microbiota changes in fecal-transplanted mice. As has been shown in fecal transfer studies in isolators, we found that the transferred microbiota stabilizes as early as 2 weeks post transfer although recipient microbiota did not completely recapitulate those of the donors. Interestingly, we also noted some sex effects in these studies indicating that the sex of recipients or donors may play a role in colonization of microbiota. However, a larger study will be needed to determine what role, if any, sex plays in colonization of microbiota. Based on our studies, an isopositive caging system may be utilized to test multiple donor samples for their effects on phenotypes of mice in both normal and disease states even with limited available space for housing.

Background: Rosette-forming glioneuronal tumour (RGNT) is a rare and novel brain tumour. We present a case of rosette forming glioneuronal tumour of the fourth ventricle and highlight the imaging and histological features of this tumour entity. We also performed a comprehensive review of the imaging features, treatments and outcomes of all past cases and make recommendations on diagnosis and management., Method: We conducted a PUBMED search using the words 'rosette forming glioneuronal tumour', and identified 48 cases of rosette forming glioneuronal tumour. We reviewed the location, imaging features of this rare tumour entity as well as the treatment and follow-up. We also present a case of a 42-year-old man with an incidental finding of a solid-cystic midline mass in the posterior fossa at the level of fourth ventricle with morphological features and immunohistochemical characteristic of a RGNT (WHO Grade I)., Findings: RGNT is commonly found in association with the fourth ventricle often with local extension; however, it is known to occur at sites outside of its usual location. RGNT can demonstrate solid, cystic or mixed features on MRI and frequently shows focal contrast enhancement. It is often associated with an element of hydrocephalus. Gross or subtotal tumour resection was the most common treatment of choice. Due to the intimate relationship of these tumours to key neural structures in the cerebellum, variable degrees of postoperative neurological deficits were reported in half of the patients. Among the reported cases, no evidence of recurrence following gross or subtotal resection of tumour was seen in the majority of patients. However, owing to lack of lengthy follow-up, we recommend routine imaging follow-up., Conclusion: Knowledge of this tumour is of importance as they are relatively slow growing and exhibit benign histological characteristics, thus depending on its location maybe amenable to gross total resection.