Background There is increasing evidence suggesting the existence of an interaction between commensal microbiota, the gut and the brain. The aim of this study was to examine the influence of commensal microbiota on the host behaviors in a contaminationfree environment, which was verified by culture-based methods. Methods Open-field and marble-burying tests were used to analyze anxiety-like behaviors and locomotor activity in gnotobiotic BALB/c mice with a common genetic background in a sterile isolator. The monoamine levels in several regions of the brain were measured in germfree (GF) mice and commensal fecal microbiota-associated mice (EX-GF). Key Results A 24-h exposure to the environment outside the sterile isolators rendered GF mice less anxious than those not contaminated, while there was no change in the locomotion. EX-GF mice, the gnotobiotic mice with normal specific pathogen-free microbiota, were less anxious and active than GF mice using open-field and marble-burying tests. The norepinephrine, dopamine, and serotonin turnover rates were higher in the EX-GF mice than in the GF mice in most regions of the brain, suggesting that monoaminergic neurotransmission might increase in the EX-GF mice comparing the GF mice. Monoassociation with Brautia coccoides reduced the anxiety level, but it did not affect the locomotor activity. In contrast, colonization with Bifidobacterium infantis decreased the locomotor activity, while having little effect on the anxiety level. Conclusions & Inferences These results strongly support the current view that gut microorganisms modulate brain development and behavior.

In moderate-severe CAP, administration of corticosteroids promotes resolution of clinical symptoms and reduces the duration of intravenous antibiotic therapy.

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Anorexia nervosa (AN) results in gut dysbiosis, but whether the dysbiosis contributes to AN-specific pathologies such as poor weight gain and neuropsychiatric abnormalities remains unclear. To address this, germ-free mice were reconstituted with the microbiota of four patients with restricting-type AN (gAN mice) and four healthy control individuals (gHC mice). The effects of gut microbes on weight gain and behavioral characteristics were examined. Fecal microbial profiles in recipient gnotobiotic mice were clustered with those of the human donors. Compared with gHC mice, gAN mice showed a decrease in body weight gain, concomitant with reduced food intake. Food efficiency ratio (body weight gain/food intake) was also significantly lower in gAN mice than in gHC mice, suggesting that decreased appetite as well as the capacity to convert ingested food to unit of body substance may contribute to poor weight gain. Both anxiety-related behavior measured by open-field tests and compulsive behavior measured by a marble-burying test were increased only in gAN mice but not in gHC mice. Serotonin levels in the brain stem of gAN mice were lower than those in the brain stem of gHC mice. Moreover, the genus Bacteroides showed the highest correlation with the number of buried marbles among all genera identified. Administration of Bacteroides vulgatus reversed compulsive behavior but failed to exert any substantial effect on body weight. Collectively, these results indicate that AN-specific dysbiosis may contribute to both poor weight gain and mental disorders in patients with AN.

ABSTRACT:The aim of this study was to examine the influence of maternal intestinal and vaginal bifidobacteria on the establishment of bifidobacteria colonizing the gut in infants. Fecal samples from 110 healthy pregnant mothers within 1 mo before delivery and their babies at 1 mo of age and 100 vaginal swabs from the mother within 7 d before delivery were collected at a maternity hospital in Fukuoka city, Japan. The fecal and vaginal samples were assayed by PCR to detect Bifidobacterium species and by real-time PCR assays to estimate the bifidobacterial number. The detection of Bifidobacterium breve in the mothers' feces was significantly associated with increases in both the bifidobacterial counts and number of Bifidobacterium species in the babies' feces. In addition, a cesarean section was significantly associated with both a decrease in the counts and diversity of bifidobacteria in the babies' feces. The number of Bifidobacterium species detected in the vaginal swabs of mothers were not associated with either the bifidobacterial counts or the diversity of bifidobacteria in the babies' feces. The most important determinants of intestinal bifidobacteria in infants were the colonization of B. breve in the mothers' gut and vaginal delivery.