Bacterial species that have traditionally been regarded as safe are used in probiotics; the main strains used include lactic acid bacteria and bifidobacteria that inhabit the intestinal tracts of humans and animals. However, reports of frequent isolation of bacteria used in probiotics from infection sources in recent years have raised much debate over the safety of probiotics. This article describes the status quo of isolation of probiotic bacteria from infections and reviews each of the factors that have to be addressed in assessing the safety of probiotics, namely pathogenicity, infectivity, toxicity, and intrinsic properties of the bacteria. Monoassociation with Bifidobacterium longum in gnotobiotic mice as a method to assess safety with respect to infection, and translocation and immune responses as a result of the monoassociation are also described.

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Germ-free ICR mice monoassociated with Bifidobacterium longum (GB mice) lived longer than non-treated germ-free (GF) mice after intragastric or intravenous (i .v.) administration of a high dose of viable E. coli, or i.v. injection of endotoxin. The number of viable E. coli and the endotoxin level in various organs at 24 hr postinjection were significantly lower in GB than GF mice. Antilethal activity was not elicited by the feeding of heat-killed B. longum. The antilethal effect was observed 3, but not less than 2, weeks after the association of B. longum. Furthermore, the effect was not observed when GF-athymic nude mice (BALB/c background) were used. After intragastric administration of a sublethal dose , the number of viable E. coli in organs of GB mice decreased to an undetectable level within 7 days , while the organisms were persistently isolated in GF mice. In both groups, many (109 v.c./g) E. coli persisted in the intestine. These results suggest that B. longum organisms monoassociated with GF mice generate systemic resistance to the invading E. coli, and increase the resistance to the lethal activity of endotoxin .

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Orexins are neuropeptides that play a role in maintaining wakefulness and contribute to central regulation of cardiovascular function. This first multicenter, randomized, double‐blind study investigated the effects of suvorexant, a reversible dual orexin receptor antagonist, on nighttime blood pressure (BP) in patients with insomnia and hypertension. After a 4‐week run‐in period, adult outpatients (n = 82) with treated hypertension (clinic SBP <160 mm Hg) and insomnia were treated with suvorexant 20 mg/d or placebo before bedtime for 2 weeks. Twenty‐four‐hour ambulatory BP monitoring was performed at baseline and the end of treatment, and home BP measurements (morning and evening) were taken daily. Nighttime systolic BP (SBP), the primary endpoint, decreased slightly from baseline to week 2 in both the suvorexant and placebo groups (−4.4 vs −1.8 mm Hg; P = 0.494). Clinic, 24‐hour, daytime and morning SBP (ambulatory blood pressure monitoring) also decreased slightly and similarly from baseline in both groups. In this study, suvorexant had no overall effect on BP in patients with insomnia and treated hypertension.