Recently has been acknowledged the healthy use of Bacillus and related bacteria as probiotics. A mixture reported to contain four probiotic strains of Bacillus clausii is marketed as an OTC (Over The Counter) medicinal supplement for human use. Their poliantibiotic resistant property, useful for restoring the gut microbiota during antibiotic treatment, raises the question about the risk of resistance transfer. In order to better assess the risk-benefit ratio it is important to always monitoring the pattern and stability of resistance spectra in these bacteria. In this work, we have extensively redefined the antibiotic susceptibility profile of these four probiotic strains. Resistance phenotype has been determined by screening a large number of antibiotics, including natural products (such as penicillin, vancomycin and erythromycin), and completely synthetic molecules (such as fluoroquinolones). Extensive comparison with a wild type strain belonging to the normal intestinal microbiome was carried out. The molecular basis of some resistances was determined. Observed antibiotic resistances were correlated with previous and new data in safety evaluations of these strains for human use.

Actinomadura sp. ATCC 39727 produces the glycopeptide antibiotic A40926, structurally similar to teicoplanin, with significant activity against Neisseria gonorrhoeae and precursor of the semi-synthetic antibiotic dalbavancin. In this study the production of A40926 by Actinomadura under a variety of growth conditions was investigated. The use of chemically defined mineral media allowed us to analyze the influence of carbon and nitrogen sources, phosphate, ammonium and calcium on the growth and the antibiotic productivity of Actinomadura. We confirm recent data [Gunnarsson et al. (2003) J Ind Microbiol Biotechnol 30:150-156] that low initial concentrations of phosphate and ammonium are beneficial for growth and A40926 production, and we provide new evidence that the production of A40926 is depressed by calcium, but promoted when L-glutamine or L-asparagine are used as nitrogen sources instead of ammonium salts.

BackgroundThe spore-bearing alkaliphilic Bacillus species constitute a large, heterogeneous group of microorganisms, important for their ability to produce enzymes, antibodies and metabolites of potential medical use. Some Bacillus species are currently being used for manufacturing probiotic products consisting of bacterial spores, exhibiting specific features (colonization, immune-stimulation and antimicrobial activity) that can account for their claimed probiotic properties. In the present work a comparative proteomic study was performed aimed at characterizing the secretome of four closely related isogenic O/C, SIN, N/R and T B. clausii strains, already marketed in a pharmaceutical mixture as probiotics.ResultsProteomic analyses revealed a high degree of concordance among the four secretomes, although some proteins exhibited considerable variations in their expression level in the four strains. Among these, some proteins with documented activity in the interaction with host cells were identified, such as the glycolytic enzyme enolase, with a putative plasminogen-binding activity, GroEL, a molecular chaperone shown to be able to bind to mucin, and flagellin protein, a structural flagella protein and a putative immunomodulation agent.ConclusionThis study shows, for the first time, differences in the secretome of the OC, SIN, NR and T B. clausii strains. These differences indicate that specific secretome features characterize each of the four strains despite their genotypic similarity. This could confer to the B. clausii strains specific probiotic functions associated with the differentially expressed proteins and indicate that they can cooperate as probiotics as the secretome components of each strain could contribute to the overall activity of a mixed probiotic preparation.

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