Lactobacillus fermentum Ess-1 with unique growth inhibition of vulvo-vaginal candidiasis pathogens.

The aim of this study was to characterize human isolates of Lactobacillus species for their capacity to interfere with the growth of different strains of Candida species in vitro in the search for a potential probiotic. Growth inhibition of Candida species was screened using an agar-overlay method. Inhibiting strains were selected to assay the effect of a cell-free Lactobacillus culture filtrate (LCF) on the growth of isolates of Candida albicans and Candida glabrata. A total of 126 human Lactobacillus isolates was investigated. Eighteen isolates significantly inhibited the growth of C. albicans on agar. The LCF of one of these strains showed strong inhibition of both C. albicans and C. glabrata. This strain was genetically identified as Lactobacillus fermentum and designated L. fermentum Ess-1. Further tests to evaluate the probiotic potential of this strain indicated that L. fermentum Ess-1 strain is a promising probiotic for use in clinical trials to treat and prevent vulvo-vaginal candidiasis.

Is hydrogen peroxide responsible for the inhibitory activity of alpha-haemolytic streptococci sampled from the nasopharynx?

OBJECTIVE: The inhibitory effect of alpha-haemolytic Streptococci (AHS) in vitro on the three commonest otitis media pathogens, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, was previously investigated. The aim of this study was to determine the mechanism of this inhibitory activity. MATERIAL AND METHODS/RESULTS: When fractions of AHS filtrate were assayed to determine their inhibitory activity after size-exclusion chromatography, the inhibitory activity was found in the fractions with a low molecular weight. The inhibitory effect was completely reversed when catalase was added to the cell-free filtrate of AHS. A quantitative method also revealed high production (approximately 3 mmol/l) of hydrogen peroxide in the AHS filtrate with the best inhibitory activity. Electron microscopy of bacteria exposed to AHS filtrate with an inhibitory effect showed changes similar to bacteria exposed to hydrogen peroxide. CONCLUSIONS: We conclude that the inhibitory effect of AHS is most likely due to the production of hydrogen peroxide. The significance of hydrogen peroxide production of AHS is discussed in relation to the non-specific and specific mucosal defence systems.