LAMVAB - A new selective medium for the isolation of lactobacilli from faeces

The development of a new selective medium, LAMVAB, for the isolation of Lactobacillus species from faeces is described. The medium is highly selective due to a low pH and the presence of vancomycin (20 mg l(-1)). In addition, the medium contains cysteine-HCl to enhance anaerobic conditions, and bromocresol green as a pH indicator. Competing faecal flora is inhibited by the low pH (enterobacteria, bacteroides and other Gram-negative anaerobes, clostridia) and the vancomycin (enterococci, bifidobacteria, clostridia). Characterization of the strains isolated on LAMVAB from human faeces included all common faecal lactobacilli and no other lactic acid bacteria. In one sample, vancomycin-resistant cocci were present and in another sample, yeasts were isolated. It can be concluded that the new medium is highly selective and permits the growth of all common faecal lactobacilli. The new medium can also be appl:ed as a selective medium for lactobacilli in probiotics, which contain mixed populations of lactobacilli, bifidobacteria and enterococci. (C) 1997 Elsevier Science B.V.