Growth inhibition of Staphylococcus aureus by H2O2-producing Lactobacillusparacasei subsp. paracasei isolated from the human vagina

H2O2 production by certain Lactobacillus strains is one of the mechanisms t hat helps to regulate the vaginal ecosystem. This paper describes the kinet ics of H2O2 production by two different strains of Lactobacillus paracasei subsp. paracasei under different culture conditions and the effect of this metabolite on the growth of Staphylococcus aureus. L. paracasei F2 produced 2.72 mmol l(-1) H2O2 while L. paracasei F28 produced 1.84 mmol l(-1). both in agitated cultures. Although L. paracasei F2 produced a higher H2O2 conc entration than L, paracasei F28, H2O2 production per number of live bacteri al cells was 10-fold higher for F28. The latter also showed a faster decrea se in viability during the stationary phase. There were no detectable level s of H2O2, in cultures without agitation. H2O2-producing lactobacilli inhib ited growth of S. aureus in a plaque assay and in mixed cultures, depending on the initial inoculum of the pathogen. (C) 1999 Federation of European M icrobiological Societies. Published by Elsevier Science B.V, All rights res erved.