Can a new medium improve detection of hydrogen peroxide-producing lactobacilli?

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A healthy vaginal ecosystem has been shown to protect against acquisition of human immunodeficiency virus and gonorrhea. Women colonized with hydrogen peroxide (H2O2)-producing lactobacilli are more likely to maintain normal vaginal flora than women whose lactobacilli do not produce H2O2.

The study aimed to formulate a testing medium that would support growth and H2O2 detection across a broader range of lactobacilli than the published, widely used TMB agar formulation. The new medium, TMB-Plus, contains brucella agar base, 3,3',5,5'-tetramethylbenzidine, horseradish peroxidase, starch, vitamin K, hemin, magnesium sulfate, manganese sulfate, and horse serum. To validate it, researchers inoculated 256 vaginal isolates and ATCC strains onto TMB-Plus and, for comparison, TMB.

On TMB-Plus, 69% of isolates showed enhanced growth and 48% showed enhanced color production. The percentage of H2O2-positive isolates rose from 71% on TMB to 79% on TMB-Plus. Formulations combining Rogosa or MRS agar base with peroxidase and a chromogen did not support growth of all Lactobacillus strains and detected fewer H2O2-producing strains than TMB-Plus. The researchers concluded that TMB-Plus better supports growth of a wider range of Lactobacillus strains isolated from the vagina and enhances color production by H2O2-producing strains.