Effect of hydrogen peroxide on growth of Candida, Cryptococcus, and other yeasts in simulated blood culture bottles

The addition of hydrogen peroxide to blood contained in liquid culture medium increased the dissolved-O2 partial pressure in direct proportion to the volume injected. The effect of hydrogen peroxide on the growth of subcultured clinical isolates of Candida albicans, Cryptococcus neoformans, Torulopsis glabrata, and other yeasts and on the growth of blood culture isolates of representative pathogenic bacteria was compared with its effect on their growth in vented and unvented stationary bottles. C. albicans and C. neoformans grew significantly better in bottles to which hydrogen peroxide had been added than in vented or unvented bottles. The advantage of hydrogen peroxide over venting was most marked with several slowly growing strains. Similar results were obtained in shaker cultures with strains of C. albicans which were inoculated directly from positive blood cultures. The effect of hydrogen peroxide tended to diminish during serial passage. T. glabrata grew less well when hydrogen peroxide was added, perhaps because of the absence of oxidase. The growth of Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis was not significantly inhibited or augmented by the addition of hydrogen peroxide. The growth of Escherichia coli was inhibited slightly. The value of the addition of hydrogen peroxide to blood cultures to improve the isolation of yeasts needs to be established by a clinical trial which would compare this method with established methods.