Antifungal Effect of Hydrogen Peroxide on Catalase-Producing Strains of Candida spp.

Bryan Larsen,Sandra White

doi:10.1155/s1064744995000354

Abstract

Objective: Clinical isolates of Candida were tested for the presence of catalase and susceptibility to hydrogen peroxide. Methods: MIC was tested by broth dilution technique and catalase was determined by a spectrophotometric procedure. Results: All 38 strains tested were inhibited by hydrogen peroxide in concentrations ranging from 4.4 to 88 mM/l, with non-albicans isolates generally requiring higher concentrations of hydrogen peroxide for inhibition. Growth media consisting of glucose and protein diminished the antifungal effectiveness of hydrogen peroxide, as did the presence of hemoglobin, in incubation mixtures. However, hydrogen peroxide exerted greater inhibition at pH 4 than at pH 7. Although all Candida isolates tested possessed catalase, there was no apparent correlation between the catalase activity of individual isolates and the minimal antifungal concentration of hydrogen peroxide. Conclusions: This study suggested that, despite the production of catalase by vaginal microorganisms, hydrogen peroxide may exert a regulating influence which may be further modified by the proteins found in the vaginal milieu.

Highlights

All 38 strains tested were inhibited by hydrogen peroxide in concentrations ranging from 4.4 to 88 mM/l, with non-albicans isolates generally requiring higher concentrations of hydrogen peroxide for inhibition
This study suggested that, despite the production of catalase by vaginal microorganisms, hydrogen peroxide may exert a regulating influence which may be further modified by the proteins found in the vaginal milieu. (C) 1995 Wiley-Liss, Inc
KEY WORDS Normal vaginal flora, vaginal bacteria, lactobacilli or many years, lactobacilli have been considered to be an important part of the vaginal microbial ecosystem, often credited with maintaining vaginal health by inhibiting other microbial species

Summary

Methods

MIC was tested by broth dilution technique and catalase was determined by a spectrophotometric procedure. The specimens were plated on BIGGY (BBL, Cockeysville, MD) agar lz and returned to the laboratory. Candida isolates from these vaginal specimens were preliminarily identified by brown colonies on the BIGGY agar. The ability of each isolate to produce germ tubes was tested in human serum. Germ tubes were produced by 26 strains and were presumptively considered to be C. albicans or C. stellatoidia; the remaining 12 were described as non-albicans Candida. All isolates were preserved and propagated by weekly subculture on Sabouraud’s agar. All fungal strains in the culture collection showed catalase activity evidenced by the generation of bubbles when a colony from a Sabouraud’s agar plate was placed in a drop of 3 % hydrogen peroxide (certified 3 %, Fisher, Fairlawn, NJ)

Results

Discussion

Conclusion