Preliminary characterization of inhibitors of Neisseria gonorrhoeae produced in vitro by Eubacterium limosum
Among anaerobic bacteria normally found in the urogenital flora, Eubacterium limosum was found to inhibit the in vitro growth of Neisseria gonorrhoeae. The antigonococcal activity produced by E. limosum was soluble in methanol and in a chloroform–methanol mixture (30:70). The fraction soluble in chloroform–methanol (30:70) yielded eight absorbance peaks when chromatographed on Bio-Gel P-2 and the inhibitory activity was found in the first two peaks. This activity was not adsorbed on DEAE Sephacel and was eluted with distilled water in a peak considered as peak 1, on which preliminary characterization was done. The inhibitory activity of peak 1 was found to be heat and pH resistant and not susceptible to proteases, lipase, or amylases. When peak 1 was chromatographed on cellulose paper using a butanol – acetic acid (4:1) solvent system, eight different spots were detected upon spraying the paper with ninhydrin. No spot was detected with anthrone, bromothymol, nor Sudan black reagents used for the detection of carbohydrates and lipids. Based on sodium dodecyl sulfate – urea polyacrylamide gel electrophoresis and gel chromatography on Sephadex G-25, peak 1 appeared either as a diffuse band and as a single peak, respectively. The molecular weight of the inhibitory complex was estimated to be 2400. All these results suggest that the antigonococcal activity produced by E. limosum is composed of more than one low molecular weight amino compound.