Antimicrobial Protein Produced by Vaginal Lactobacillus acidophilus that inhibits Gardnerella vaginalis

OBJECTIVE To isolate bacteriocin from a vaginal strain of Lactobacillus acidophilus. METHODS L. acidophilus 160 was grown on two media. The first was MRS broth for 18 hours; the cells were harvested, washed, and placed into a chemically defined medium. The second medium resembled vaginal fluid minus protein. Bacteriocin was precipitated from both media using ammonium sulfate. The growth-inhibiting activity of bacteriocin was determined by a bioassay using nine different isolates of Gardnerella vaginalis. RESULTS MRS broth is not a suitable medium for extracting bacteriocin, because it binds with Tween 80. Bacteriocin was isolated, without contaminating constituents, from chemically defined medium and identified as a single band by electrophoresis. Bacteriocin has a molecular weight of 3.8 kDa. All nine isolates of Gardnerella were inhibited by the bacteriocin isolated from L. acidophilus 160. CONCLUSIONS Bacteriocin produced by L. acidophilus 160 was isolated from the chemically defined medium (starvation medium) in a partially pure form. L. acidophilus 160 bacteriocin inhibited growth of all nine isolates of Gardnerella vaginalis.