The standard strain of Serratia marcescens causing sperm agglutination in vitro leading to infertility in female mice without causing inflammation was already available in the laboratory. So, to investigate the underlying mechanism and its role in infertility, the corresponding sperm agglutination factor was isolated. As only the washed cells, and not the supernatant, showed sperm agglutination so the washed cells were sonicated and the proteins in the supernatant were precipitated out with ammonium sulphate at the saturation of 60-80% and purified by gel permeation chromatography followed by ion exchange chromatography. The sperm agglutination factor (SAF) was found to be a ~54 kDa protein. SAF at a concentration of 60 μg was able to cause 100% agglutination of mouse spermatozoa within 30 min of incubation at 37°C, whereas a concentration of 80 μg resulted in instant loss of viability of mouse spermatozoa and major decrease in Mg++ ATPase activity was observed at a concentration of 100 µg. Further, in vivo studies demonstrated that a single intravaginal administration of SAF (10 μg) before mating completely prevented conception in female mice. Thus, SAF might be one of the reasons for female infertility and with its excellent spermicidal activity, it could be developed as a potent vaginal contraceptive in future.
Prabha V Negi S, Chauhan A, Vander H, Rana K and Thaper D