Abstract :Various studies have shown Pseudomonas aeruginosa to be one of the most prevalent organisms
involved in causing infertility in males and females. To explore the possible mechanism underlying
this process, standard strain of Pseudomonas aeruginosa (MTCC 3542) was employed and it was
found to cause complete immobilization of mouse spermatozoa in vitro. Further, only cell-free
supernatant showed immobilization activity, indicating that the sperm immobilization factor might
be released extracellular by the organism, as no activity was observed with the washed cells. This
bioactive molecule from the supernatant was precipitated out with ammonium sulphate at the
saturation of 60% to 80% and purified by gel permeation chromatography followed by ion exchange
chromatography. The Sperm Immobilization Factor (SIF) was found to be a ~16 kDa protein. SIF
at a concentration of 50 µg was able to cause 100% immobilization of mouse spermatozoa within 30
min of incubation at 37ºC, whereas a concentration of 65 µg resulted in instant loss of viability of
mouse spermatozoa and a total loss of Mg++ ATPase activity was observed at a concentration of 100
µg. Further, in vivo studies showed that a single intravaginal application of SIF (10 µg) before mating
completely prevented conception in female mice. Also, no pregnancy related changes were observed
from histological examination in the reproductive organs (i.e. ovary and uterus) of female mice
receiving 10 µg of SIF in comparison to female mice receiving PBS. Thus, SIF with its spermicidal
activity could be developed as a potent vaginal contraceptive for future use.