Study of boar sperm interaction with Escherichia coli and Clostridium perfringens in refrigerated semen

The present study analyses the interaction of boar spermatozoa with Escherichia coli and Clostridium perfringens, in 9-day refrigerated semen samples. Ejaculates from 10 sexually mature boars were inoculated with either E. coli or C. perfringens, at infective titer from 101 to 107 CFU/mL. The sperm-bacteria interaction was evaluated by optical and scanning electron microscopy (SEM), through: a) determining the proportion of spermatozoa with either E. coli or C. perfringens adhered and the number and localization of bacteria adhered on the sperm surface; and b) analyzing the effects of bacterial contamination on sperm membrane integrity. While proportions of spermatozoa with bacteria adhered did not differ between E. coli and C. perfringens during the first 3 days of storage, proportions of spermatozoa with E. coli adhered were greater than those with C. perfringens on and subsequent to Day 4 of storage. Both bacterial types adhered non-specifically over the sperm surface; nevertheless, the proportion of spermatozoa with bacteria adhered to the mid-piece was greater with E. coli infection, and of spermatozoa with bacteria adhered to the principal piece greater with C. perfringens infections. Alterations in the sperm plasma membrane induced by C. perfringens affected the acrosomal end and appeared at Day 4 of storage, those induced by E. coli were apparent from Day 7 of storage and affected the acrosomal region and mid-piece. In conclusion, E. coli has a greater capacity to adhere to the sperm surface than C. perfringens during liquid storage at 17 °C, but damage on sperm membrane integrity induced by C. perfringens occurred in a shorter period of time.