Effects of different concentrations of enterotoxigenic and verotoxigenic E. coli on boar sperm quality

The presence of bacteria in boar semen causes economic losses in artificial insemination (AI) centers, as a consequence of alterations on boar sperm quality. For this reason, the effects of different concentrations of enterotoxigenic Escherichia coli (ETEC) and verotoxigenic E. coli (VTEC) on boar sperm quality were determined in this study, by conducting two experiments. The first one consisted of assessing these effects on boar sperm quality after incubating the inoculated doses at 37 °C for a 96-h period, whereas the second inoculated doses were stored at 15 °C during 11 days. In both experiments, the infective concentrations ranged from 108 cfu mL−1 to 102 cfu mL−1; the negative control being a non-inoculated dose. Twenty-four hours after inoculation, we checked by PCR for the presence of bacteria in all tubes. Sperm quality (sperm motility, sperm viability and sperm morphology) was assessed at 24 h, 48 h, 72 h and 96 h after inoculations in the first experiment (37 °C), and after 3, 5, 7, 9 and 11 days in the second (15 °C). Whereas no changes were observed in sperm morphology in both experiments, the percentages of progressive motile spermatozoa dramatically diminished after 24 h of incubation at 37 °C, the effect being more detrimental at the highest infective concentration of microbes. Moreover, a significant decrease in the percentage of viable spermatozoa in the tube inoculated with the highest concentration (108 cfu mL−1) was detected after 24 h of incubating contaminated doses at 37 °C. After 48 h of incubation, the presence of infective concentrations of ETEC and VTEC from 108 cfu mL−1 to 103 cfu mL−1 resulted in a significant diminution in the percentage of viable spermatozoa.These results suggest that ETEC and VTEC PCR analyses should be done in doses destined for AI to minimize the use of doses with diminished sperm quality due to the presence of bacteria and to avoid the potential spread of infective diseases.