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  Discussion on Reseach Summary: Gentamicin use in semen extenders questioned
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DrO

Posted on Tuesday, Jun 5, 2007 - 12:31 pm:

Here is a study that flies in the face of a common practice of adding antibiotics to semen extenders, specifically gentamycin. The study found that while the antibiotic decreased semen motility it did not reduce the negative effects of the bacteria. Are we making a mistake routinely adding antibiotics to the extender? At the very least I would consider changing to other choices, perhaps one of the wide spectrum penicillins?
DrO

Theriogenology. 2007 Mar 15;67(5):912-8. Epub 2006 Dec 1.
Influence of bacteria and gentamicin on cooled-stored stallion spermatozoa.

Aurich C, Spergser J.

Centre for Artificial Insemination and Embryo Transfer, Department of Animal Breeding and Reproduction, University for Veterinar y Sciences, Veterinarplatz 1, 1210 Vienna, Austria. christine.aurich@vu-wien.ac.at

This study investigated effects of bacteria from the genital tract of horses and the effect of gentamicin in semen extender on spermatozoal function in cooled-stored stallion semen. Semen was collected from healthy stallions and processed with a milk-based extender with or without gentamicin (1g/l). Pseudomonas (Ps.) aeruginosa, Staphylococcus (St.) aureus, Streptococcus (Sc.) equi subsp. equi (Sc. equi), Sc. equi subsp. zooepidemicus (Sc. zooepidemicus), Sc. dysgalactiae subsp. equisimilis (Sc. equisimilis) or culture medium alone (control) were added. Immediately after addition of bacteria and after storage at 5 degrees C for 24, 48 and 72h, motility, velocity and membrane integrity of diluted semen were determined with a CASA system. After 24h, semen with Ps. aeruginosa and Sc. equisimilis showed significantly lower motility and velocity compared to all other groups; after 72h these differences still existed for Ps. aeruginosa (p<0.05). The percentage of membrane-intact spermatozoa was significantly lower after 24h of storage in spermatozoa incubated with Sc. equisimilis and after 72h with Sc. equisimilis and Ps. aeruginosa. Addition of gentamicin to extender resulted in decreased motility and velocity in semen without addition of bacteria and did not improve motility parameters in semen with bacteria added. In conclusion, certain bacteria may have detrimental effects on semen quality during cooled-storage. These effects are not reduced by addition of gentamicin. Gentamicin can negatively affect spermatozoal function in extended semen during cooled-storage and therefore, optimal concentrations have to be tested for the respective extender medium.
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