Effect of antibiotics in semen extenders on the inseminated female

Exposure of bacteria to even small amounts of antibiotics can lead to the development of antimicrobial resistance. It is not known whether the widespread use of antibiotics in semen extenders could lead to antimicrobial resistance in the bacteria of the reproductive tract in horses and pigs. In both of these species, the volume of the insemination dose is relatively large (tens of mL) compared to the cow (0.25 mL), and the exposure to antibiotics is therefore greater.

The flora of the reproductive tract (cervix and vagina) of pigs and horses, respectively, will be swabbed before insemination, and at various time points afterwards. Changes in the resistance patterns of the isolated bacteria before and after insemination will be determined. Bacteria will be identified by MALDI-TOF; whole genome sequencing will be used to establish if the isolates are from the same bacterial strain.

In addition, factors likely to affect the appearance of bacteria in stallion semen will be investigated. Semen samples will be taken from stallions in different countries with different climates (Portugal, Germany and Sweden) to determine the effect of environmental conditions on bacterial content of semen. The microbiome will be determined by 16 S sequencing.

Hypothesis

The hypothesis is that exposure to antibiotics in semen extenders causes a change in the antimicrobial resistance patterns of the flora of the reproductive tract in inseminated females.

Relevance

Adding antibiotics to semen extenders is considered to be essential to inhibit the growth of bacteria in semen. However, the effect on the flora of the female reproductive tract has not been studied. Antimicrobial resistance is increasingly being reported in brood mares under investigation for fertility problems but it is not known whether this represents a real increase in occurrence or just that it is being investigated more often. Knowledge about the potential effects of antibiotics on the flora of the reproductive tract could help to promote the development of alternative (non-antibiotic) methods for inhibiting bacterial growth in semen extenders.