Addition of lactic acid bacteria to diluted ram semen as vehicle for vaginal inoculation: interaction with seminal microbiota, sperm quality and antibacterial in vitro effect against Mycoplasma agalactiae.

Abstract

BACKGROUND: The use of lactic acid bacteria (LAB) as a probiotic in seminal doses of small ruminants has been suggested due to its antibacterial effects against pathogens such as Mycoplasma agalactiae (Ma) and positive effects on ovine vaginal health. The present in vitro study evaluates the antibacterial effect against Ma of a wild LAB strain from caprine prepuce and a commercial human probiotic (L3) composed by Lactobacillus spp., and evaluates their impact on sperm quality, DNA fragmentation, and the bacterial community composition in the studied conditions. One preputial wild strain (P65) and L3 were tested to assess its antibacterial in vitro potential against Ma in semen doses. RESULTS: In experimental conditions with diluted ram semen, the strain P65, identified as Enterococcus hirae, significantly reduced Ma concentration from 7.202 to 0.000 log CFU/mL (p&#x2009;<&#x2009;0.05), and L3 from 6.872 to 2.699 log CFU/mL (p&#x2009;<&#x2009;0.001). In addition, experimental condition with P65 suffered a greater Ma inhibition and pH reduction over 15&#xa0;h of incubation (p&#x2009;<&#x2009;0.05). In experimental conditions with LAB, sperm motility exceeded 75% in the presence of Ma, with no adverse effects on DNA fragmentation observed. A negative effect on Ma was also observed in diluted semen from rams, which could be attributed to the predominance of several species of Lactobacillus spp. in the semen diluted without antibiotics. Metabarcoding analyse evidence that Actinobacillus, Lactobacillus, and Staphylococcus were naturally present in the diluted semen studied. Moreover, under conditions with diluted semen and the wild strain P65, no significant increase in opportunistic pathogens as Escherichia-Shigella was observed. CONCLUSIONS: This study is the first in vitro report of the antibacterial potential of male reproductive tract LAB against Ma and suggests its ecological importance in the reproductive microbiota of small ruminants. The replacement of antibiotics with species-specific LAB in seminal doses of small ruminants should be evaluated in future in vivo studies.