Testosterone and estradiol modify the expression of adhesins and biofilm formation in Actinobacillus seminis.

Actinobacillus seminis is the causal agent of epididymitis and has other effects on the reproductive tracts of small ruminants and bovines. This bacterium causes infection when luteinizing (LH) or follicle-stimulating hormones increase, and hosts reach sexual maturity. LH induces female ovulation and male testosterone production, suggesting that these hormones affect A. seminis pathogenicity. In the present study, we evaluated the effect of testosterone (1-5 ng/ml) or estradiol (5-25 pg/ml) added to culture medium on the in vitro growth, biofilm production, and adhesin expression of A. seminis. Estradiol does not promote the growth of this bacterium, whereas testosterone increased A. seminis planktonic growth 2-fold. Both hormones induced the expression of the elongation factor thermo unstable (EF-Tu) and phosphoglycerate mutase (PGM), proteins that A. seminis uses as adhesins. Estradiol (5 or 10 pg/ml) decreased biofilm formation by 32%, whereas testosterone, even at 5 ng/ml, showed no effect. Both hormones modified the concentrations of carbohydrates and eDNA in biofilms by 50%. Amyloid proteins are characterized by their capacity to bind Congo red (CR) dye. Actinobacillus seminis binds CR dye, and this binding increases in the presence of 5-20 pg/ml estradiol or 4 ng/ml testosterone. The A. seminis EF-Tu protein was identified as amyloid-like protein (ALP). The effect of sexual hormones on the growth and expression of virulence factors of A. seminis seems to be relevant for its colonization and permanence in the host.

Microbiological, molecular, and histopathological findings in goats experimentally infected with Actinobacillus seminis.

The objective of this study was to experimentally evaluate the pathogenicity of an Actinobacillus seminis isolate named SAAS01 in goats. Animals were challenged with 2 mL of a suspension containing 1,5 × 108 CFU/mL of A. seminis (SAAS01 isolate) through the intrapreputial, epididymis tail, and conjunctival routes. Epididymis and testicular fragments were submitted to histopathological exam, and semen samples underwent microbiological and molecular diagnoses. Clinically, a unilateral increase in firm consistency was observed in the epididymis and testicles of two animals inoculated in epididymis tail and in one animal inoculated through conjunctival sac; this firmness continued until the day of euthanasia. Two goats inoculated through epididymis tail and conjunctival sac routes presented histopathological findings with macroscopically and microscopically significant changes. A. seminis was isolated from semen samples collected from goats inoculated through the epididymis tail and conjunctival sac routes. A. seminis DNA was amplified from six semen samples of three goats inoculated through the epididymis tail, two in conjunctival sac and one through intrapreputial route. The experimental infection model using goats confirmed the pathogenicity of the A. seminis isolate, demonstrating the predilection of the agent for the epididymis, with clinical signs, histopathological lesions, bacterial isolation, and a positive molecular diagnosis.

Isolation of Actinobacillus seminis from a goat with clinical epididymo-orchitis in Brazil.

The present study reports the first isolation of Actinobacillus seminis from a goat in Brazil. A four-year-old Moxotó breeding goat in a flock of 70 goats and 65 sheep reared together in the county of Patos, semiarid region of Northeastern Brazil, showed clinical signs of unilateral orchitis and epididymitis. Diagnosis of A. seminis infection was confirmed by association of clinical findings, bacterial isolation and 16S rRNA gene sequencing. This result suggests that A. seminis may be an additional cause of infertility in goats, and that sheep may be the source of infection because the mixed farming system allows the contact between sheep and goats in the semiarid region of Northeastern Brazil.

Isolation of Actinobacillus seminis from a goat with clinical epididymo-orchitis in Brazil

The present study reports the first isolation of Actinobacillus seminis from a goat in Brazil. A four-year-old Moxotó breeding goat in a flock of 70 goats and 65 sheep reared together in the county of Patos, semiarid region of Northeastern Brazil, showed clinical signs of unilateral orchitis and epididymitis. Diagnosis of A. seminis infection was confirmed by association of clinical findings, bacterial isolation and 16S rRNA gene sequencing. This result suggests that A. seminis may be an additional cause of infertility in goats, and that sheep may be the source of infection because the mixed farming system allows the contact between sheep and goats in the semiarid region of Northeastern Brazil.