In vitro investigation of probiotics' antimicrobial effects on bacteria that cause uterine infections in cattle.

Treating uterine infections in cattle is a challenge for farmers and veterinarians. Postpartum is the primary time for uterine infections, such as endometritis and metritis. They decrease fertility, have an impact on reproductive health, and lead to significant economic losses. The genital microbiota represents an opportunistic field of study in the area of cattle fertility. However, intravaginal antibiotic treatment affects the genital microbiome, leading to dysbiosis. Consequently, the modulation of this vaginal microbiome can be an effective alternative to antibiotics.

This study aims to to explore the potential use of bacteria as natural probiotics for the prevention of uterine infections and the improvement of reproductive health in dairy cows.

Seven Montbeliarade dairy cows were involved in this study: one with endometritis, one with metritis, and five healthy heifers. Various culture mediums were used to seed vaginal swab samples. The antibacterial activity of lactic acid bacteria against the infectious agents was investigated using two methods. Eight antibiotics were tested against the infectious agents using the MH diffusion method, and the results were recorded in an antibiogram.

Using phenotypic identification, Salmonella (E1), E. coli (E2), and Lactobacillus (E3, E4) from the vagina of healthy cows and a mixture of commercial probiotic L.plantarum and P.acidilactici (E5) were obtained. E4 and E5 exhibited moderate antimicrobial activity against E. coli, but none against Salmonella. E5 (4 mm) was tested by the overlay method against E. coli. Isolate E4 also exhibited moderate activity (2 mm). E. coli was found to be very sensitive to several antibiotics, particularly to aztreonam (32 mm) and gentamicin (28 mm), while Salmonella showed partial resistance.

These results underline the importance of characterizing probiotic strains prior to their application. Lactic acid bacteria have the potential to be probiotics, and more in vitro and in vivo studies are necessary to confirm the stability, safety, and efficacy of the strains in clinical settings.