Pilot Study on the Action of Thymus vulgaris Essential Oil in Treating the Most Common Bacterial Contaminants and Salmonella enterica subsp. enterica Serovar Derby in Poultry Litter.

The indiscriminate use of antimicrobials in poultry farms is linked to the increase in multi-resistant bacteria. Accordingly, based on the antimicrobial properties of Thyme Essential Oil (TEO), the present study evaluated the effects of TEO on the reduction of common microbial contaminants and Salmonella on poultry litter. A litter bulk sample was collected in a broiler farm and qualitative/quantitative investigations identified Escherichia coli and Mammaliicoccus lentus. The experimental contamination with Salmonella Derby wild strain was also performed. All pathogens showed phenotypic and genotypic resistance to different classes of antibiotics. The litter, split in different units, was treated with aqueous solutions of TEO at different concentrations (5% to 1.25%), demonstrating its effectiveness in reducing the total number of bacteria. The strongest antibacterial action was observed at the lowest concentration against Enterobacteriaceae, with a growth reduction compared to the positive control of 73.3% and 77.8% against E. coli and Salmonella Derby, respectively, while towards M. lentus the reduction was 50%. Our data confirm the antimicrobial activity of TEO and suggest its possible application for the treatment of poultry litter as an effective and natural approach for the prevention of diseases caused by the most common bacteria that colonize poultry farms, counteracting the onset of antibiotic resistance.

Long-term immunogenicity and protection against Mycoplasma agalactiae induced by an oil adjuvant vaccine in sheep.

The long-term protective immunity of an inactivated mineral-oil adjuvanted Mycoplasma agalactiae vaccine was evaluated in sheep. The antigen suspension was emulsified with a mixture of three mineral oils (Montanide ISA-563, Marcol-52, Montane-80 at the ratio of 30%, 63%, and 7%, respectively). Twenty-two animals were divided in 2 groups (A and B) and immunised with two doses of the vaccine (group A, n=14) or used as unvaccinated control (group B, n=8). Five months after the second vaccination, seven animals of group A and four animals of group B were challenged by nasal route with M. agalactiae. The remaining seven vaccinated and four control animals were challenged intranasally eight months after vaccination. The vaccine was able to induce a full-protective immunity preventing the clinical signs of contagious agalactia and the infection by M. agalactiae in all groups of animals irrespective of the time of challenge after booster administration.

An oil-emulsion vaccine induces full-protection against Mycoplasma agalactiae infection in sheep.

The immunogenicity and efficacy of three inactivated vaccines (A, B, C) prepared with Mycoplasma agalactiae (M. agalactiae) and with different oil-emulsion adjuvants were evaluated in sheep. Twenty-eight animals were used, divided into four groups (a, b, c, d) of seven animals each. Three groups were immunized with the same vaccine, but using different adjuvants, while one group (d) was used as an unvaccinated control group. All the vaccine formulations were able to induce clinical protection of animals after challenge with M. agalactiae, but only vaccine C, emulsioned with Montanide ISA-563, Marcol-52 and Montane-80 (ratio: 30%, 63%, 7% respectively), was able to induce full protection in challenged animals, preventing both the onset of clinical signs and infection by M. agalactiae.