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Antibiotics have been used for decades in poultry diets to increase performance and decrease morbidity and mortality. The growing concern over the spreading of antibiotic-resistant bacteria among animals and humans has resulted in the ban of the feed use of antibiotic growth promoters in livestock and in some cases additives derived from plants are used as alternative. Four commercial essential oils, from litsea (Litsea cubeba (Lour.) Pers.), oregano (Origanum vulgare L. subsp. hirtum), marjoram (Origanum majorana L.), thymus (Thymus vulgaris L.) and their mixtures, were tested against pathogenic bacteria and yeasts that may be shed in faeces by poultry. In particular, the analysis were carried out against reference and wild bacterial strains of Salmonella enterica serovar Typhimurium, Yersinia enterocolitica, Listeria monocytogenes, Enterococcus durans, E. faecalis, and E. faecium, and wild isolates of Candida albicans, C. tropicalis, C. guilliermondii, C. krusei, C. parapsilosis and Saccharomyces cerevisiae. Essential oils had varying degrees of growth inhibition in relationship to the tested bacterial and yeast strains; however the best results were achieved by O. vulgare and T. vulgaris. All mixtures gave good results with reference and field bacterial strains, with MIC values ranging from 1.13 to 0.14 mg/ml. The mixture composed by O. vulgare, T. vulgaris and O. majorana appeared the most effective against the tested yeast isolates, with MIC 1.85 mg/ml. O. vulgare and T. vulgaris showed good antimicrobial activities, thus they seem useful not only to promote poultry growth, but also to control fastidious microorganisms commonly occurring in digestive tract of these animals.

Thymus serpyllum was assayed against clinical animal isolates of Microsporum canis, Trichophyton mentagrophytes, T. erinacei, T. terrestre and Microsporum gypseum, main causative agents of zoonotic and/or environmental dermatophytoses in humans. Single main components present in high amounts in such EOs were also tested. Different dermatophyte species showed remarkable differences in sensitivity. In general, more effective EOs were T. serpyllum (MIC range 0.025%-0.25%), O. vulgare (MIC range 0.025%-0.5%) and L. cubeba (MIC range 0.025%-1.5%). F. vulgare showed a moderate efficacy against geophilic species such as M. gypseum and T. terrestre. Among single main components tested, neral was the most active (MIC and MFC values ≤ 0.25%). The results of the present study seem to be promising for an in vivo use of some assayed EOs.

Helichrysum genus consists of about 600 species widespread throughout the world, especially in South Africa and in the Mediterranean area. In this study the aroma profile (HS-SPME) and the EO compositions of seven Helichrysum species (H. cymosum, H. odoratissimum, H. petiolare, H. fontanesii, H. saxatile, H. sanguineum, and H. tenax) were evaluated. All the plants were grown in Italy under the same growth conditions. The volatile constituents, particularly monoterpenes, depended by the plant's genotype and ecological adaptation. This study represents the first headspace evaluation on the selected plants and the results evidenced that monoterpenes represented the main class of constituents in five of the seven species analysed (from 59.2% to 95.0%). The higher content in sesquiterpene hydrocarbons was observed in the Mediterranean species of H. sanguineum (68.0%). Only H. saxatile showed relative similar abundance of monoterpenes and sesquiterpene hydrocarbons. The essential oil composition of the majority of examined species are characterised by high percentage of sesquiterpenes (especially β-caryophyllene and δ-cadinene) ranging from 51.3% to 92.0%, except for H. cymosum, H. tenax, and H. sanguineum leaves where monoterpenes predominated (from 51.7% to 74.7%).