The aim of this study was to verify the existence of the synergistic antibacterial effect of lavender essential oil and linalool individually combined with the antibacterial drug gentamicin. We investigated in vitro the effectiveness of the combinations of gentamicin and lavender essential oil and of gentamicin and linalool against the following strains: Staphylococus aureus ATCC 25923, Staphylococus aureus MRSA and Pseudomonas aeruginosa ATCC 9027. In order to determine the sensitivity of these microorganisms, we determined the minimum inhibitory concentration (MIC – Minimal Inhibitory Concentration). The study of the interaction of gentamicin with lavender oil and linalool was evaluated by the checkerboard method. Synergistic interaction between lavender essential oil and gentamicin and between linalool and gentamicin was observed against Staphylococcus aureus ATCC 25923 and Staphylococcus aureus MRSA. In particular, a very strong synergistic interaction was observed against Staphyloccocus aureus MRSA (lavender essential oil FIC index = 0.14; linalool FIC index = 0.13). In contrast, combinations of gentamicin and lavender essential oil and of gentamicin and linalool were less effective against Pseudomonas aeruginosa growth.
Biological activity of lavender essential oil is a property that can potentially find an application in poultry nutrition. Nowadays, the use of bioactive compounds is encouraged in many areas of industry and agriculture, since these substances have similar properties as withdrawn antibiotic growth promoters. Additionally, antibiotic resistance bacteria are one of the most important current threats to animal health. The purpose of the study was to determine the influence of lavender essential oil on the production parameters and blood parameters in broiler chickens and to assess the lavender oil’s in vitro reaction in a combination with enrofloxacin towards Escherichia coli. One-day-old non-sexed chicks (Ross 308) were divided into three experimental groups, each consisting of 100 individuals (five replicate of 20 boiler chicken each). The chickens in the control group received drinking water with no addition of lavender essential oil. In the experimental groups, lavender oil was added to the drinking water at a concentration of 0.4 mL/L, in the LEO1–42 from 1 to 42 days of age and the LEO22–42 group from the 22 to 42 days of age. The chickens’ body weight, feed consumption, water consumption, deaths and elimination due to health reasons were determined in the experiment. On day 42 of the chickens’ lives, blood samples were collected based on which selected parameters were identified. An in vitro experiment of lavender oil in combination with enrofloxacin was investigated with a checkerboard method. The results of the experiment showed the antimicrobial and antioxidant activity of lavender essential oil and its positive effect on the production results of broiler chickens. The study results proved that the addition of lavender oil positively impacted the chickens’ final body weight and feed conversion ratio (p < 0.01). No differences were observed between the groups for water consumption, death rate and the examined biochemical and immunological blood serum indices. Lavender essential oil was demonstrated to increase the blood serum’s total antioxidant status. A synergistic reaction in vitro was observed for lavender oil combined with enrofloxacin against resistant strains of Escherichia coli. Based on our study, a health-promoting effect of adding LEO to water for broiler chickens was found. Moreover, in vitro studies indicate a significant effect of lavender essential oil on the inhibition of the resistant strains of Escherichia coli growth and synergistic reaction with enrofloxacin.
Staphylococcus pseudintermedius is considered as a major pathogen in dogs, typically involved in skin and ear infections. Other staphylococci, as well as ß-hemolytic streptococci, Pseudomonas aeruginosa or yeast-like fungi of the genus Malassezia also play an important role in inflammation. Because of this diversity, an appropriate choice of antimicrobial agent(-s) can be difficult. A total of 474 tests were performed (including 255 pyoderma and 219 otitis externa cases). In the case of pyoderma, 82.4% of skin lesions were caused by stap hylococci. Co-infections with ß-hemolytic streptococci (17.3 %), Malassezia sp. (15.7 %) and P. aeruginosa (4.3 %) were also recorded. For external ear infections, the share of staphylococci in inflammation was lower (44.8 %) than that of Malassezia sp. (58 %). Relatively frequent co-infections with ß-hemolytic streptococci (18.8 %) and P. aeruginosa (7.8 %) were also noted. A total of 308 susceptibility tests for coagulase-positive staphylococci were performed (210 and 98 for skin and otitis externa, respectively). In ≥ 86 % of cases, amoxicillin potentiated with clavulanic acid, cephalexin and fluoroquinolones effectively inhibited the growth of all bacteria in vitro. A total of 25 isolates (24 S. pseudintermedius and one S. aureus) were considered as methicillin-resistant. The mecA gene was identified in 100 % of those strains but only 44 % of the isolates additionally carried the blaZ gene. All mecA-positive staphylococci were multidrugresistant, mainly to all ß-lactams, fluoroquinolones, linkozamides, macrolides as well as sulfonamides but always susceptible to mupirocin. Overall, multidrug-resistance varied between 6 % (otitis externa) and 9 % (inflamed skin) and may become a significant problem in the future.
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