Essential oils of Eugenia spp. (myrtaceae) show in vitro antibacterial activity against Staphylococcus aureus isolates from bovine mastitis.

Bovine mastitis, an inflammation of the mammary glands, is mainly caused by bacteria such as Staphylococcus aureus. While antibiotics are the primary treatment for this disease, their effectiveness is often diminished due to resistant strains and biofilm formation, creating the need for safer and more efficient therapies. Plant-based oil therapies, particularly those derived from the genus Eugenia, are gaining popularity due to their pharmacological potential and historical use. In this study, we evaluated the antibacterial, antibiofilm, and synergistic potential of essential oils (EOs) from four species of the genus Eugenia (E. brejoensis, E. gracillima, E. pohliana, and E. stictopetala) against S. aureus isolates from bovine mastitis. The EO of E. stictopetala was obtained by hydrodistillation, and its composition was analyzed using gas chromatography coupled with mass spectrometry. The experiment employed seven clinical isolates from mastitis and two control strains: ATCC 33591 (methicillin-resistant S. aureus - MRSA) and ATCC 25923 (methicillin-susceptible and biofilm producer). A broth microdilution assay was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the EOs and oxacillin. The EO of E. stictopetala contained (E)-caryophyllene (18.01%), ß-pinene (8.84%), (E)-nerolidol (8.24%), and α-humulene (6.14%) as major compounds. In the MIC assay, all essential oils showed bactericidal and bacteriostatic effects, especially the species E. brejoensis and E. pohliana, which had MICs ranging from 64 to 256 µg/mL. Regarding the antibiofilm effect, all essential oils were capable of interfering with biofilm formation at subinhibitory concentrations of ½ and » of the MIC. However, they did not significantly affect pre-established biofilms. Additionally, a synergistic interaction was detected between the EOs and oxacillin, with a reduction of 75-93.75% in the antimicrobial MIC. Molecular docking studies indicated that the phytochemicals ß-(E)-caryophyllene, (E)-nerolidol, Δ-elemene, and α-cadinol present in the EOs formed more stable complexes with penicillin-binding proteins, indicating a possible mechanism of antibacterial action. Therefore, these results show that the essential oils of Eugenia spp. are promising sources for the development of new therapeutic methods, opening new perspectives for a more effective treatment of bovine mastitis.

Antimicrobial and antibiofilm activity of highly soluble polypyrrole against methicillin-resistant Staphylococcus aureus.

AIMS: The purpose was to evaluate the antimicrobial activity of highly soluble polypyrrole (Hs-PPy), alone or combined with oxacillin, as well as its antibiofilm potential against methicillin-resistant Staphylococcus aureus strains. Furthermore, the in silico inhibitory mechanism in efflux pumps was also investigated. METHODS AND RESULTS: Ten clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and two reference strains were used. Antimicrobial activity was determined by broth microdilution, and the combination effect with oxacillin was evaluated by the checkerboard assay. The biofilm formation capacity of MRSA and the interference of Hs-PPy were evaluated. The inhibitory action of Hs-PPy on the efflux pump was evaluated in silico through molecular docking. Hs-PPy showed activity against the isolates, with inhibitory action between 62.5 and 125 µg ml-1 and bactericidal action at 62.5 µg ml-1, as well as synergism in association with oxacillin. The isolates ranged from moderate to strong biofilm producers, and Hs-PPy interfered with the formation of this structure, but not with mature biofilm. There was no in silico interaction with the efflux protein EmrD, the closest homolog to NorA. CONCLUSIONS: Hs-PPy interferes with biofilm formation by MRSA, has synergistic potential, and is an efflux pump inhibitor.

Action of crude ethanol extract of Hymenaea martiana leaf, gallic acid, and polypyrrole (PPy) against Aeromonas hydrophila.

Pisciculture represents one of the industries with the fastest growth rates worldwide. However, it presents obstacles to its development, such as bacteriosis, which is conventionally treated with antibiotics. The indiscriminate and inappropriate use of antibiotics can lead to bacterial resistance, thus alternatives to the use of antibiotics have been researched. The study aimed to analyze the potential of crude ethanol extract (CEE) from Hymenaea martiana leaf, gallic acid (GA), and polypyrrole (PPy) against Aeromonas hydrophila. Tests were performed to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the compounds individually and in synergy (checkerboard) against A. hydrophila and in silico tests between the compounds evaluated. The CEE of H. martiana leaf and PPy were effective against A. hydrophila with MBC results of 3125 µg/mL for the CEE of H. martiana and 125 µg/mL for PPy. Evaluating the GA, a MIC and MBC of 125 µg/mL was obtained. In the interaction tests (checkerboard, using PPy/CEE and PPy/GA), there was a significant reduction in individual introductions. Thus, for the PPy/CEE tests, we had a reduction of MIC/MBC to 1.95 and 781.25 µg/mL, and for the synergy tests between PPy/GA to 7.8125 and 31.125 µg/mL, respectively. The synergy tests are encouraging, and it is possible to verify a decrease of up to 98% in the introduction of PPy, 75% in CEE for H. martiana and 75.1% for GA, when compared to their individual tests. The tests with GA are encouraging due to GA's effectiveness as an antimicrobial agent and high synergy with polypyrrole, both in vitro results and molecular docking experiments showed the actions at the same activation site in A. hydrophila. In vivo tests evaluating isolated components of CEE from H. martiana in synergy with PPy should be performed, to verify the quality of the interactions and the improvement of the immune responses of the animals. It was evidenced that gallic acid, a substance isolated from the extract, tends to have more promising results. This is relevant since the industry has been developing these compounds for different uses, thus providing easier access to the product. Thus, the present study indicates an efficient alternative in the use of bioactive compounds as substitutes for conventional antimicrobials.