Research on new antimicrobial agents is needed, as more and more microorganisms that cause antibiotic-resistant diseases are emerging commercially. In this group, we can find strains of Staphylococcus aureus and Escherichia coli, which are highly opportunistic species. Faced with this perspective, research using essential oils present in plants is emerging as a therapeutic alternative for the treatment of antimicrobial infections. Many of these oils have, in their composition, monoterpene α-pinene, that shows to have antibacterial activity. The purpose of this research is to evaluate the antimicrobial activity of the positive enantiomer of α-pinene against strains of Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922. The methodologies used were: Disc-diffusion test, broth microdilution and bacterial death kinetics, all of which were standardized by CLSI. As a result, inhibition halos of 11 mm was obtained for the gram-positive strain and 12 mm for the gram-negative strain, both at the same concentration, 160 µl / ml. In addition, it was possible to observe with the death curve that the concentrations (1.25 µl/mL and 2.5 µl/mL of the (+)-α-pinene were able to eliminate the formation of bacterial colonies at one time of exposure of 2 hours for the E. coli strain. However, the death curve of the S. aureus strain was characterized by non-elimination of bacterial colonies at a 24 hours exposure time used for the experiment. Only amikacin evidenced its bacterial killing rate of all colonies within two hours of exposure. At the end, it was possible to verify the activity of the phytoconstituent against Escherichia coli strains ATCC 25922 and Staphylococcus aureus ATCC 25923, recommending the continuity of the studies with the use of different methodologies so that (+) - α-pinene in the future can be a compound used in antimicrobial therapy.

Background: The increasing and inappropriate use of antibiotics has increased the number of multidrug-resistant microorganisms to these drugs, causing the emergence of infections that are difficult to control and manage by health professionals. As an alternative to combat these pathogens, some monoterpenes have harmful effects on the bacterial cell membrane, showing themselves as an alternative in combating microorganisms. Therefore, the positive enantiomer α-pinene becomes an alternative to fight bacteria, since it was able to inhibit the growth of the species Escherichia coli ATCC 25922, demonstrating the possibility of its use as an isolated antimicrobial or associated with other drugs. Aims: The aim of this study is to evaluate the sensitivity profile of E. coli ATCC 25922 strain against clinical antimicrobials associated with (+) -α-pinene and how it behaves after successive exposures to subinhibitory concentrations of the phytochemicals. Methods: The minimum inhibitory concentration (MIC) was determined using the microdilution method. The study of the modulating effect of (+) -α-pinene on the activity of antibiotics for clinical use in strains of E. coli and the analysis of the strain's adaptation to the monoterpene were test using the adapted disk-diffusion method. Results: The results demonstrate that the association of monoterpene with the antimicrobials ceftazidime, amoxicillin, cefepime, cefoxitin and amikacin is positive, since it leads to the potentiation of the antibiotic effect of these compounds. It was observed that the monoterpene was able to induce cross-resistance only for antimicrobials: cefuroxime, ceftazidime, cefepime and chloramphenicol. Conclusion: It is necessary to obtain more concrete data for the safe use of these combinations, paying attention to the existence of some type of existing toxicity reaction related to the herbal medicine and to understand the resistance mechanisms acquired by the microorganism.

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The growing number of resistant bacteria is considered a worldwide public health problem. In this context, several control initiatives have been proposed, such as the elaboration of medicines from vegetable raw material as an alternative to fight against microorganisms such as Escherichia coli, which is related to approximately 50% of hospital infections. α-Pinene is found in the oils of many coniferous tree species and has antimicrobial activity against some microorganisms. The positive enantiomer of this compound (+)-α-pinene (+ AP), also called 4,6,6trimethylbicyclo [3.1.1] hept-3-ene, obtained from the company Sigma-Aldrich do Brasil Ltda. The solutions were dissolved in 1% Tween 80 and 5% DMSO and sterile distilled water was used to achieve desired concentrations. The tests were performed on the Escherichia coli strain ATTC 25922. To perform the modulation and adaptation tests, discs containing commercial antibiotics (ATM) were used. The modulating action of monoterpene was determined by the disc diffusion method. The antimicrobials Ceftazidime, Amoxicillin, Cefepime and Cefoxitin demonstrated synergism through association with phytoconstituent. For the remaining ATM, there was no statistically significant difference, and the effect of the association was classified as indifferent. It is concluded that

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