In vitro Evaluation of Fungal Susceptibility and Inhibition of Virulence by Diosgenin.

Fungal infections are a public health problem that mainly affects immunosuppressed people, Candida spp. have been responsible for most sources of contamination and invasive fungal infections described around the world. The need arises to find new therapeutic approaches to combat growing infections. Plants and natural products have been considered a valuable source for discovering new molecules with active ingredients. Diosgenin is a sapogenin found in the families of Leguminosae and Dioscoreaceae, it is obtained mainly from the dioscin saponin through the hydrolysis method, it is a phytochemical that has been highlighted in the treatment of various diseases, as well as in combating microbial resistance. The present study aimed to evaluate the susceptibility of fungal strains to diosgenin, as well as verify the association with the reference drug and evaluate the inhibition of the virulence factor through morphological changes in the yeast state to the filamentous form of hyphae and pseudohyphae in strains of Candida albicans, Candida tropicalis and Candida krusei using the broth microdilution method and microculture technique. Antifungal assays revealed that diosgenin was not able to inhibit the growth of the tested strains. However, it was able to inhibit the fungal dimorphism of the strains evaluated, however further studies are recommended to verify its effectiveness against other virulence factors.

Comparative Antibacterial and Efflux Pump Inhibitory Activity of Isolated Nerolidol, Farnesol, and α-Bisabolol Sesquiterpenes and Their Liposomal Nanoformulations.

The efflux systems are considered important mechanisms of bacterial resistance due to their ability to extrude various antibiotics. Several naturally occurring compounds, such as sesquiterpenes, have demonstrated antibacterial activity and the ability to inhibit efflux pumps in resistant strains. Therefore, the objective of this research was to analyze the antibacterial and inhibitory activity of the efflux systems NorA, Tet(K), MsrA, and MepA by sesquiterpenes nerolidol, farnesol, and α-bisabolol, used either individually or in liposomal nanoformulation, against multi-resistant Staphylococcus aureus strains. The methodology consisted of in vitro testing of the ability of sesquiterpenes to reduce the Minimum Inhibitory Concentration (MIC) and enhance the action of antibiotics and ethidium bromide (EtBr) in broth microdilution assays. The following strains were used: S. aureus 1199B carrying the NorA efflux pump, resistant to norfloxacin; IS-58 strain carrying Tet(K), resistant to tetracyclines; RN4220 carrying MsrA, conferring resistance to erythromycin. For the EtBr fluorescence measurement test, K2068 carrying MepA was used. It was observed the individual sesquiterpenes exhibited better antibacterial activity as well as efflux pump inhibition. Farnesol showed the lowest MIC of 16.5 µg/mL against the S. aureus RN4220 strain. Isolated nerolidol stood out for reducing the MIC of EtBr to 5 µg/mL in the 1199B strain, yielding better results than the positive control CCCP, indicating strong evidence of NorA inhibition. The liposome formulations did not show promising results, except for liposome/farnesol, which reduced the MIC of EtBr against 1199B and RN4220. Further research is needed to evaluate the mechanisms of action involved in the inhibition of resistance mechanisms by the tested compounds.

Antibacterial Activity of the Essential Oil of Piper tuberculatum Jacq. Fruits against Multidrug-Resistant Strains: Inhibition of Efflux Pumps and ß-Lactamase.

Antimicrobial resistance has become a growing public health concern in recent decades, demanding a search for new effective treatments. Therefore, this study aimed to elucidate the phytochemical composition and evaluate the antibacterial activity of the essential oil obtained from the fruits of Piper tuberculatum Jacq. (EOPT) against strains carrying different mechanisms of antibiotic resistance. Phytochemical analysis was performed using gas chromatography-mass spectrometry (GC/MS). The antibacterial activity of EOPT and its ability to inhibit antibiotic resistance was evaluated through the broth microdilution method. The GC-MS analysis identified 99.59% of the constituents, with ß-pinene (31.51%), α-pinene (28.38%), and ß-cis-ocimene (20.22%) being identified as major constituents. The minimum inhibitory concentration (MIC) of EOPT was determined to assess its antibacterial activity against multidrug-resistant strains of Staphylococcus aureus (IS-58, 1199B, K2068, and K4100). The compound showed a MIC of ≥ 1024 µg/mL, suggesting a lack of intrinsic antibacterial activity. However, when the EOPT was associated with antibiotics and EtBr, a significant decrease in antibiotic resistance was observed, indicating the modulation of efflux pump activity. This evidence was corroborated with the observation of increased fluorescent light emission by the bacterial strains, indicating the involvement of the NorA and MepA efflux pumps. Additionally, the significant potentiation of ampicillin activity against the S. aureus strain K4414 suggests the ß-lactamase inhibitory activity of EOPT. These results suggest that the essential oil from P. tuberculatum fruits has antibiotic-enhancing properties, with a mechanism involving the inhibition of efflux pumps and ß-lactamase in MDR S. aureus strains. These findings provide new perspectives on the potential use of EOPT against antibiotic resistance and highlight the importance of Piper species as sources of bioactive compounds with promising therapeutic activities against MDR bacteria. Nevertheless, further preclinical (in vivo) studies remain necessary to confirm these in vitro-observed results.

Enhancement of the antibiotic activity mediated by the essential oil of Ocotea odorifera (VELL) ROWHER and safrole association.

In a recent study, our research group demonstrated that the essential oil of Ocotea odorifera (EOOO) and its major compound safrole potentiated the action fluoroquinolones, modulating bacterial resistance possibly due to direct inhibition of efflux pumps. Thus, in the present study, we investigated whether these treatments could enhance the activity of gentamicin and erythromycin against multidrug-resistant (MDR) bacteria. The EOOO was extracted by hydrodistillation, and the phytochemical analysis was performed by gas chromatography coupled to mass spectrometry (GC-MS). The antibiotic-enhancing effect of the EOOO and safrole against MDR strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa was analyzed by the broth microdilution method. The chemical analysis confirmed the presence of safrole as a major component among the 16 compounds identified in the EOOO. Both the essential oil and the isolated compound showed clinically relevant antibacterial activities against S. aureus. Regarding the modulation of antibiotic resistance, the EOOO was found to enhance the activity of erythromycin against the strains of P. aeruginosa and S. aureus, as well as improving the action of gentamicin against S. aureus. On the other hand, safrole potentiated the activity of gentamicin against the S. aureus strain alone. It is concluded, therefore, that the EOOO and safrole can enhance the activity of macrolides and aminoglycosides, and as such are useful in the development of therapeutic tools to combat bacterial resistance against these classes of antibiotics.