A worrisome fact is the increase in microbial resistance, which has as its main cause the indiscriminate use of antibiotics. Scientific studies have investigated bioactive compounds such as steroidal sapogenins, in the perspective of new beneficial alternatives for the control of bacterial resistance. Therefore, the objective of this work was to verify the antibacterial activity as well as the modifying action of antibiotics associated with solasodine and its ability to inhibit the efflux pump mechanism in strains of Staphylococcus aureus. Tests were performed to verify the minimum inhibitory concentration (MIC). In addition, the action-modifying potential of antibiotics and the inhibitory capacity of the efflux pump NorA and MepA through synergistic effects on the antibiotic and ethidium bromide were evaluated. Solasodine showed significant results for the standard bacteria with an MIC of 512 μg/mL, and when associated with the antibiotics gentamicin and nofloxacin for the multidrug-resistant bacteria S. aureus 10, Escherichia coli 06, and Pseudomonas aeruginosa 24, it showed a 50% reduction in MIC. The association of solasodine with the antibiotic ciprofloxacin against S. aureus K2068 (MepA) showed synergism, with a reduction in the MIC of the antibiotic from 64 μg/mL to 40 μg/mL, and also a reduction in the MIC when the antibiotic was used in conjunction with the efflux pump inhibitors. Solasodine may be acting on the mechanism of action of the antibiotic, as it has shown a potentiating effect when associated with antibiotics, inducing a reduction in the MIC against Gram-positive and Gram-negative bacteria. Therefore, this study demonstrated significant results for the potentiating action of solasodine when associated with antibiotics of clinical importance.

Titanium nanotubes have attractive morphological and physicochemical properties for several applications, such as high surface area, mesoporous structure, good stability, ion exchange capacity, and antibacterial property. Therefore, the field of nanotube applications is increasingly expanding, such as in solar cells sensitized by dye, photocatalysis, and antibacterial activity, among others. Therefore, a study of the antibacterial properties of sodium titanate nanotubes (Na‐TiNTs) was carried out together with physicochemical characterizations, such as Raman spectroscopy which shows a peak characteristic of Na‐O‐Ti from nanotube‐agglomerated regions. The XRD diffractogram confirmed the Raman spectra and evidenced the crystalline structure associated to Na‐TiNT, which showed the characteristic peaks of the sodium trititanate crystal. SEM and TEM images showed the morphology of hollow nanotubes and forming semispherical particles. EDS shows the percentage values of each of the compounds in the Na‐TiNT. The bacterial activity of the Na‐TiNT was analyzed in Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Na‐TiNT modified the activity of the gentamicin and norfloxacin antibiotics against multiresistant strains. Synergistic effects against Gram‐positive S. aureus 10 and Gram‐negative P. aeruginosa 15 bacteria were observed when the Na‐TiNT was associated with gentamicin, reducing the concentration of this antibiotic that is required to inhibit bacterial growth. Another synergic effect was observed for S. aureus 10 with norfloxacin.

As the spread of bacterial resistance to clinically available antibiotics has become a global public health problem, the scientific community has intensified its studies in the search for natural compounds and their derivatives to combat bacterial resistance. In this work, a circadian study of the essential oil extracted from the leaves of Croton piauhiensis (EOCP) was carried out. We also sought to evaluate its antibacterial activity, modulatory potential and if it acts as a possible inhibitor of the efflux pump by determining the minimum inhibitory concentration (MIC) and the association of the oil in subinhibitory concentrations with the antibiotic ciprofloxacin and with ethidium bromide (EtBr) against the strain of Staphylococcus aureus K2068 strain. The assays used to obtain the MIC of the EOCP were performed by broth microdilution, while the efflux pump inhibitory test was performed by the MIC modification method. According to the results, the circadian study showed differences in the chemical composition and percentage of oils collected at different times of the day, which can be attributed to environmental conditions. The main components of the EOCP were β-caryophyllene (6 h—21.23%; 12 h—22.86% and 18 h—16.95%), followed by D-Limonene (6 h—13.27% and 18 h—15.95%) and γ-Elemene (12 h)—12.61%). The EOCP collected at 12 h had a better profile in reducing MIC, presenting antibacterial activity for Staphylococcus aureus and Escherichia coli. In the efflux pump test, it was observed that the oil was able to potentiate the action of ethidium bromide against the S. aureus K2068 strain, which can contribute to the prevention or treatment of infectious diseases caused by multidrug-resistant (MDR) strains.

Bacterial biofilms have been the subject of studies, mainly because they are responsible for a significant fraction of persistent infections that are resistant to both the action of antimicrobials and the action of the host’s immune system. Staphylococcus aureus is a pathogen with remarkable virulence, present in a significant portion of infectious diseases that affect humans, and its ability to form biofilms contributes to the risks associated with outbreaks involving this agent. This chapter aims to highlight and understand the molecular components involved in the formation and maturation of S. aureus biofilms, as well as the host’s immune responses. These factors are crucial for developing effective strategies to overcome the resistance barrier imposed by biofilms, with the goal of implementing more effective treatments and improving patients’ quality of life. Additionally, the chapter will address the current therapies available for treating infections caused by S. aureus biofilms.