Infections caused by resistant strains of Acinetobacter baumannii are now a global problem that requires the immediate development of new antimicrobial drugs. Combination therapy is one of the strategies used to solve this problem. Based on this information, the purpose of this study was to determine whether quercetin (QUE), in combination with three antibiotics, is effective against colistin-resistant A. baumannii strains (ColR-Ab). The effects of the combination of QUE with colistin (COL), amikacin (AMK), and meropenem (MEM) were evaluated according to the checkerboard synergy test. The combinations of QUE + COL and QUE + AMK showed synergistic activity on ColR-Ab strains with FICI values in the range of 0.1875–0.5 and 0.1875–0.2825, respectively. A 4- to 16-fold decrease in COL MIC and a 16- to 64-fold decrease in AMK MIC values were detected. Synergistic activity was confirmed by the time-kill test, and these combinations were found to be bactericidal at the end of 24 h. According to spectrophotometric measurements, the combinations of QUE + COL and QUE + AMK induced membrane damage, leading to the leakage of nucleic acids. Cell lysis and cell death were confirmed with SEM observations. The detected synergy offers an opportunity for the future development of treatment strategies for potential infections caused by ColR-Ab strains.

Animal models designed to mimic certain features of Alzheimer's disease (AD) can help us to increase our understanding of the underlying mechanisms of disease. Previous studies have revealed that long-term D-galactose injection combined with ovariectomy results in pathophysiologic alterations associated with AD. Thus, the aim of the present study was to investigate the effects of rosmarinic acid (RA) administration on pathological changes associated with ovariectomy and D-galactose injection, which serve as a two-insult model for AD. One hundred female Wistar rats were divided into five equal groups: control (C), Sham (Sh), rosmarinic acid treated (R), ovariectomized rats treated with D-galactose (OD), ovariectomized rats treated with D-galactose and rosmarinic acid (ODR) groups. D-galactose (80 mg/kg/day) was administered by i.p. injection and RA (50 mg/kg/day) was given via gavage for 60 days. Open field and Y-maze tests were used to assess locomotor activity and short-term spatial memory, respectively. Biochemical and histopathological analyses of the brain tissue were performed. Open field testing showed that the locomotor activity and exploratory behavior of rats were prominently impaired in the OD group as compared to the other studied groups. Similarly, Y-maze test results revealed a decrease of short-term spatial memory in the OD rats. A concomitant treatment with RA significantly restored altered locomotor activity and cognitive functions in the ODR group. Lipid peroxidation levels, cyclooxygenase-2 expression and prostaglandin E2 levels in the brain tissue were higher in the OD group and RA treatment inhibited these changes. AD-like histopathological alterations and amyloid b peptide (Ab) depositions were observed in the OD group. Normal cell structure and lower Ab depositions were observed in the ODR group compared with the OD group. RA could have the potential to prevent some psychological and biochemical alterations of brain tissue found in a rat model of AD probably by attenuating lipid peroxidation and inflammatory response.

Colistin-resistant Acinetobacter baumannii (COLR-Ab) is an opportunistic pathogen commonly associated with nosocomial infections, and it is difficult to treat with current antibiotics. Therefore, new antimicrobial agents need to be developed for treatment. Based on this information, we investigated the antimicrobial, antibiofilm, and combination activities of p-coumaric acid (p-CA), ferulic acid (FA), and p-methoxycinnamic acid (p-MCA) against five COLR-Ab isolates. p-CA, FA, and p-MCA exhibited antimicrobial activity against COLR-Ab isolates, with minimum inhibitory concentration (MIC) values in the range of 256–128 µg/mL, 1024–512 µg/mL, and 512–128 µg/mL, respectively. The combination effects of the compounds with colistin (COL) were evaluated using a checkerboard synergy test. The combinations exhibited a synergistic effect and caused a 128- to 16-fold decrease in COL MIC values. In addition, the biofilm production capacities of the COLR-Ab isolates and the antibiofilm activities of the compounds were determined using the microtitre plate-based crystal violet (CV) technique. The compounds showed effective antibiofilm activity against strong and moderate biofilm-producing isolates, inhibiting biofilm formation by 77.5% and 19.7%. Spectrometric measurements were used to examine the effect of compounds on membrane permeability; 1.9-, 1.66-, and 1.34-fold increases in absorbance values were observed at MIC concentrations of p-CA, FA, and p-MCA, respectively. Furthermore, morphological changes caused by the compounds in the isolate were observed using scanning electron microscopy (SEM) micrographs. According to the WST assay, the compounds did not show any statistically significant cytotoxic effect on the cells (p > 0.05). These findings indicate that p-CA, FA, and p-MCA may be potential new alternative candidates against resistant A. baumannii.