Evaluation of Gold Complexes to Address Bacterial Resistance, Quorum Sensing, Biofilm Formation, and Their Antiviral Properties against Bacteriophages.

The worldwide increase in antibiotic resistance poses a significant challenge, and researchers are diligently seeking new drugs to combat infections and prevent bacterial pathogens from developing resistance. Gold (I and III) complexes are suitable for this purpose. In this study, we tested four gold (I and III) complexes, (1) chlorotrimethylphosphine gold(I); (2) chlorotriphenylphosphine gold(I); (3) dichloro(2-pyridinecarboxylate) gold (III); and (4) 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene gold(I) chloride, for their antibacterial, antibiofilm, antiviral, and anti-quorum sensing activities. Results reveal that 1 significantly inhibits Escherichia coli DSM 1077 and Staphylococcus aureus ATCC 6538, while 2, 3, and 4 only inhibit S. aureus ATCC 6538. The minimum inhibitory concentration (MIC) of 1 for S. aureus ATCC 6538 is 0.59 µg/mL (1.91 µM), and for methicillin-resistant S. aureus strains MRSA 12 and MRSA 15, it is 1.16 µg/mL (3.75 µM). For E. coli DSM 1077 (Gram-negative), the MIC is 4.63 µg/mL (15 µM), and for multi-resistant E. coli I731940778-1, it is 9.25 µg/mL (30 µM). Complex 1 also disrupts biofilm formation in E. coli and S. aureus after 6 h or 24 h exposure. Moreover, 1 and 2 inhibit the replication of two enterobacteria phages. Anti-quorum sensing potential still requires further clarification. These findings highlight the potential of gold complexes as effective agents to combat bacterial and viral infections.

Ultrasound-Assisted Extraction of Polyphenols from Maritime Pine Residues with Deep Eutectic Solvents.

Deep eutectic solvents represent an important alternative in the field of green solvents due to their low volatility, non-toxicity, and low synthesis cost. In the present investigation, we propose the production of enriched polyphenolic extracts from maritime pine forest residues via an ultrasound-assisted approach. A Box-Behnken experimental design with a response surface methodology was used with six variables to be optimized: solid-to-solvent ratio, water percentage, temperature and time of extraction, amplitude, and catalyst concentration. The mixture of levulinic and formic acids achieved the highest extraction yield of polyphenols from pine needle and bark biomass. In addition, the solid-to-solvent ratio was found to be the only influential variable in the extraction (p-value: 0.0000). The optimal conditions were established as: 0.1 g of sample in 10 mL of LA:FA (70:30%, v/v) with 0% water and 0 M H2SO4 heated to 30 °C and extracted during 40 min with an ultrasound amplitude of 80% at 37 kHz. The bioactive properties of polyphenol-enriched extracts have been proven with significant antioxidant (45.90 ± 2.10 and 66.96 ± 2.75 mg Trolox equivalents/g dw) and antimicrobial activities. The possibility to recycle and reuse the solvent was also demonstrated; levulinic acid was successfully recovered from the extracts and reused in novel extractions on pine residues. This research shows an important alternative to obtaining polyphenol-enriched extracts from forest residues that are commonly discarded without any clear application, thus opening an important window toward the valorization of such residues.

The Preyssler-Type Polyoxotungstate Exhibits Anti-Quorum Sensing, Antibiofilm, and Antiviral Activities.

The increase in bacterial resistance to antibiotics has led researchers to find new compounds or find combinations between different compounds with potential antibacterial action and with the ability to prevent the development of antibiotic resistance. Polyoxotungstates (POTs) are inorganic clusters that may fulfill that need, either individually or in combination with antibiotics. Herein, we report the ability of the polyoxotungstates (POTs) with Wells-Dawson P2W18, P2W17, P2W15, and Preyssler P5W30 type structures to differently affect Gram-negative and Gram-positive microorganisms, either susceptible or resistant to antibiotics. The compound P5W30 showed the highest activity against the majority of the tested bacterial strains in comparison with the other tested POTs (P2W15, P2W17 and P2W18) that did not show inhibition zones for the Gram-negative bacteria, A. baumanii I73775, E. coli DSM 1077, E. coli I73194, K. pneumoniae I7092374, and P. aeruginosa C46281). Generally, the results evidenced that Gram-positive bacteria are more susceptible to the POTs tested. The compound P5W30 was the one most active against S. aureus ATCC 6538 and MRSA16, reaching <0.83 mg·mL−1 (100 µM) and 4.96 mg·mL−1 (600 µM), respectively. Moreover, it was verified by NMR spectroscopy that the most promising POT, P5W30, remains intact under all the experimental conditions, after 24 h at 37 °C. This prompted us to further evaluate the anti-quorum sensing activity of P5W30 using the biosensor Chromobacterium violaceum CV026, as well as its antibiofilm activity both individually and in combination with the antibiotic cefoxitin against the methicillin-resistant Staphylococcus aureus 16 (MRSA16). P5W30 showed a synergistic antibacterial effect with the antibiotic cefoxitin and chloramphenicol against MRSA16. Moreover, the antibiofilm activity of P5W30 was more pronounced when used individually, in comparison with the combination with the antibiotic cefoxitin. Finally, the antiviral activity of P5W30 was tested using the coliphage Qß, showing a dose-dependent response. The maximum inactivation was observed at 750 µM (6.23 mg·mL−1). In sum, P5W30 shows anti-quorum sensing and antibiofilm activities besides being a potent antibacterial agent against S. aureus and to exhibit antiviral activities against enteric viruses.

Inhalable chitosan microparticles for simultaneous delivery of isoniazid and rifabutin in lung tuberculosis treatment.

The direct delivery of antibiotics to the lung has been considered an effective approach to treat pulmonary tuberculosis, which represents approximately 80% of total cases. In this sense, this work aimed at producing inhalable chitosan microparticles simultaneously associating isoniazid and rifabutin, for an application in pulmonary tuberculosis therapy. Spray-dried chitosan microparticles were obtained with adequate flow properties for deep lung delivery (aerodynamic diameter of 4 µm) and high drug association efficiencies (93% for isoniazid and 99% for rifabutin). The highest concentration of microparticles that was tested (1 mg/mL) decreased the viability of macrophage-differentiated THP-1 cells to around 60% after 24 h exposure, although no deleterious effect was observed in human alveolar epithelial (A549) cells. The release of LDH was, however, increased in both cells. Chitosan microparticles further evidenced capacity to activate macrophage-like cells, inducing cytokine secretion well above basal levels. Moreover, the propensity of macrophages to internalize microparticles was demonstrated, with uptake levels over 90%. Chitosan microparticles also inhibited bacterial growth by 96%, demonstrating that the microencapsulation preserved drug antibacterial activity in vitro. Overall, the obtained data suggest the potential of chitosan microparticles for inhalable lung tuberculosis therapy.

Antimicrobial, antiviral and antioxidant activities of "água-mel" from Portugal.

"Água-mel" is a honey-based product produced in Portugal for ancient times. Several attributes have been reported to "água-mel" particularly in the alleviation of simple symptoms of upper respiratory tract. Samples of "água-mel" from diverse beekeepers from different regions of Portugal were studied in what concerns antimicrobial, antioxidant and antiviral properties. The amounts of phenol and brown pigment were also evaluated and correlated with the antioxidant activities. A great variability on the levels of these compounds was found among samples which were responsible for the variability detected also on the antioxidant activities, independent on the method used. Generally, antioxidant activity correlated better with brown pigments' amount than with phenols' content. The antimicrobial activity found for "água-mel" samples confirm the virtues reported by popular findings. In addition, this work also reveals the antiviral properties of "água-mel" evidenced by a decrease on the infectivity of the Qß bacteriophage.

Foeniculum vulgare essential oils: chemical composition, antioxidant and antimicrobial activities.

The essential oils from Foeniculum vulgare commercial aerial parts and fruits were isolated by hydrodistillation, with different distillation times (30 min, 1 h, 2 h and 3 h), and analyzed by GC and GC-MS. The antioxidant ability was estimated using four distinct methods. Antibacterial activity was determined by the agar diffusion method. Remarkable differences, and worrying from the quality and safety point of view, were detected in the essential oils. trans-Anethole (31-36%), alpha-pinene (14-20%) and limonene (11-13%) were the main components of the essentials oil isolated from F. vulgare dried aerial parts, whereas methyl chavicol (= estragole) (79-88%) was dominant in the fruit oils. With the DPPH method the plant oils showed better antioxidant activity than the fruits oils. With the TBARS method and at higher concentrations, fennel essential oils showed a pro-oxidant activity. None of the oils showed a hydroxyl radical scavenging capacity > 50%, but they showed an ability to inhibit 5-lipoxygenase. The essential oils showed a very low antimicrobial activity. In general, the essential oils isolated during 2 h were as effective, from the biological activity point of view, as those isolated during 3 h.

Susceptibility of Helicobacter pylori to essential oil of Dittrichia viscosa subsp. revoluta.

The essential oil of Dittrichia viscosa subsp. revoluta and its fractions were assessed for anti-Helicobacter activity. The essential oil was isolated by hydrodistillation, submitted to flash column chromatography and analysed by gas chromatography, gas-chromatography coupled to mass spectrometry and (13)C-nuclear magnetic resonance. The anti-Helicobacter activity was determined by incorporation of the crude essential oil and oxygenated fractions of the oil into the culture medium. At a concentration of 0.025 microL/mL no recovery was registered when one of the oxygenated fractions of the oil, mainly constituted by 3-methoxy cuminyl isobutyrate (about 40%), was used. This fraction revealed a higher activity against the six H. pylori strains tested when compared with the other oxygenated fractions. The crude essential oil at a concentration of 0.33 microL/mL reduced the initial population of H. pylori CCUG 15818 of 8.52 +/- 0.30 log(10) cfu/mL to 7.67 +/- 0.22 log(10) cfu/mL. The susceptibility of several Helicobacter pylori strains to the oxygenated fraction of Dittrichia viscosa subsp. revoluta essential oil suggests the possible use of these natural products in combating this widespread infection.

Occurrence and persistence of Listeria spp. in the environment of ewe and cow's milk cheese dairies in Portugal unveiled by an integrated analysis of identification, typing and spatial-temporal mapping along production cycle.

Eight dairies, located in two distant geographic regions of Portugal, were screened along the production cycle in order to evaluate the presence and distribution of Listeria spp. in their environment. Three dairies in each region were positive for the presence of listeriae and 213 isolates were obtained. Based on an integrated analysis of RAPD fingerprints with three primers, molecular identification and genomic typing of isolates was performed followed by spatial and temporal mapping on dairy plants. The occurrence of Listeria species by region was noticeable different. Listeria monocytogenes prevailed in South Portugal dairies and L. innocua presented the highest occurrence in Azores, whereas L. seeligeri and L. ivanovii were detected in distinct regions. Dairies were at risk of contamination, from more than one source, whatever the stage in the production cycle and the surface materials used. For the three prevalent species, most of the genomic types were dairy and sampling time specific. Nonetheless, more than one type could be found in each dairy at a particular site and, in a few cases, even for different species. Some dairies also shared types, mainly for L. innocua and usually at the same stage of the production cycle. For L. monocytogenes, PCR serotyping was applied and 52% of genomic types were serotype 4b. An equal frequency of genomic types (24%) was found for serotypes 1/2b or 3b and 1/2a or 3a. The global pattern of types within a dairy is not constant, suggesting cycles of elimination and recontamination along the production cycle.

Antibacterial and antioxidant activities of essential oils isolated from Thymbra capitata L. (Cav.) andOriganum vulgare L.

Antilisterial activities of Thymbra capitata and Origanum vulgare essential oils were tested against 41 strains of Listeria monocytogenes. The oil of T. capitata was mainly constituted by one component, carvacrol (79%), whereas for O. vulgare three components constituted 70% of the oil, namely, thymol (33%), gamma-terpinene (26%), and p-cymene (11%). T. capitata essential oil had a significantly higher antilisterial activity in comparison to O. vulgare oil and chloramphenicol. No significant differences in L. monocytogenes susceptibilities to the essential oils tested were registered. The minimum inhibitory concentration values of T. capitata essential oil and of carvacrol were quite similar, ranging between 0.05 and 0.2 microL/mL. Antioxidant activity was also tested, the essential oil of T. capitata showing significantly higher antioxidant activity than that of O. vulgare. Use of T. capitata and O. vulgare essential oils can constitute a powerful tool in the control of L. monocytogenes in food and other industries.