The present study aimed to characterize the susceptibility profile of Pseudomonas aeruginosa and Acinetobacter spp. clinical isolates to polymyxin B in a public hospital in Recife‐PE, Brazil, between the years of 2018 and 2019, as well as to search for the presence of the mcr‐1 gene and evaluate the interaction between polymyxin B and usnic acid against these isolates. The strains were identified using the BD Phoenix™ automated system and the agar‐spot test was used to determine the susceptibility profile to polymyxin B. The minimum inhibitory concentrations (MICs) of usnic acid and polymyxin B were determined through the broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI). Subsequently, Polymerase Chain Reaction (PCR) was performed to detect the mcr‐1 gene in the isolates. The interaction between usnic acid and polymyxin B was evaluated by the Checkerboard assay. Among 34 isolates of P. aeruginosa, 26.5% (9/34) were positive for the polymyxin B agar‐spot test, and 11.8% (4/34) presented an intermediate susceptibility (MIC = 4 μg/mL), while 14.7% (5/34) presented antimicrobial resistance with MIC values ranging from 8 to 32 μg/mL. Among 38 isolates of Acinetobacter spp., 13.2% (5/38) were positive for the polymyxin B agar‐spot test and all of them were resistant to polymyxin B with a MIC value > 32 μg/mL. The mcr‐1 gene was not detected in the clinical isolates. Regarding usnic acid, it presented a moderate antibacterial activity against two P. aeruginosa isolates (MIC = 250 μg/mL) and no activity was detected against the others. A synergistic effect between usnic acid and polymyxin B was observed against three clinical isolates of P. aeruginosa which were resistant to polymyxin B (FICI ≤ 0.5). Therefore, it was possible to observe that usnic acid is a promising candidate to be used in combination with polymyxin B against infections caused by resistant P. aeruginosa.

Escherichia coli has been associated with the induction of colorectal cancer (CRC). Thus, combined therapy incorporating usnic acid (UA) and antibiotics such as ceftazidime (CAZ), co-encapsulated in liposomes, could be an alternative. Coating the liposomes with chitosan (Chi) could facilitate the oral administration of this nanocarrier. Liposomes were prepared using the lipid film hydration method, followed by sonication and chitosan coating via the drip technique. Characterization included particle size, polydispersity index, zeta potential, pH, encapsulation efficiency, and physicochemical analyses. The minimum inhibitory concentration and minimum bactericidal concentration were determined against E. coli ATCC 25922, NCTC 13846, and H10407 using the microdilution method. Antibiofilm assays were conducted using the crystal violet method. The liposomes exhibited sizes ranging from 116.5 ± 5.3 to 240.3 ± 3.5 nm and zeta potentials between +16.4 ± 0.6 and +28 ± 0.8 mV. The encapsulation efficiencies were 51.5 ± 0.2% for CAZ and 99.94 ± 0.1% for UA. Lipo-CAZ-Chi and Lipo-UA-Chi exhibited antibacterial activity, inhibited biofilm formation, and preformed biofilms of E. coli. The Lipo-CAZ-UA-Chi and Lipo-CAZ-Chi + Lipo-UA-Chi formulations showed enhanced activities, potentially due to co-encapsulation or combination effects. These findings suggest potential for in vivo oral administration in future antibacterial and antibiofilm therapies against CRC-inducing bacteria.

The aim of this study was to evaluate the phenotypic and molecular patterns of biofilm formation in infection and colonization isolates of Acinetobacter spp. from patients who were admitted in a public hospital of Recife-PE-Brazil in 2018-2019. For the biofilm phenotypic analysis, Acinetobacter spp. isolates were evaluated by the crystal violet staining method; the search of virulence genes (bap, ompA, epsA, csuE and bfmS) was performed by PCR; and the ERIC-PCR was performed for molecular typing. Amongst the 38 Acinetobacter spp. isolates, 20 were isolated from infections and 18 from colonization. The resistance profile pointed that 86.85% (33/38) of the isolates were multidrug-resistant, being three infection isolates, and two colonization isolates resistant to polymyxin B. All the isolates were able to produce biofilm and they had at least one of the investigated virulence genes on their molecular profile, but the bap gene was found in 100% of them. No clones were detected by ERIC-PCR. There was no correlation between biofilm formation and the resistance profile of the bacteria, neither to the molecular profile of the virulence genes. Thus, the ability of Acinetobacter spp. to form biofilm is probably related to the high frequency of virulence genes.

A utilização da biomassa para conversão em energia tem sido um tema muito abordado na atualidade, devido a importância da geração de energia limpa e renovável. Este estudo teve como objetivo analisar o potencial dendroenergético dos compartimentos da Acacia mearnsii De Wild. sob diferentes idades. Para isso, foi conduzido um estudo em dois povoamentos da espécie no estado do Rio Grande do Sul com idades de 1 a 7 anos. A biomassa foi mensurada por compartimento nas diferentes idades e, após esse processo, foi determinado o poder calorífico superior (PCS) das amostras. O cálculo da produtividade energética foi realizado pela multiplicação das variáveis biomassa e PCS. Mediante a análise de variância, evidenciou-se que existem diferenças significativas para o PCS dos compartimentos avaliados, tendo PCS médio para as folhas, a casca, os galhos vivos e a madeira, de 5.408, 4.787, 4.692 e 4.572 kcal kg-1, respectivamente. A produtividade energética da biomassa aumentou com o incremento da idade, com valores variando de 16,3 Gcal ha-1 para o plantio de um ano a 635 Gcal ha-1 para o povoamento de sete anos, sendo a madeira, o componente de maior contribuição para esses valores, exceto na primeira idade. Conclui-se que a espécie tem potencial para suprir futuras demandas energéticas e que a produtividade energética varia conforme a idade e o compartimento.