Investigation of factors related to biofilm formation in Providencia stuartii.

Providencia stuartii is one of the Enterobacteriaceae species of medical importance commonly associated with urinary infections, which can also cause other ones, including uncommon ones, such as liver abscess and septic vasculitis. This bacterium stands out in the expression of intrinsic and acquired resistance to antimicrobials. Besides, it uses mechanisms such as biofilm for its persistence in biotic and abiotic environments. This study investigated the cellular hydrophobicity profile of clinical isolates of P. stuartii. It also analyzed genes related to the fimbrial adhesin in this species comparing with other reports described for other bacteria from Enterobacteriaceae family. The investigated isolates to form biofilm and had a practically hydrophilic cell surface profile. However, fimH and mrkD genes were not found in P. stuartii, unlike observed in other species of Enterobacteriaceae. These results show that P. stuartii has specificities regarding its potential for biofilm formation, which makes it difficult to destabilize the infectious process and increases the permanence of this pathogen in hospital units.

Identification of a critical binding site for local anaesthetics in the side pockets of Kv 1 channels.

BACKGROUND AND PURPOSE: Local anaesthetics block sodium and a variety of potassium channels. Although previous studies identified a residue in the pore signature sequence together with three residues in the S6 segment as a putative binding site, the precise molecular basis of inhibition of Kv channels by local anaesthetics remained unknown. Crystal structures of Kv channels predict that some of these residues point away from the central cavity and face into a drug binding site called side pockets. Thus, the question arises whether the binding site of local anaesthetics is exclusively located in the central cavity or also involves the side pockets. EXPERIMENTAL APPROACH: A systematic functional alanine mutagenesis approach, scanning 58 mutants, together with in silico docking experiments and molecular dynamics simulations was utilized to elucidate the binding site of bupivacaine and ropivacaine. KEY RESULTS: Inhibition of Kv 1.5 channels by local anaesthetics requires binding to the central cavity and the side pockets, and the latter requires interactions with residues of the S5 and the back of the S6 segments. Mutations in the side pockets remove stereoselectivity of inhibition of Kv 1.5 channels by bupivacaine. Although binding to the side pockets is conserved for different local anaesthetics, the binding mode in the central cavity and the side pockets shows considerable variations. CONCLUSION AND IMPLICATIONS: Local anaesthetics bind to the central cavity and the side pockets, which provide a crucial key to the molecular understanding of their Kv channel affinity and stereoselectivity, as well as their spectrum of side effects.

Saline extract from Malpighia emarginata DC leaves showed higher polyphenol presence, antioxidant and antifungal activity and promoted cell proliferation in mice splenocytes.

Currently, the research of new natural compounds with biological potential demonstrates great ethnopharmacological importance. In this study, we evaluated the biological properties promoted by saline extract from Malpighia emarginata DC leaves, whose objective is to evaluate the antioxidant, antimicrobial and cytotoxicity potential. Phytochemical characterization was performed by UPLC-MS chromatography to identify the chemical compounds. For the antioxidant potential, DPPH, ATT and FRAP methods were used. The antibacterial and antifungal tests were performed evaluating the MIC50, MIC90, CMB and CMF parameters. Moreover, antibiofilm action was evaluated. Cytotoxicity and proliferation were performed using splenocytes from Balb/c mice and were evaluated by cytometry. We found a list of phenolic compounds among other bioactive compounds in the M. emarginata saline extract. In addition, higher antioxidant profile and antifungal activity against different strains of Candida spp. was promoted by the saline extract. Splenocytes showed greater cell viability (more than 90%) and showed higher proliferate index in 24 and 48 hours of incubation with the extract. Saline extract from Malpighia emarginata DC has potential action like antioxidant and antifungal agent without promote animal cell damage.