Gram‐negative bacteria produce outer membrane vesicles (OMVs) with 10 to 300 nm of diameter. The contribution of OMVs to bacterial pathogenesis is a topic of great interest, and their capacity to be combined with antigens impact in the future to the development of vaccines.

Atypical enteropathogenic Escherichia coli are capable to form biofilm on biotic and abiotic surfaces, regardless of the adherence pattern displayed. Several E. coli mechanisms are regulated by Quorum sensing (QS), including virulence factors and biofilm formation. Quorum sensing is a signaling system that confers bacteria with the ability to respond to chemical molecules known as autoinducers. Suppressor of division inhibitor (SdiA) is a QS receptor present in atypical enteropathogenic E. coli (aEPEC) that detects acyl homoserine lactone (AHL) type autoinducers. However, these bacteria do not encode an AHL synthase, but they are capable of sensing AHL molecules produced by other species, establishing an inter-species bacterial communication. In this study, we performed experiments to evaluate pellicle, ring-like structure and biofilm formation on wild type, sdiA mutants and complemented strains. We also evaluated the transcription of genes involved in different stages of biofilm formation, such as bcsA, csgA, csgD, fliC and fimA. The sdiA mutants were capable of forming thicker biofilm structures and showed increased motility when compared to wild type and complemented strains. Moreover, they also showed denser pellicles and ring-like structures. Quantitative real-time PCR (qRT-PCR) analysis demonstrated increased csgA, csgD and fliC transcription on mutant strains. Biofilm formation, as well as csgD, csgA and fimA transcription decreased on wild type strains by the addition of AHL. These results indicate that SdiA participates on the regulation of these phenotypes in aEPEC and that AHL addition enhances the repressor effect of this receptor on the transcription of biofilm and motility related genes.

Plastic biliary stents are a cost-effective treatment for biliary obstruction. Unfortunately, they have low patency, related to intraluminal biofilm formation. Silver nanoparticles (AgNPs) have been increasingly used in biomedicine because of its antibacterial properties. This study aimed to compare biofilm formation on stents with and without silver nanoparticle coatings when in contact with different bacterial culture medium. Different types of silver coatings were tested on plastic biliary stents. Two groups of stents were analyzed: one group with various types of silver nanoparticle coatings, and a negative control group with no coating. The stents were placed in different bacterial culture media and assessed for biofilm formation. Analysis was performed using confocal microscopy and direct colony-forming unit (CFU/cm²). Quantitative analysis showed promising results with C16 coating, as Escherichia coli ATCC and Pseudomonas aeruginosa ATCC exhibited reduced growth in the AgNP-coated group (p < 0.05). However, when mixed samples, including clinical strains and Staphylococcus aureus, were tested, the AgNP coating did not inhibit bacterial growth. AgNP-coated stents are effective against certain strains, such as E. coli ATCC and P. aeruginosa. Further research is needed to explore potential improvements in the coating mechanism.

Purpose: Plastic biliary stents are an effective treatment for biliary obstruction. Despite being resolutive and accessible, they are known to have a low patency rate, estimated at 3 to 6 months. This can be attributed to the formation of bacterial biofilm, which leads to the luminal obstruction of the stent. The aim of this study is to identify the bacterial composition of biofilms from obstructed plastic biliary stents removed through ERCP. Methods: Obstructed plastic biliary stents were retrieved from patients undergoing ERCP. The stents were fragmented into three segments of 2.0 cm each: proximal, medial, and distal. Gram staining was performed on each fragment, followed by assessment using optical microscopy. Subsequently, 4 μm cross-sections were made of each fragment, with subsequent analysis by confocal microscopy. The material from the inside of the stents was also placed in culture medium and colony-forming units were counted. Results: Optical microscopy and analysis by confocal microscopy showed a seemingly higher number of bacterial colonies in the distal portion of the stents compared to the proximal and medial regions. A greater presence of bacteria in the distal segments of the stents was confirmed, with growth reaching up to 10¹⁴, while growth in the proximal and medial segments was only observed up to 10⁹ and 10⁸, respectively. Biochemical identification using Gram staining identified both Gram-positive and Gram-negative species: Enterococcus faecium; Aeromonas hydrophila/caviae; Escherichia coli; Enterobacter cloacae; Citrobacter freundii; Klebsiella oxytoca; Proteus vulgaris; Proteus mirabilis; Pantoea sp; Morganella morganii. Conclusion: The composition of the biofilm in biliary stents confirmed to be polymicrobial. The distal portion of the stents is likely the most frequent site of obstruction. New strategies, such as the development and improvement of plastic stents, should be considered to slow this growth and enhance permeability.

Desenhamos e avaliamos primers para editar genomas de bactérias. Com o auxílio de ferramentas de bioinformática, planejamos primers capazes de remover o gene csgA de uma cepa de Escherichia coli e substituí-lo por um gene de resistência a antibiótico. Também verificamos se eram eficientes e específicos, garantindo que poderiam ser utilizados posteriormente em experimentos de edição genética e em estudos sobre o papel dessas bactérias na saúde humana.

A microbiota intestinal influencia funções digestivas, imunes e neurais por meio de moléculas microbianas. As fímbrias curli, formadas pela proteína curlina, estão associadas à neuroinflamação e à agregação de proteínas amiloides humanas. Contudo, os mecanismos moleculares que conectam curli e comunicação intestino-cérebro permanecem pouco esclarecidos. Assim, este estudo investigou possíveis interações entre curlina e proteínas hospedeiras humanas, fibronectina e integrina, por meio de análises de docking molecular e predição de cavidades.