Characterization and Evaluation of Layered Bi2WO6 Nanosheets as a New Antibacterial Agent

Background: Pathogenic microorganisms are causing increasing cases of mortality and morbidity, along with alarming rates of ineffectiveness as a result of acquired antimicrobial resistance. Bi2WO6 showed good potential to be used as an antibacterial substance when exposed to visible light. This study demonstrates for the first time the dimension-dependent antibacterial activity of layered Bi2WO6 nanosheets. Materials and methods: The synthesized layered Bi2WO6 nanosheets were prepared by the hydrothermal method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman and Fourier transform infrared spectroscopy (FTIR). Antibacterial and antibiotic-modulation activities were performed in triplicate by the microdilution method associated with visible light irradiation (LEDs). Results: Bi2WO6 nanosheets were effective against all types of bacteria tested, with MIC values of 256 µg/mL against Escherichia coli standard and resistant strains, and 256 µg/mL and 32 µg/mL against Staphylococcus aureus standard and resistant strains, respectively. Two-dimensional (2D) Bi2WO6 nanosheets showed antibacterial efficiency against both strains studied without the presence of light. Conclusions: Layered Bi2WO6 nanosheets revealed dimension-dependent antibacterial activity of the Bi2WO6 system.The authors thank Conselho Nacional de Desenvolvimento Científico e Tecnológico— CNPq, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES, and Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico—FUNCAP (Proc. BP4-00172-00232.01.00/20 and Proc. PR2-0101-00006.01.00/15) for the financial support. The authors would also like to thank the educational institutions UFCA, URCA, and UNILEÃO for their support during the experiments

Eco-epidemiological analysis of rickettsial seropositivity in rural areas of Colombia: A multilevel approach

ABSTARCT: Rickettsiosis is a re-emergent infectious disease without epidemiological surveillance in Colombia. This disease is generally undiagnosed and several deadly outbreaks have been reported in the country in the last decade. The aim of this study is to analyze the eco-epidemiological aspects of rickettsial seropositivity in rural areas of Colombia where outbreaks of the disease were previously reported. A cross-sectional study, which included 597 people living in 246 households from nine hamlets in two municipalities of Colombia, was conducted from November 2015 to January 2016. The survey was conducted to collect sociodemographic and household characteristics (exposure) data. Blood samples were collected to determine the rickettsial seropositivity in humans, horses and dogs (IFA, cut-off = 1/128). In addition, infections by rickettsiae were detected in ticks from humans and animals by real-time PCR targeting gltA and ompA genes. Data was analyzed by weighted multilevel clog-log regression model using three levels (person, household and hamlets) and rickettsial seropositivity in humans was the main outcome. Overall prevalence of rickettsial seropositivity in humans was 25.62% (95%CI 22.11-29.12). Age in years (PR = 1.01 95%CI 1.01-1.02) and male sex (PR = 1.65 95%CI 1.43-1.90) were risk markers for rickettsial seropositivity. Working outdoors (PR = 1.20 95%CI 1.02-1.41), deforestation and forest fragmentation for agriculture use (PR = 1.75 95%CI 1.51-2.02), opossum in peridomiciliary area (PR = 1.56 95%CI 1.37-1.79) and a high proportion of seropositive domestic animals in the home (PR20-40% vs 40% vs <20% = 3.14 95%CI 2.43-4.04) were associated with rickettsial seropositivity in humans. This study showed the presence of Rickettsia antibodies in human populations and domestic animals. In addition, different species of rickettsiae were detected in ticks collected from humans and animals. Our results highlighted the role of domestic animals as sentinels of rickettsial infection to identify areas at risk of transmission, and the importance of preventive measures aimed at curtailing deforestation and the fragmentation of forests as a way of reducing the risk of transmission of emergent and re-emergent pathogens