Nanoscale Phenotypic Textures of Yersinia pestis Across Environmentally-Relevant Matrices.

The persistence of bacterial pathogens within environmental matrices plays an important role in the epidemiology of diseases, as well as impacts biosurveillance strategies. However, the adaptation potentials, mechanisms for survival, and ecological interactions of pathogenic bacteria such as Yersinia pestis are largely uncharacterized owing to the difficulty of profiling their phenotypic signatures. In this report, we describe studies on Y. pestis organisms cultured within soil matrices, which are among the most important reservoirs for their propagation. Morphological (nanoscale) and phenotypic analysis are presented at the single cell level conducted using Atomic Force Microscopy (AFM), coupled with biochemical profiles of bulk populations using Fatty Acid Methyl Ester Profiling (FAME). These studies are facilitated by a novel, customizable, 3D printed diffusion chamber that allows for control of the external environment and easy harvesting of cells. The results show that incubation within soil matrices lead to reduction of cell size and an increase in surface hydrophobicity. FAME profiles indicate shifts in unsaturated fatty acid compositions, while other fatty acid components of the phospholipid membrane or surface lipids remained consistent across culturing conditions, suggesting that phenotypic shifts may be driven by non-lipid components of Y. pestis.

Synthesis and sensitive detection of doxycycline with sodium bis 2-ethylhexylsulfosuccinate based silver nanoparticle.

The monitoring of residual antibiotics in the environment has gained a significant importance for the effective control, because of the high risk to human health. A simple strategy was designed for the green synthesis and detection of doxycycline (Dox) by using anionic surfactant sodium bis 2-ethylhexylsulfosuccinate based silver nanoparticles (AOT-AgNPs). The chemical reduction and capping of Ag+1 ions was achieved by sulfonyl and carbonyl functional groups of AOT molecule. The AOT-AgNPs were found to have excellent stability at variable environmental parameters (i.e. temperature, storage period, salt concentration and pH) possibly due to the strong emulsifying nature of the surfactant. Mechanism of interaction between the AOT-AgNPs and Dox was established with UV/visible, Fourier transform infrared (FTIR) spectroscopy, Atomic force microscopy (AFM) and Dynamic light scattering (DLS) techniques, which suggests the interaction via aggregates formation. The synthesize probe could detect the Dox within 15 min over a wide range of concentrations from 0.1 to 140µM with limit of detection (LOD) of 0.2 µM. As proof of strategy, we have illustrated that the AOT-AgNPs also detect Dox in biological and environmental samples with negligible interference and very significant recovery rates. Moreover, non-toxic nature against various tested cell lines (i.e. normal mouse fibroblast (NIH-3 T3) and cancerous non-small lung carcinoma (NCI-H460)) and significant antimicrobial, antibiofilm and biofilm eradicating potential of AOT-AgNPs were provide ideal nanomaterial for further applications.

Customizable 3D printed diffusion chambers for studies of bacterial pathogen phenotypes in complex environments.

Gaps in our understanding of the natural ecology and survival mechanisms of pathogenic bacteria in complex microenvironments such as soil typically occur due to the difficulty in characterizing biochemical profiles and morphological characteristics as they exist in environmental samples. Conversely, accurate simulation of the abiotic and biotic chemistries of soil habitats within the laboratory is often a significant challenge. Herein, we present the fabrication of customizable and precisely engineered 3D printed diffusion chambers that can be used to incubate bacterial cultures directly in soil matrices within a controlled laboratory experiment, and study the dynamics between bacterial cells and soil components. As part of the design process, different types of 3D printing materials were evaluated for ease of sterilization, structural integrity throughout the experiment, as well as cost/ease of production. To demonstrate potential applications for environmental studies, the diffusion chamber was used to incubate cultures of Bacillus cereus T-strain and Escherichia coli strain O157 directly in soil matrices. We show that the chamber facilitates diffusion of abiotic/biotic components of the soil with target cells without contamination from in situ microbial communities, while allowing for single cell and ensemble level phenotypic analyses of bacteria cultured with and without soil matrices.

Staphylococcus aureus Bacteremia in Children of Rural Areas of The Gambia, 2008-2015.

Staphylococcus aureus bacteremia is a substantial cause of childhood disease and death, but few studies have described its epidemiology in developing countries. Using a population-based surveillance system for pneumonia, sepsis, and meningitis, we estimated S. aureus bacteremia incidence and the case-fatality ratio in children <5 years of age in 2 regions in the eastern part of The Gambia during 2008-2015. Among 33,060 children with suspected pneumonia, sepsis, or meningitis, we performed blood culture for 27,851; of 1,130 patients with bacteremia, 198 (17.5%) were positive for S. aureus. S. aureus bacteremia incidence was 78 (95% CI 67-91) cases/100,000 person-years in children <5 years of age and 2,080 (95% CI 1,621-2,627) cases/100,000 person-years in neonates. Incidence did not change after introduction of the pneumococcal conjugate vaccine. The case-fatality ratio was 14.1% (95% CI 9.6%-19.8%). Interventions are needed to reduce the S. aureus bacteremia burden in The Gambia, particularly among neonates.

Lack of equivalence between central and mixed venous oxygen saturation.

STUDY OBJECTIVE: We compared paired samples of central venous O(2) saturation (Scvo(2)) and mixed venous O(2) saturation (Svo(2)) to test the hypothesis that Scvo(2) is equivalent to Svo(2). We also compared O(2) consumption (Vo(2)) computed with Scvo(2) (Vo(2)cv) to that computed with Svo(2) (Vo(2)v). DESIGN: Prospective, sequential, observational study. SETTING: Combined medical-surgical ICU. PATIENTS: Fifty-three individuals > 18 years of age of either sex who required a pulmonary artery catheter (PAC) to guide fluid therapy. Subjects were identified as postsurgical (32 patients) or medical (21 patients) according to their ICU admission diagnosis. INTERVENTIONS: A PAC was inserted through the internal jugular or subclavian veins. Care was taken to place the PAC proximal port approximately 3 cm above the tricuspid valve. Blood samples were drawn from the proximal and distal ports in random order. An arterial blood sample also was drawn. MEASUREMENTS: Cardiac output in triplicate, systemic pressure, and central pressure. We analyzed blood samples for hemoglobin concentration and O(2) saturation (So(2)). Data were compared by correlation analysis and by the method of Bland and Altman. RESULTS: Svo(2) was consistently lower than Scvo(2) (p < 0.0001), with a mean (+/-SD) bias of -5.2 +/- 5.1%. Similar differences in Scvo(2) and Svo(2) were present within each subgroup (p < 0.001). A lower Svo(2) resulted in Vo(2)v values that were higher than the Vo(2)cv values for all patients in the study (mean Vo(2)v, 236.7 +/- 103.4 mL/min; mean Vo(2)cv, 191.1 +/- 84.0 mL/min; p < 0.001) as well as for patients within each subgroup (p < 0.001). CONCLUSIONS: Measurements of Scvo(2) and Svo(2) were not equivalent in this sample of critically ill patients. Moreover, substituting Scvo(2) for Svo(2) in the calculation of Vo(2) produced unacceptably large errors. The decrease in So(2) between Scvo(2) to Svo(2) may result from the mixing of atrial and coronary sinus blood. As such, this difference may be a marker of myocardial O(2) consumption.