Antimicrobial Resistance and Biofilms Underlying Catheter-Related Bloodstream Coinfection by Enterobacter cloacae Complex and Candida parapsilosis.

Biofilm-associated infections are a public health concern especially in the context of healthcare-associated infections such as catheter-related bloodstream infections (CRBSIs). We evaluated the biofilm formation and antimicrobials resistance (AMR) of Enterobacter cloacae complex and Candida parapsilosis co-isolated from a CRBSI patient. Antimicrobial susceptibility of central venous catheters (CVCs) and hemoculture (HC) isolates was evaluated, including whole genome sequencing (WGS) resistome analysis and evaluation of gene expression to obtain insight into their AMR determinants. Crystal violet assay was used to assess dual biofilm biomass and microscopy was used to elucidate a microorganism's distribution within biofilms assembled on different materials. Bacteria were multidrug-resistant including resistance to colistin and beta-lactams, likely linked to the mcr-9-like phosphoethanolamine transferase and to an ACT family cephalosporin-hydrolyzing class C beta-lactamase, respectively. The R398I and Y132F mutations in the ERG11 gene and its differential expression might account for C. parapsilosis resistance to fluconazole. The phenotype of dual biofilms assembled on glass, polystyrene and polyurethane depends on the material and how biofilms were initiated by one or both pathogens. Biofilms assembled on polyurethane were denser and richer in the extracellular polymeric matrix, and microorganisms were differently distributed on the inner/outer surface of the CVC.

Wastewater-Aged Silver Nanoparticles in Single and Combined Exposures with Titanium Dioxide Affect the Early Development of the Marine Copepod Tisbe battagliai.

In this study, the effects of aged Ag and TiO2 nanoparticles (NPs), individually and as a mixture, in wastewater relative to their pristine counterparts on the development of the copepod nauplii (Tisbe battagliai) were investigated. NP behavior in synthetic wastewater and seawater was characterized during aging and exposure. A delayed development and subsequent mortality were observed after 6 days of exposure to aged Ag NPs, with a twofold decrease in EC50 (316 µg/L) compared to pristine NPs (EC50 640 µg/L) despite the similar dissolved Ag concentrations measured for aged and pristine Ag NPs (441 and 378 µg/L, respectively). In coexposures with TiO2 NPs, higher dissolved Ag levels were measured for aged NPs (238.3 µg/L) relative to pristine NPs (98.57 µg/L). Coexposure resulted in a slight decrease (15%) in the Ag NP EC50 (270 µg/L) with a 1.9-fold increase in the Ag NP retained within the organisms after depuration (2.82% retention) compared to Ag NP single exposures as measured with sp-ICP-MS, suggesting that the particles are still bioavailable despite the heteroaggregation observed between Ag, Ti NPs, and wastewater components. This study shows that the presence of TiO2 NPs can affect the stability and toxicity of Ag NPs in complex media that cannot be predicted solely based on ionic, total, or nanoparticulate concentrations, and the need for studying NP interactions in more complex matrices is highlighted.

Monitoring and modelling of influent patterns, phase distribution and removal of 20 elements in two primary wastewater treatment plants in Norway.

Many small- or medium-sized communities in Northern Europe employ only primary wastewater treatment plants (WWTPs) and effluent discharges can be a relevant source of pollution. The current study combines monitoring and modelling approaches to investigate concentrations, influent patterns, size distribution and removal of 20 elements for the two primary WWTPs (Ladehammeren, LARA; Høvringen, HØRA) serving Trondheim, the third largest city in Norway. Element concentrations were determined in raw influent wastewater, effluents and biosolids, and diurnal inflow patterns were assessed. The elemental distribution in particulate, colloidal and dissolved fractions of untreated wastewater was characterized using filtration separation and electron microscopy. An influent generator model and multivariate statistical analyses were used to determine release patterns and to predict the (co-)occurrence of selected elements. Raw influent wastewater concentrations for most elements were similar in the two WWTPs, with only Ca, Mn, Fe, Co and Ba being significantly higher (p < 0.05) in HØRA (which receives more household and hospital discharges). Removal efficiencies varied between elements, but in most cases reflected their association with particulates. Nanosized particles of several elements were detected, with Cu/Zn being most common. Measured concentrations of most elements followed typical diurnal wastewater discharge patterns and enrichment factors calculated for biosolids confirmed the importance of anthropogenic sources for P, Cu, Zn, Cd, As, Cr, Ni, Pb, V, Co and Fe. Elemental concentrations generally correlated well with total suspended solid (TSS) concentrations at HØRA, while this was less pronounced in LARA (possibly due to higher industrial contributions). In one of its first applications for WWTP influent pattern examination, principal component analysis was found to be instrumental for source identification of target elements, showing significant differences between LARA and HØRA influents. The combined experimental, statistical and modelling approaches used herein allowed for improved understanding of element sources, patterns of discharge and fate in primary WWTPs.

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS.

The ZnCr2O4/ZnO materials system has a wide range of potential applications, for example, as a photocatalytic material for waste-water treatment and gas sensing. In this study, probe-corrected high-resolution scanning transmission electron microscopy and geometric phase analysis were utilized to study the dislocation structure and strain distribution at the interface between zinc oxide (ZnO) and embedded zinc chromium oxide (ZnCr2O4) particles. Ball-milled and dry-pressed ZnO and chromium oxide (α-Cr2O3) powder formed ZnCr2O4 inclusions in ZnO with size ~400 nm, where the interface properties depended on the interface orientation. In particular, sharp interfaces were observed for ZnO [2113]/ZnCr2O4 [110] orientations, while ZnO [1210]/ZnCr2O4 [112] orientations revealed an interface over several atomic layers, with a high density of dislocations. Further, monochromated electron energy-loss spectroscopy was employed to map the optical band gap of ZnCr2O4 nanoparticles in the ZnO matrix and their interface, where the average band gap of ZnCr2O4 nanoparticles was measured to be 3.84 ± 0.03 eV, in contrast to 3.22 ± 0.01 eV for the ZnO matrix.

Nontuberculous mycobacteria pathogenesis and biofilm assembly.

Nontuberculous mycobacteria (NTM) are emergent pathogens whose importance in human health has been gaining relevance after being recognized as etiological agents of opportunist infections in HIV patients. Currently, NTM are recognized as etiological agents of several respiratory and extra-respiratory infections of immune-competent individuals. The environmental nature of NTM together with the ability to assemble biofilms on different surfaces plays a key role on their pathogenesis. In the present work the ability of three fast-growing NTM (Mycobacterium smegmatis, Mycobacterium fortuitum and Mycobacterium chelonae) to persist within a model of human alveolar macrophages was evaluated. Most often human infections with NTM occur by contact with the environment. Biofilms can work as environmental reservoirs. For this reason, it was decided to evaluate the ability of NTM to assemble biofilms on different surfaces. Scanning electron microscopy was used to elucidate the biofilm structure. The ability to assemble biofilms was connected with the ability to spread on solid media known as sliding. Biofilm assembly and intracellular persistence seems to be ruled by different mechanisms.

Exploring Dangerous Connections between Klebsiella pneumoniae Biofilms and Healthcare-Associated Infections.

Healthcare-associated infections (HAI) are a huge public health concern, particularly when the etiological agents are multidrug resistant. The ability of bacteria to develop biofilm is a helpful skill, both to persist within hospital units and to increase antibiotic resistance. Although the links between antibiotic resistance, biofilms assembly and HAI are consensual, little is known about biofilms. Here, electron microscopy was adopted as a tool to investigate biofilm structures associated with increased antibiotic resistance. The K. pneumoniae strains investigated are able to assemble biofilms, albeit with different kinetics. The biofilm structure and the relative area fractions of bacteria and extracellular matrix depend on the particular strain, as well as the minimal inhibitory concentration (MIC) for the antibiotics. Increased values were found for bacteria organized in biofilms when compared to the respective planktonic forms, except for isolates Kp45 and Kp2948, the MIC values for which remained unchanged for fosfomycin. Altogether, these results showed that the emergence of antimicrobial resistance among bacteria responsible for HAI is a multifactorial phenomenon dependent on antibiotics and on bacteria/biofilm features.

HOLZ rings in EBSD patterns of the UFeB4 compound: association with a random distribution of planar defects.

The UFeB4 phase present in different alloys of the B-Fe-U system was studied by powder X-ray diffraction (PXRD) and scanning electron microscopy complemented with energy-dispersive spectroscopy and electron backscattered diffraction (EBSD). The PXRD data showed that the ternary compound crystallized adopting essentially the YCrB4-type structure. However, microstructural observations revealed that under high undercooling conditions the UFeB4 phase exhibits a random distribution of defects parallel to, which are consistently associated with intense higher-order Laue zone rings in EBSD patterns. Indexation of the EBSD patterns showed that the defective structure is compatible with an intergrowth of YCrB4- and ThMoB4-type layers according to the (010)(YCrB4)//(110)(ThMoB4) and [001]YCrB4//[001](ThMoB4) orientation relation previously reported for an analogous compound. Magnetic studies indicated that the annealed UFeB4 compound has a paramagnetic behavior in the 2-300 K temperature range.