Typhoid fever imported from Mexico to Switzerland. Studies on R factor mediated chloramphenicol resistance

A case of typhoid fever caused by Salmonella typhi occurred in Geneva. The patient was probably infected in Mexico City. The strain isolated from this patient corresponds with the description of the Mexican S. typhi strain, since it is a degraded Vi-strain resistant to chloramphenicol, streptomycin, sulphonamides and tetracyclines. It carried an fi− transferable R factor with a CSSuT resistance pattern. It can be accepted that this case forms part of the Mexican outbreak of chloramphenicol-resistant typhoid fever which has already been observed in visitors to Mexico from England and the United State

Klebsiella pneumonia strains moderately resistant to ampicillin and carbenicillin: characterization of a new β-lactamase

Klebsiella pneumoniae strain 11-03, moderately resistant to ampicillin and carbenicillin, produces one constitutive β-lactamase with an isoelectric point of 7.10 and a molecular weight of 20,000±500. The enzymatic activity is directed primarily against the penicillins, ampicillin being the best substrate. Some cephalosporins are also hydrolyzed to some extent but the affinity of the enzyme for these antibiotics is low (high Km values). It has not been possible to determine whether the biogenesis of this β-lactamase is mediated by the bacterial chromosome or by a non-transferable plasmid. This β-lactamase appears to be different, on the basis of isoelectricfocusing, from an enzyme produced by the K pneumoniae strain GN422 (Sawal et al, 1973), but similar to the latter in several propertie

MosChito rafts as effective and eco-friendly tool for the delivery of a Bacillus thuringiensis-based insecticide to Aedes albopictus larvae

Adult mosquito females, through their bites, are responsible for the transmission of different zoonotic pathogens. Although adult control represents a pillar for the prevention of disease spread, larval control is also crucial. Herein we characterized the effectiveness of a suitable tool, named "MosChito raft", for the aquatic delivery of a Bacillus thuringiensis var. israelensis (Bti) formulate, a bioinsecticide active by ingestion against mosquito larvae. MosChito raft is a floating tool composed by chitosan cross-linked with genipin in which a Bti-based formulate and an attractant have been included. MosChito rafts (i) resulted attractive for the larvae of the Asian tiger mosquito Aedes albopictus, (ii) induced larval mortality within a few hours of exposure and, more importantly, (iii) protected the Bti-based formulate, whose insecticidal activity was maintained for more than one month in comparison to the few days residual activity of the commercial product. The delivery method was effective in both laboratory and semi-field conditions, demonstrating that MosChito rafts may represent an original, eco-based and user-friendly solution for larval control in domestic and peri-domestic aquatic habitats such as saucers and artificial containers in residential or urban environments

Parallel Evolution of Pseudomonas aeruginosa during a Prolonged ICU-Infection Outbreak.

Most knowledge about Pseudomonas aeruginosa pathoadaptation is derived from studies on airway colonization in cystic fibrosis; little is known about adaptation in acute settings. P. aeruginosa frequently affects burned patients and the burn wound niche has distinct properties that likely influence pathoadaptation. This study aimed to genetically and phenotypically characterize P. aeruginosa isolates collected during an outbreak of infection in a burn intensive care unit (ICU). Sequencing reads from 58 isolates of ST1076 P. aeruginosa taken from 23 patients were independently mapped to a complete reference genome for the lineage (H25338); genetic differences were identified and were used to define the population structure. Comparative genomic analysis at single-nucleotide resolution identified pathoadaptive genes that evolved multiple, independent mutations. Three key phenotypic assays (growth performance, motility, carbapenem resistance) were performed to complement the genetic analysis for 47 unique isolates. Population structure for the ST1076 lineage revealed 11 evolutionary sublineages. Fifteen pathoadaptive genes evolved mutations in at least two sublineages. The most prominent functional classes affected were transcription/two-component regulatory systems, and chemotaxis/motility and attachment. The most frequently mutated gene was oprD, which codes for outer membrane porin involved in uptake of carbapenems. Reduced growth performance and motility were found to be adaptive phenotypic traits, as was high level of carbapenem resistance, which correlated with higher carbapenem consumption during the outbreak. Multiple prominent linages evolved each of the three traits in parallel providing evidence that they afford a fitness advantage for P. aeruginosa in the context of human burn infection. IMPORTANCE Pseudomonas aeruginosa is a Gram-negative pathogen causing infections in acutely burned patients. The precise mechanisms required for the establishment of infection in the burn setting, and adaptive traits underpinning prolonged outbreaks are not known. We have assessed genotypic data from 58 independent P. aeruginosa isolates taken from a single lineage that was responsible for an outbreak of infection in a burn ICU that lasted for almost 2.5 years and affected 23 patients. We identified a core set of 15 genes that we predict to control pathoadaptive traits in the burn infection based on the frequency with which independent mutations evolved. We combined the genotypic data with phenotypic data (growth performance, motility, antibiotic resistance) and clinical data (antibiotic consumption) to identify adaptive phenotypes that emerged in parallel. High-level carbapenem resistance evolved rapidly, and frequently, in response to high clinical demand for this antibiotic class during the outbreak

Synthesis and characterisation of peroxypinic acids as proxies for highly oxygenated molecules (HOMs) in secondary organic aerosol

Peroxy acids were recently found to be involved in new particle formation in the atmosphere and could also substantially contribute towards particle toxicity. However, a lack of suitable analytical methods for the detection and characterisation of peroxy acids in the particle phase is currently hindering the quantitative investigation of their contribution to these important atmospheric processes. Further development of appropriate techniques and relevant standards is therefore urgently needed. In this study, we synthesised three peroxypinic acids, developed a liquid chromatography separation method and characterised them with tandem mass spectrometry. The observed fragmentation patterns clearly distinguish the different peroxypinic acids from both the acid and each other, showing several neutral losses previously already observed for other peroxy acids. Both monoperoxypinic acids were found to be present in secondary organic aerosol generated from ozonolysis of α-pinene in laboratory experiments. The yield of monoperoxypinic acid formation was not influenced by humidity. Monoperoxypinic acid quickly degrades on the filter, with about 60&thinsp;% lost within the first 5&thinsp;h. This fast degradation shows that time delays in traditional off-line analysis will likely lead to severe underestimates of peroxy compound concentrations in ambient particles.</p

3D Bioprinting of Pectin-Cellulose Nanofibers Multicomponent Bioinks

Pectin has found extensive interest in biomedical applications, including wound dressing, drug delivery, and cancer targeting. However, the low viscosity of pectin solutions hinders their applications in 3D bioprinting. Here, we developed multicomponent bioinks prepared by combining pectin with TEMPO-oxidized cellulose nanofibers (TOCNFs) to optimize the inks’ printability while ensuring stability of the printed hydrogels and simultaneously print viable cell-laden inks. First, we screened several combinations of pectin (1%, 1.5%, 2%, and 2.5% w/v) and TOCNFs (0%, 0.5%, 1%, and 1.5% w/v) by testing their rheological properties and printability. Addition of TOCNFs allowed increasing the inks’ viscosity while maintaining shear thinning rheological response, and it allowed us to identify the optimal pectin concentration (2.5% w/v). We then selected the optimal TOCNFs concentration (1% w/v) by evaluating the viability of cells embedded in the ink and eventually optimized the writing speed to be used to print accurate 3D grid structures. Bioinks were prepared by embedding L929 fibroblast cells in the ink printed by optimized printing parameters. The printed scaffolds were stable in a physiological-like environment and characterized by an elastic modulus of E = 1.8 ± 0.2&nbsp;kPa. Cells loaded in the ink and printed were viable (cell viability &gt;80%) and their metabolic activity increased in time during the in vitro culture, showing the potential use of the developed bioinks for biofabrication and tissue engineering applications

Embedded 3D printing for the development of perfusable in vitro 3D model of soft tissue

Hydrogels are widely investigated to develop 3D in vitro models for mimicking tissue microenvironment since their properties well match soft tissues ones. One concern is the lack of an adequate channel network, mimicking the tissue vascularization. Optimizing a vascularization strategy still remains challenging. We optimized and characterized a GelMA/Pluronic combination by using embedded 3D printing for the realization of a channel network in a GelMA scaffold