Cell envelope growth of Gram-negative bacteria proceeds independently of cell wall synthesis

All bacterial cells must expand their envelopes during growth. The main load-bearing and shape-determining component of the bacterial envelope is the peptidoglycan cell wall. Bacterial envelope growth and shape changes are often thought to be controlled through enzymatic cell wall insertion. We investigated the role of cell wall insertion for cell shape changes during cell elongation in Gram-negative bacteria. We found that both global and local rates of envelope growth of Escherichia coli remain nearly unperturbed upon arrest of cell wall insertion-up to the point of sudden cell lysis. Specifically, cells continue to expand their surface areas in proportion to biomass growth rate, even if the rate of mass growth changes. Other Gram-negative bacteria behave similarly. Furthermore, cells plastically change cell shape in response to differential mechanical forces. Overall, we conclude that cell wall-cleaving enzymes can control envelope growth independently of synthesis. Accordingly, the strong overexpression of an endopeptidase leads to transiently accelerated bacterial cell elongation. Our study demonstrates that biomass growth and envelope forces can guide cell envelope expansion through mechanisms that are independent of cell wall insertion.

Synthesis of tetrahydrocarbazoles through a radical cation [4+2] cycloaddition reaction of 2-vinylindoles

A redox umpolung strategy for the synthesis of complex tetrahydrocarbazoles is reported. The reaction involves a visible light promoted radical cation [4+2] cycloaddition between 2-vinylindoles and conjugated alkenes that proceeds with good yields and diastereoselectivity.

Poloxamer-Based Hydrogel as Drug Delivery System: How Polymeric Excipients Influence the Chemical-Physical Properties

Thermogelling amphiphilic block copolymers have been widely investigated in the development of pharmaceutical drug carriers. In particular, thermosensitive gels based on poloxamer 407 (P407) have great potential for periodontal disease treatment, thanks to their ability to be liquid at room temperature and become viscous gels at body temperature. However, some problems, related to short in situ residence time, reduce their feasible clinical use. Thus, in order to improve the effective applicability of these materials, we studied how P407 thermogels are affected by the pH and by the inclusion of different hydrophilic polymers, used as excipients for increasing the gel stiffness. For this scope, a complete chemical-physical characterization of the synthesized gels is provided, in terms of determination of sol-gel transition temperature, viscosity and erosion degree. The data are correlated according to a statistical multivariate approach based on Principal Component Analysis and their mucoadhesion properties are also tested by Tapping mode-Atomic Force Microscopy (TM-AFM) imaging. Finally, we studied how the different P407 formulations are able to influence the release pathway of two antibacterial drugs (i.e., chlorhexidine digluconate and doxycycline hyclate) largely used in oral diseases.

Biodegradable floating hydrogel baits as larvicide delivery systems against mosquitoes

Biological methods for mosquito larvae control are completely biodegradable and have null or limited effects on nontarget organisms. However, commercially available products have a low residual activity, with the consequent need for multiple applications that inevitably increase costs and the risk of resistance phenomena insurgence. Smart delivery systems made of hydrogels proved their efficacy in increasing the action duration of biolarvicides up to several months, but the lack of an efficient baiting mechanism to strongly attract the target pest remains a problem in practical applications. In this work, we investigated two novel hydrogel-based formulations of completely natural composition for baiting and killing larvae of Aedes albopictus mosquitos. The proposed materials consist of charged crosslinked polysaccharides (chitosan and cellulose) and are specifically manufactured to float in water, simulating organic matter usually present at breeding sites. Within the hydrogels' matrix, yeast colonies of Saccharomyces cerevisiae were embedded as phagostimulants alongside a biolarvicide (Bacillus thuringiensis var. israelensis (Bti)). Despite the similar chemical nature and structure, chitosan-based hydrogels exhibited a markedly superior baiting potential compared to those made of cellulose and also succeeded in efficiently killing mosquito larvae just after a few hours from administration. We are confident that the proposed smart delivery hydrogel made of chitosan can be an enabling tool to attract mosquito larvae towards biopesticides of different nature without delocalizing active ingredients away from the breeding site and to simultaneously increase their residual activity, thus holding the potential of minimizing environmental pollution related to pest control and vector-borne disease prevention.

Microbial contamination of resin composites inside their dispensers: An increased risk of cross-infection?

OBJECTIVES

To evaluate the effects of microorganisms' contamination inside the dispensing syringes of different types of resin-based composites (RBCs).

METHODS

This study encompassed two sections. First, an anonymous electronic survey was submitted via Google forms to Italian dentists to acquire information about composite handling during clinical procedures. Then, a bench test was performed on nanohybrid RBCs differing in matrix chemistry and fillers [FiltekTM Supreme XTE (3MTM); Venus Pearl (Kulzer GmbH); Admira Fusion x-tra (Voco)] to evaluate the microbial viability on their surfaces with/out photocuring. Uncured RBCs were exposed to standardized inocula of Streptococcus Mutans, Candida Albicans, Lactobacillus Rhamnosus, or mixt plaque in an in vitro model reproducing clinical restorative procedures. Half of the RBC specimens were cured after exposure. Microbial viability was assessed using an MTT-based test. Statistical analysis included three-way ANOVA and Tukey's tests (p<0.05).

RESULTS

Among 300 dentists completing the survey, the majority declared to use the spatula to carry the RBCs from the syringe to the dental cavity (50% same spatula; 35% two spatulas). However, 80% of respondents had personal feelings that using one spatula could be a source of cross-contamination. In vitro results using one spatula showed microbial contamination of all RBCs after one hour of storage. The contamination levels depended on the used strain and RBC type (p<0.0001), but photocuring did not reduce contamination (p = 0.2992).

CONCLUSIONS

Microbial species' viability on uncured RBCs and after photocuring shows the existence of a considerable risk of cross-infection. Clinical procedures in Restorative Dentistry need to acknowledge and to reduce such risk during RBCs handling.

CLINICAL SIGNIFICANCE

Dentists must be aware of the possibility of cross-infection during restorative procedures, especially when the same spatula is repeatedly used for placing RBC in the cavity.

Synthesis and photophysical evaluation of polarity sensitive push-pull isoquinolines and their alkynyl precursors

Two sets of unprecedented push-pull isoquinolines, characterized by an opposite "dipolar moment" with respect to the longitudinal axis of the molecule, have been prepared. The key step of the approach is the microwave-promoted domino imination/cycloisomerization of 2-alkynyl benzaldehydes in the presence of methanolic ammonia. Absorption spectra and emission spectra of the D-π-A isoquinolines and their alkynyl precursors in nine different solvents have been recorded. The absolute QYs of all compounds have been recorded in three solvents with different polarities, i.e. toluene, DMSO and ethanol. Among the D-π-A isoquinolines prepared - nicknamed QuinaChroms - two compounds characterized by opposite dipolar moments, i.e. 3-(4-methoxyphenyl)-7-nitroisoquinoline 1a and N,N-diethyl-3-(4-(methylsulfonyl)phenyl)isoquinolin-7-amine 2b displayed more interesting photophysical profiles, whereas 5-(diethylamino)-2-(A)arylethynylbenzaldehydes precursors 8a-c - having a free aldehyde group that is suitable for possible conjugation - exhibited strong fluorescence and wide Stokes shifts. These products are interesting for potential use as polarity-sensitive fluorescent probes or advanced functional materials.

Can Pseudomonas aeruginosa growth be modulated by natural compounds?

Pseudomonas aeruginosa is an opportunistic human pathogen that frequently induces antibiotic resistance, as it mainly tends to form biofilms. Iron chelation may be an intriguing strategy to contrast bacterial growth. Lactoferrin is a natural compound able to chelate iron. A new multi-component medical device also contains lactoferrin. This study analyzed this compound investigating the in vitro capacity to inhibit Pseudomonas aeruginosa growth. In conclusion, this study demonstrated that a multicomponent medical device (Saflovir), also containing lactoferrin, could inhibit the in vitro growth of P. aeruginosa. This activity could be positively used in the prevention of respiratory nasal infections.

Stereoselective synthesis of 2-spirocyclopropyl-indolin-3-ones through cyclopropanation of aza-aurones with tosylhydrazones

A simple and efficient approach for the synthesis of 2-spirocyclopropyl-indolin-3-ones is herein described. The method involves a diasteroselective cyclopropanation of aza-aurones with tosylhydrazones, selected as versatile carbene sources, and represents a remarkable synthetic alternative to get access to this class of C2-spiropseudoindoxyl scaffolds. The reactions proceed in the presence of a base and catalytic amounts of benzyl triethylammonium chloride and well-tolerate a broad range of substituents on both aza-aurones and tosylhydrazones to afford a series of C2-spirocyclopropanated derivatives in high yields. In addition, selected functional group transformations of the final products were explored demonstrating the synthetic potential of these indole-based derivatives.

A new urinary catheter design reduces in-vitro biofilm formation by influencing hydrodynamics

AIM

To evaluate the performance of a new catheter design based on different hydrodynamics aiming to reduce the development of biofilm, and compare it with a conventional Foley catheter (FC).

METHODS

The new proposed design (NPD) catheter is a modification of the FC, based on asymmetric positioning of the balloon and additional drainage holes allowing continuous urine drainage and complete voiding of the bladder. A first experiment was undertaken to assess drainage capability, and a second experiment was performed using a bioreactor with a set-up simulating the bladder and using the test catheter as a flow-through system. The biofilm formation of five bacterial species associated with catheter-associated urinary tract infection (CAUTI) was determined after 24 h of incubation using an MTT assay. Morphological evaluation was performed using scanning electron microscopy. In-vitro determination of residual fluid, and quantitative and morphological data on biofilm formation on the intravesical and intraluminal parts of the tested catheters were assessed.

RESULTS

Residual fluid was significantly higher in the FC (5.60 ± 0.43 mL) compared with the NPD catheter (0.2 ± 0.03 mL). The NPD catheter showed significantly less biofilm formation (P<0.0001) than the FC. Catheter design had a variable effect on biofilm formation depending on the bacterial strain tested. There was significantly less intraluminal biomass compared with intravesical biomass in both catheters (P<0.0001). Multi-layered biofilms that covered the FC surfaces completely were seen for all tested strains, while the NPD catheter surfaces showed reduced biofilm formation.

CONCLUSIONS

Modifications of the hydrodynamic characteristics of a catheter can significantly reduce bacterial colonization. Integrated design approaches combining chemical, mechanical and topographical elements can help to reduce the occurrence of CAUTI.

Synthesis of Cyclohepta[b]indoles by (4 + 3) Cycloaddition of 2-Vinylindoles or 4H-Furo[3,2-b]indoles with Oxyallyl Cations

The synthesis of cyclohepta[b]indole derivatives through the dearomative (4 + 3) cycloaddition reaction of 2-vinylindoles or 4H-furo[3,2-b]indoles with in situ generated oxyallyl cations is reported. Oxyallyl cations are generated from α-bromoketones in the presence of a base and a perfluorinated solvent. Cyclohepta[b]indole scaffolds are obtained under mild reaction conditions, in the absence of expensive catalysts, starting from simple reagents, in good to excellent yields and with complete diasteroselectivity. Preliminary expansion of the scope to 3-vinylindoles and to aza-oxyallyl cations is reported.

Efficient parametric generation in a nonlinear photonic crystal pumped by a dual beam

We investigate parametric down-conversion in a hexagonally poled nonlinear photonic crystal, pumped by a dual pump with a transverse modulation that matches the periodicity of the χ ⁽²⁾ nonlinear grating. A peculiar feature of this resonant configuration is that the two pumps simultaneously generate photon pairs over an entire branch of modes, via quasi-phase matching with both fundamental vectors of the reciprocal lattice of the nonlinearity. The parametric gain of these modes depends thus coherently on the sum of the two pump amplitudes and can be controlled by varying their relative intensities and phases. We find that a significant enhancement of the source conversion efficiency, comparable to that of one-dimensionally poled crystals, can be achieved by a dual symmetric pump. We also show how the four-mode coupling arising among shared modes at resonance can be tailored by changing the dual pump parameters.

Integrative and comparative genomic analyses identify clinically relevant pulmonary carcinoid groups and unveil the supra-carcinoids

The worldwide incidence of pulmonary carcinoids is increasing, but little is known about their molecular characteristics. Through machine learning and multi-omics factor analysis, we compare and contrast the genomic profiles of 116 pulmonary carcinoids (including 35 atypical), 75 large-cell neuroendocrine carcinomas (LCNEC), and 66 small-cell lung cancers. Here we report that the integrative analyses on 257 lung neuroendocrine neoplasms stratify atypical carcinoids into two prognostic groups with a 10-year overall survival of 88% and 27%, respectively. We identify therapeutically relevant molecular groups of pulmonary carcinoids, suggesting DLL3 and the immune system as candidate therapeutic targets; we confirm the value of OTP expression levels for the prognosis and diagnosis of these diseases, and we unveil the group of supra-carcinoids. This group comprises samples with carcinoid-like morphology yet the molecular and clinical features of the deadly LCNEC, further supporting the previously proposed molecular link between the low- and high-grade lung neuroendocrine neoplasms.

Gold-Catalyzed Cascade Reactions of 4 H-Furo[3,2- b]indoles with Allenamides: Synthesis of Indolin-3-one Derivatives

Merging the ability of cationic gold(I) catalysts to activate unsaturated π-systems with the electrophiles-driven ring-opening reactions of furans, we describe a new approach to synthesize 2-spiroindolin-3-ones from 4 H-furo[3,2- b]indoles. The reaction occurs through a cascade sequence involving addition of a gold-activated allene to the furan moiety of the starting furoindole followed by a ring-opening/ring-closing event affording 2-spirocyclopentane-1,2-dihydro-3 H-indolin-3-ones in moderate to good yields.

Gold-catalyzed cascade reactions of 4H-furo[3,2-b]indoles with propargyl esters: synthesis of 2-alkenylidene-3-oxoindolines

2-Trienyliden-indolin-3-ones were synthesised in high yields via a gold catalysed cascade reaction between 4H-furo[3,2-b]indoles and propargyl esters.

DnaA and LexA Proteins Regulate Transcription of the uvrB Gene in Escherichia coli: The Role of DnaA in the Control of the SOS Regulon

The uvrB gene belongs to the SOS network, encoding a key component of the nucleotide excision repair. The uvrB promoter region contains three identified promoters with four LexA binding sites, one consensus and six potential DnaA binding sites. A more than threefold increase in transcription of the chromosomal uvrB gene is observed in both the ΔlexA ΔsulA cells and dnaA_A345S cells, and a fivefold increase in the ΔlexA ΔsulA dnaA_A345S cells relative to the wild-type cells. The full activity of the uvrB promoter region requires both the uvrBp1-2 and uvrBp3 promoters and is repressed by both the DnaA and LexA proteins. LexA binds tightly to LexA-box1 at the uvrBp1-2 promoter irrespective of the presence of DnaA and this binding is important for the control of the uvrBp1-2 promoter. DnaA and LexA, however, compete for binding to and regulation of the uvrBp3 promoter in which the DnaA-box6 overlaps with LexA-box4. The transcription control of uvrBp3 largely depends on DnaA-box6. Transcription of other SOS regulon genes, such as recN and dinJ, is also repressed by both DnaA and LexA. Interestingly, the absence of LexA in the presence of the DnaA_A345S mutant leads to production of elongated cells with incomplete replication, aberrant nucleoids and slow growth. We propose that DnaA is a modulator for maintenance of genome integrity during the SOS response by limiting the expression of the SOS regulon.

PD-L1 protein expression assessed by immunohistochemistry is neither prognostic nor predictive of benefit from adjuvant chemotherapy in resected non-small cell lung cancer

Background

The expression of programmed death (PD) ligand 1 (PD-L1) protein expression assessed by immunohistochemistry (IHC) has been correlated with response and survival benefit from anti-PD-1/PD-L1 immune checkpoint inhibitor therapies in advanced non-small cell lung carcinoma (NSCLC). The efficacy of several agents appears correlated with PD-L1 expression. It remains controversial whether PD-L1 is prognostic in NSCLC. We assessed the prognostic value of PD-L1 IHC and its predictive role for adjuvant chemotherapy in early stage NSCLC.

Patients and methods

Tumor sections from three pivotal adjuvant chemotherapy trials (IALT, JBR.10, CALGB 9633) using the E1L3N antibody were studied in this pooled analysis. PD-L1 staining intensity and percentage in both tumor cells (TCs) and immune cells (ICs) were scored by two pathologists. The average or consensus PD-L1 expression levels across intensities and/or percent cells stained were correlated with clinicopathological and molecular features, patient survivals and potential benefit of adjuvant chemotherapy.

Results

Results from 982 patients were available for analysis. Considering staining at any intensities for overall PD-L1 expression, 314 (32.0%), 204 (20.8%) and 141 (14.3%) tumor samples were positive for PD-L1 staining on TCs using cut-offs at ≥1%, ≥10% and ≥25%, respectively. For PD-L1 expressing ICs, 380 (38.7%), 308 (31.4%) and 148 (15.1%) were positive at ≥ 1%, ≥10% and 25% cut-offs, respectively. Positive PD-L1 was correlated with squamous histology, intense lymphocytic infiltrate, and KRAS but not with TP53 mutation. EGFR mutated tumors showed statistically non-significant lower PD-L1 expression. PD-L1 expression was neither prognostic with these cut-offs nor other exploratory cut-offs, nor were predictive for survival benefit from adjuvant chemotherapy.

Conclusions

PD-L1 IHC is not a prognostic factor in early stage NSCLC patients. It is also not predictive for adjuvant chemotherapy benefit in these patients.

Lung adenocarcinomas: correlation of computed tomography and pathology findings

Adenocarcinoma is the most common histologic type of lung cancer. Recent lung adenocarcinoma classifications from the International Association for the Study of Lung cancer, the American Thoracic Society and the European Respiratory Society (IASLC/ETS/ERS, 2011) and World Health Organization (WHO, 2015) define a wide range of adenocarcinoma types and subtypes featuring different prognosis and management. This spectrum of lesions translates into various CT presentations and features, which generally show good correlation with histopathology, stressing the key role of the radiologist in the diagnosis and management of those patients. This review aims at helping radiologists to understand the basics of the up-to-date adenocarcinoma pathological classifications, radio-pathological correlations and how to use them in the clinical setting, as well as other imaging-related correlations (radiogenomics, quantitative analysis, PET-CT).

Influence of Light-curing Parameters on Biofilm Development and Flexural Strength of a Silorane-based Composite

Objectives: The aim of this study was to evaluate the differences in biological and mechanical performances of a silorane-based and a methacrylate-based composite. Another aim was to assess the influence of light-curing time and light-curing intensity on in vitro biofilm formation and flexural strength of the two tested composites.

Methods: Experiment 1: 432 specimens obtained from a silorane-based composite and from a standard methacrylate-based composite were divided into six groups and light-cured for 10, 20, 30, 40, 60, or 80 seconds, using one of two light-curing intensities, 400 mW/cm2 or 800 mW/cm2. At 24 hours, a monospecific Streptococcus mutans biofilm adherent to the surfaces of the samples was obtained. Then, a colorimetric technique (MTT assay) was used to evaluate the adherent viable biomass. Two samples per group were observed using confocal laser scanning microscopy. Analysis of variance (ANOVA) and Tukey tests were used to analyze the results (p&lt;0.05). Experiment 2: 192 bar-shaped specimens were obtained and light-cured as in the previous experiment. A three-point bend test using a universal testing machine was performed to obtain flexural strength values. ANOVA and Tukey tests were used to analyze the results (p&lt;0.05).

Results: In experiment 1, a highly significant difference (p&lt;0.0001) in biofilm development was shown between silorane-based and methacrylate-based composites. In fact, the silorane-based composite exhibited better biological performance. Significant differences were also found between the two light-curing intensities (p&lt;0.018) and for curing times (p&lt;0.0001): silorane-based composite light-cured for 80 seconds at 800 mW/cm2 light-curing intensity showed the lowest biofilm development. In experiment 2, a significant difference in flexural strength (p&lt;0.0318) was only found between the different composites. Nevertheless, both resin composites showed flexural strength values in accordance with International Organization for Standardization guidelines even after 10 seconds of light-curing time.

Conclusions: Silorane-based composite was less prone to biofilm development compared with a methacrylate-based composite. Acceptable flexural strength values for both composites were obtained after 10 seconds of light-curing time.