In vivo fluorescence imaging of bacteriogenic cyanide in the lungs of live mice infected with cystic fibrosis pathogens

Atypical Mycobacterium abscessus BlaRI Ortholog Mediates Regulation of Energy Metabolism but Not β-Lactam Resistance

Mycobacterium abscessus (Mab) is highly drug resistant, and understanding regulation of antibiotic resistance is critical to future antibiotic development. Regulatory mechanisms controlling Mab's β-lactamase (BlaMab) that mediates β-lactam resistance remain unknown. S. aureus encodes a prototypical protease-mediated two-component system BlaRI regulating the β-lactamase BlaZ. BlaR binds extracellular β-lactams, activating an intracellular peptidase domain which cleaves BlaI to derepress blaZ. Mycobacterium tuberculosis (Mtb) encodes homologs of BlaRI (which we will denote as BlaIR to reflect the inverted gene order in mycobacteria) that regulate not only the Mtb β-lactamase, blaC, but also additional genes related to respiration. We identified orthologs of blaIRMtb in Mab and hypothesized that they regulate blaMab. Surprisingly, neither deletion of blaIRMab nor overexpression of only blaIMab altered blaMab expression or β-lactam susceptibility. However, BlaIMab did bind to conserved motifs upstream of several Mab genes involved in respiration, yielding a putative regulon that partially overlapped with BlaIMtb. Prompted by evidence that respiration inhibitors including clofazimine induce the BlaI regulon in Mtb, we found that clofazimine triggers induction of blaIRMab and its downstream regulon. Highlighting an important role for BlaIRMab in adapting to disruptions in energy metabolism, constitutive repression of the BlaIMab regulon rendered Mab highly susceptible to clofazimine. In addition to our unexpected findings that BlaIRMab does not regulate β-lactam resistance, this study highlights the novel role of mycobacterial BlaRI-type regulators in regulating electron transport and respiration.

One-Step Assembly of Fluorescence-Based Cyanide Sensors from Inexpensive, Off-The-Shelf Materials

We report a simple and versatile approach to assemble sensitive and selective fluorescence “turn-on” sensors for cyanide by combining three off-the-shelf materials; namely fluorescent dye, 1-vinyl imidazole polymer, and cupric chloride. The cyanide-sensing species is a non-fluorescent fluorophore-polymer-Cu²⁺ complex; which forms as a result of the imidazole polymer’s ability to bind both fluorophore and fluorescence quencher (Cu²⁺). Cyanide removes Cu²⁺ from these complexes; thereby “turning-on” sensor fluorescence. These sensors are water-soluble and have a detection limit of ~2.5 μM (CN⁻) in water. Our ternary complex-based sensing approach also enables facile emission tuning; we demonstrate the convenient, synthesis-free preparation of blue and green-emitting sensors using distyrylbiphenyl and fluorescein fluorophores, respectively. Furthermore; these ternary complexes are easily immobilized using agarose to create cyanide-sensing hydrogels; which are then used in a simple; novel microdiffusion apparatus to achieve interference-free cyanide analysis of aqueous media. The present study provides an inexpensive approach for portable; interference-free cyanide detection.

Exploring the Interplay of Resistance Nodulation Division Efflux Pumps, AmpC and OprD in Antimicrobial Resistance of Burkholderia cepacia Complex in Clinical Isolates

Aim: This study aimed at investigating the association of gene expression of multidrug efflux pumps (MexA, MexC, MexE, and MexX), the outer membrane porin OprD, and the β-lactamase AmpC with the antimicrobial susceptibility among 44 clinical isolates of Burkholderia cepacia complex (Bcc). Results: Increased expression of ampC gene showed significant association with reduced susceptibility to chloramphenicol. In fact, reduced susceptibility to chloramphenicol was correlated with overexpression of most genes (ampC, mexC, mexE, and mexX) studied here in majority (>95%) of the Bcc isolates. Increased mexA expression showed significant association with reduced susceptibility to β-lactam antimicrobials (ceftazidime, piperacillin-tazobactam, and meropenem) and co-trimoxazole. Reduced susceptibility to meropenem also showed significant correlation with overexpression of mexC and mexX, whereas reduced susceptibility to ceftazidime was also associated with mexE overexpression. Reduced susceptibility to levofloxacin was significantly associated with overexpression of mexX. The involvement of the efflux pumps in levofloxacin and ceftazidime resistance was further inferred from the finding that the efflux pump inhibitor, carbonyl cyanide m-chlorophenylhydrazone reduced minimum inhibitory concentrations for both the antimicrobials. Conclusions: To conclude, this study explored the high-level expression of mexC, mexE, and mexX efflux pumps genes and ampC in the clinical isolates of Bcc, which can be targeted at treating infections caused by Bcc.

Mechanochemical synthesis of fluorescein-based receptor for CN- ion detection in aqueous solution and cigarette smoke residue

A facile green method for the mechanochemical synthesis of Schiff base phenylhydrazono-N-methylene fluorescein (PHMF) with 95% yields has been established. The synthesized receptor assists in the naked-eye detection of CN^- ions in organic and aqueous media, and F^- ions in acetonitrile over a series of anions with a color transfer from colorless to pink. A redshift of 160 nm of PHMF-CN^- complex in the absorbance spectrum and a turn-on response in the fluorescence spectrum were observed, respectively, at λmax 345 to 515 and 519 nm. A strong interaction of PHMF with CN^- and F^- ions forming a 1:3 binding stoichiometry has been noted in this study. In an aqueous medium for CN^- ion, the lower limit of detection (LOD) is defined as 9.204 nM, which is quite better in terms of sensitivity. In addition, PHMF's paper-strip sensor for rapid real-time CN^- ion sensing was found to be sufficiently sensitive to successfully detect CN^- ion in water and a solid state, resulting in a portable device for detecting cyanide ions. In acetonitrile, the receptor's ability to detect CN^- ion in cigarette smoke residue was also satisfactorily achieved. Graphical Abstract.

Copper Complex-Embedded Vesicular Receptor for Selective Detection of Cyanide Ion and Colorimetric Monitoring of Enzymatic Reaction

Detection of environmentally important ion cyanide (CN^-) has been done by a new method involving displacement of both metal and indicator, metal indicator displacement approach (MIDA) on the vesicular interface. Terpyridine unit was selected as the binding site for metal (Cu²⁺), whereas Eosin-Y (EY) was preferred as an indicator. About 150 nm sized nanoscale vesicular ensemble (Lip-1.Cu) has shown good selectivity and sensitivity for CN^- without any interference from other biologically and environmentally important anions. Otherwise, copper complexes are known for the interferences of binding with phosphates and amino acids. The Lip-1.Cu nanoreceptor also has the possibility to be used for real-time colorimetric scanning for the released HCN via enzymatic reactions. Lip-1.Cu has several superiorities over the other reported sensor systems. It has worked in 100% aqueous environment, fast response time with colorimetric monitoring of enzymatic reaction, and low detection limit.

A benzopyrylium–phenothiazine conjugate of a flavylium derivative as a fluorescent chemosensor for cyanide in aqueous media and its bioimaging

A new benzopyrylium–phenothizine conjugate (BP) has been synthesized for CN⁻sensing.

Novel ratiometric turn-on fluorescent probe for selective sensing of cyanide ions, effect of substitution and bio-imaging studies

Novel fluorogenic receptor, S1 senses highly toxic cyanide ions with typical fluorescent enhancement via inhibition of TICT process. Bioimaging of RAW264.7 cells and real sample analysis of cyanide ions in the domestic waste water were demonstrated.

Biomarkers in Paediatric Cystic Fibrosis Lung Disease

Biomarkers in cystic fibrosis are used i. for the measurement of cystic fibrosis transmembrane regulator function in order to diagnose cystic fibrosis, and ii. to assess aspects of lung disease severity (e.g. inflammation, infection). Effective biomarkers can aid disease monitoring and contribute to the development of new therapies. The tests of cystic fibrosis transmembrane regulator function each have unique strengths and weaknesses, and biomarkers of inflammation, infection and tissue destruction have the potential to enhance the management of cystic fibrosis through the early detection of disease processes. The development of biomarkers of cystic fibrosis lung disease, in particular airway inflammation and infection, is influenced by the challenges of obtaining relevant samples from infants and children for whom early detection and treatment of disease might have the greatest long term benefits.

Clinical and in vitro evidence for the antimicrobial therapy in Burkholderia cepacia complex infections

Treatment of infections caused by Burkholderia cepacia complex (Bcc) in cystic fibrosis (CF) patients poses a complex problem. Bcc is multidrug-resistant due to innate and acquired mechanisms of resistance. As CF patients receive multiple courses of antibiotics, susceptibility patterns of strains from CF patients may differ from those noted in strains from non-CF patients. Thus, there was a need for assessing in vitro and clinical data to guide antimicrobial therapy in these patients. A systematic search of literature, followed by extraction and analysis of available information from human and in vitro studies was done. The results of the analysis are used to address various aspects like use of antimicrobials for pulmonary and non-pulmonary infections, use of combination versus monotherapy, early eradication, duration of therapy, route of administration, management of biofilms, development of resistance during therapy, pharmacokinetics-pharmacodynamics correlations, therapy in post-transplant patients and newer drugs in Bcc-infected CF patients.

Fluorescent probes for the detection of cyanide ions in aqueous medium: cellular uptake and assay for β-glucosidase and hydroxynitrile lyase

A chemodosimetric reagent for specific detection of cyanide species and its possible use in imaging applications as well as assay development for important enzymes.

Luminescent probes for the bioimaging of small anionic species in vitro and in vivo

This comprehensive review examines recent developments in the use of fluorescent/luminescent probes for the bioimaging of anionic species. Images in cover art reproduced with permission from ref. 290 and 306.

Cyanide levels found in infected cystic fibrosis sputum inhibit airway ciliary function

We have previously reported cyanide at concentrations of up to 150 μM in the sputum of cystic fibrosis patients infected with Pseudomonas aeruginosa and a negative correlation with lung function. Our aim was to investigate possible mechanisms for this association, focusing on the effect of pathophysiologically relevant cyanide levels on human respiratory cell function. Ciliary beat frequency measurements were performed on nasal brushings and nasal air-liquid interface (ALI) cultures obtained from healthy volunteers and cystic fibrosis patients. Potassium cyanide decreased ciliary beat frequency in healthy nasal brushings (n = 6) after 60 min (150 μM: 47% fall, p<0.0012; 75 μM: 32% fall, p<0.0001). Samples from cystic fibrosis patients (n = 3) showed similar results (150 μM: 55% fall, p = 0.001). Ciliary beat frequency inhibition was not due to loss of cell viability and was reversible. The inhibitory mechanism was independent of ATP levels. KCN also significantly inhibited ciliary beat frequency in ALI cultures, albeit to a lesser extent. Ciliary beat frequency measurements on ALI cultures treated with culture supernatants from P. aeruginosa mutants defective in virulence factor production implicated cyanide as a key component inhibiting the ciliary beat frequency. If cyanide production similarly impairs mucocilliary clearance in vivo, it could explain the link with increased disease severity observed in cystic fibrosis patients with detectable cyanide in their airway.

Evaluation of antibiotic effects on Pseudomonas aeruginosa biofilm using Raman spectroscopy and multivariate analysis

We investigate the mode of action and classification of antibiotic agents (ceftazidime, patulin, and epigallocatechin gallate; EGCG) on Pseudomonas aeruginosa (P. aeruginosa) biofilm using Raman spectroscopy with multivariate analysis, including support vector machine (SVM) and principal component analysis (PCA). This method allows for quantitative, label-free, non-invasive and rapid monitoring of biochemical changes in complex biofilm matrices with high sensitivity and specificity. In this study, the biofilms were grown and treated with various agents in the microfluidic device, and then transferred onto gold-coated substrates for Raman measurement. Here, we show changes in biochemical properties, and this technology can be used to distinguish between changes induced in P. aeruginosa biofilms using three antibiotic agents. The Raman band intensities associated with DNA and proteins were decreased, compared to control biofilms, when the biofilms were treated with antibiotics. Unlike with exposure to ceftazidime and patulin, the Raman spectrum of biofilms exposed to EGCG showed a shift in the spectral position of the CH deformation stretch band from 1313 cm(-1) to 1333 cm(-1), and there was no difference in the band intensity at 1530 cm(-1) (C = C stretching, carotenoids). The PCA-SVM analysis results show that antibiotic-treated biofilms can be detected with high sensitivity of 93.33%, a specificity of 100% and an accuracy of 98.33%. This method also discriminated the three antibiotic agents based on the cellular biochemical and structural changes induced by antibiotics with high sensitivity and specificity of 100%. This study suggests that Raman spectroscopy with PCA-SVM is potentially useful for the rapid identification and classification of clinically-relevant antibiotics of bacteria biofilm. Furthermore, this method could be a powerful approach for the development and screening of new antibiotics.

A novel cyanide-selective colorimetric and fluorescent chemosensor: first molecular security keypad lock based on phosphotungstic acid and CN- inputs

Rhodamine B (RhB) an available dye has been developed as novel and efficient colorimetric and fluorometric chemosensor for cyanide ions in an absolutely aqueous media. The UV-vis absorption and fluorescent emission titrations experiments have been employed to study the sensing process. RhB could act as an efficient "ON-OFF" fluorescent response for phosphotungstic acid (H3PW12O40 or PTA) based on an ion associate process. Also (RhB(+))3 · PTA(3-) could operate as an "OFF-ON" fluorescent sensor for cyanide anions based on a ligand substitution process. It has been identified as highly sensitive probe for CN(-) which responds at 0.3 and 0.04 μmol L(-1) concentration levels by absorption and fluorescent method respectively. Depending upon the sequence of addition of PTA and CN(-) ions into the solution, RhB could be as a molecular security keypad lock with PTA and CN(-) inputs. The ionic inputs to new fluorophore have been mimicked as a superimposed electronic molecular keypad lock. The results were compared successfully (>96%) with the data of a spectrophotometry approved method (EPA 9014-1) for cyanide ions.

A lung segmental model of chronic Pseudomonas infection in sheep

Background

Chronic lung infection with Pseudomonas aeruginosa is a major contributor to morbidity, mortality and premature death in cystic fibrosis. A new paradigm for managing such infections is needed, as are relevant and translatable animal models to identify and test concepts. We sought to improve on limitations associated with existing models of infection in small animals through developing a lung segmental model of chronic Pseudomonas infection in sheep.

Methodology/Principal Findings

Using local lung instillation of P. aeruginosa suspended in agar beads we were able to demonstrate that such infection led to the development of a suppurative, necrotising and pyogranulomatous pneumonia centred on the instilled beads. No overt evidence of organ or systemic compromise was apparent in any animal during the course of infection. Infection persisted in the lungs of individual animals for as long as 66 days after initial instillation. Quantitative microbiology applied to bronchoalveolar lavage fluid derived from infected segments proved an insensitive index of the presence of significant infection in lung tissue (>10⁴ cfu/g).

Conclusions/Significance

The agar bead model of chronic P. aeruginosa lung infection in sheep is a relevant platform to investigate both the pathobiology of such infections as well as novel approaches to their diagnosis and therapy. Particular ethical benefits relate to the model in terms of refining existing approaches by compromising a smaller proportion of the lung with infection and facilitating longitudinal assessment by bronchoscopy, and also potentially reducing animal numbers through facilitating within-animal comparisons of differential therapeutic approaches.

A novel development of dithizone as a dual-analyte colorimetric chemosensor: detection and determination of cyanide and cobalt (II) ions in dimethyl sulfoxide/water media with biological applications

The behavior of dithizone (DTZ), an easily available dye has been studied for the first time in chromogenic sensing of CN(-) as an anionic species and for Co(2+) as a cationic species in DMSO/H2O media. So employing DTZ an efficient colorimetric chemosensor was afforded with a chromogenic selectivity for Co(2+) over other cations with detection limit of 0.04 μmol L(-1). The complex of Co(2+) with DTZ also displayed ability to detect up to 0.43 μmol L(-1) CN(-) (K(+) salts) among other competing anions through a fast response time of less than 30s which is much lower than most recently reported chromogenic probes. The linear dynamic ranges for the determination of Co(2+) and CN(-) were 0.3-4.4 and 3.3-58.6 μmol L(-1) respectively. This method could have potential application in a variety of cases requiring rapid and accurate analysis of Co(2+) and CN(-) for human serum and water samples.

A single-cell perspective on non-growing but metabolically active (NGMA) bacteria

A long-standing and fundamental problem in microbiology is the non-trivial discrimination between live and dead cells. The existence of physically intact and possibly viable bacterial cells that fail to replicate during a more or less protracted period of observation, despite environmental conditions that are ostensibly propitious for growth, has been extensively documented in many different organisms. In clinical settings, non-culturable cells may contribute to non-apparent infections capable of reactivating after months or years of clinical latency, a phenomenon that has been well documented in the specific case of Mycobacterium tuberculosis. The prevalence of these silent but potentially problematic bacterial reservoirs has been highlighted by classical approaches such as limiting culture dilution till extinction of growing cells, followed by resuscitation of apparently "viable but non-culturable" (VBNC) subpopulations. Although these assays are useful to demonstrate the presence of VBNC cells in a population, they are effectively retrospective and are not well suited to the analysis of non-replicating cells per se. Here, we argue that research on a closely related problem, which we shall refer to as the "non-growing but metabolically active" state, is poised to advance rapidly thanks to the recent development of novel technologies and methods for real-time single-cell analysis. In particular, the combination of fluorescent reporter dyes and strains, microfluidic and microelectromechanical systems, and time-lapse fluorescence microscopy offers tremendous and largely untapped potential for future exploration of the physiology of non-replicating cells.

Imaging inflammation: molecular strategies to visualize key components of the inflammatory cascade, from initiation to resolution

Dysregulation of inflammation is central to the pathogenesis of innumerable human diseases. Understanding and tracking the critical events in inflammation are crucial for disease monitoring and pharmacological drug discovery and development. Recent progress in molecular imaging has provided novel insights into spatial associations, molecular events and temporal sequelae in the inflammatory process. While remaining a burgeoning field in pre-clinical research, increasing application in man affords researchers the opportunity to study disease pathogenesis in humans in situ thereby revolutionizing conventional understanding of pathophysiology and potential therapeutic targets. This review provides a description of commonly used molecular imaging modalities, including optical, radionuclide and magnetic resonance imaging, and details key advances and translational opportunities in imaging inflammation from initiation to resolution.

Salicylimine-based fluorescent chemosensor for aluminum ions and application to bioimaging

In this study, an assay to quantify the presence of aluminum ions using a salicylimine-based receptor was developed utilizing turn-on fluorescence enhancement. Upon treatment with aluminum ions, the fluorescence of the sensor was enhanced at 510 nm due to formation of a 1:1 complex between the chemosensor and the aluminum ions at room temperature. As the concentration of Al(3+) was increased, the fluorescence gradually increased. Other metal ions, such as Na(+), Ag(+), K(+), Ca(2+), Mg(2+), Hg(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Pb(2+), Cr(3+), Fe(3+), and In(3+), had no such significant effect on the fluorescence. In addition, we show that the probe could be used to map intracellular Al(3+) distribution in live cells by confocal microscopy.