Recent advances in technologies for developing drugs against Chlamydia pneumoniae

Peer reviewe

Exploration of Microbial Communities Using the Thermo Scientific Varioskan LUX Multimode Reader and the Invitrogen EVOS FL Cell Imaging System

Non peer reviewe

Prevention of Staphylococcus aureus biofilm formation by antibiotics in 96-Microtiter Well Plates and Drip Flow Reactors : critical factors influencing outcomes

Biofilm formation leads to the failure of antimicrobial therapy. Thus, biofilm prevention is a desirable goal of antimicrobial research. In this study, the efficacy of antibiotics (doxycycline, oxacillin and rifampicin) in preventing Staphylococcus aureus biofilms was investigated using Microtiter Well Plates (MWP) and Drip Flow Reactors (DFR), two models characterized by the absence and the presence of a continuous flow of nutrients, respectively. Planktonic culture of S. aureus was exposed to antibiotics for one hour followed by 24 hours incubation with fresh nutrients in MWP or continuous flow of nutrients in DFR. The DFR grown biofilms were significantly more tolerant to the antibiotics than those grown in MWP without the continuous flow. The differences in log reductions (LR) between the two models could not be attributed to differences in the cell density, the planktonic inoculum concentration or the surface-area-to-volume ratios. However, eliminating the flow in the DFR significantly restored the antibiotic susceptibility. These findings demonstrate the importance of considering differences between experimental conditions in different model systems, particularly the flow of nutrients, when performing anti-biofilm efficacy evaluations. Biofilm antibiotic efficacy studies should be assessed using various models and more importantly, in a model mimicking conditions of its clinical application.Peer reviewe

(+)-Dehydroabietic Acid, an Abietane-Type Diterpene, Inhibits Staphylococcus aureus Biofilms in Vitro

Peer reviewe

Flavones as Quorum Sensing Inhibitors Identified by a Newly Optimized Screening Platform Using Chromobacterium violaceum as Reporter Bacteria

Quorum sensing (QS) is the process by which bacteria produce and detect signal molecules to coordinate their collective behavior. This intercellular communication is a relevant target for anti-biofilm therapies. Here we have optimized a screening-applicable assay to search for new quorum sensing inhibitors from natural compound libraries. In this system, QS is correlated with the production of violacein, which is directly controlled by the LuxI/LuxR system in Chromobacterium violaceum ATCC 31532. The parallel use of C. violaceum Tn5-mutant CV026, which depends on auto-inducer addition, allows simultaneous discrimination of compounds that act as quenchers of the AHL signal (quorum quenchers). The incorporation of a redox stain into the platform allowed further distinction between QS inhibitors, quorum quenchers and antibacterial compounds. A pilot screening was performed with 465 natural and synthetic flavonoids. All the most active compounds were flavones and they displayed potencies (IC50) in the range of 3.69 to 23.35 M. These leads were particularly promising as they inhibited the transition from microcolonies into mature biofilms from Escherichia coli and Pseudomonas aeruginosa strains. This approach can be very effective in identifying new antimicrobials posing lesser risks of resistance.Peer reviewe

Amphipathic beta(2,2)-Amino Acid Derivatives Suppress Infectivity and Disrupt the Intracellular Replication Cycle of Chlamydia pneumoniae

We demonstrate in the current work that small cationic antimicrobial beta(2,2)-amino acid derivatives (Mw <500 Da) are highly potent against Chlamydia pneumoniae at clinical relevant concentrations (<5 mu M, i.e. <3.4 mu g/mL). C. pneumoniae is an atypical respiratory pathogen associated with frequent treatment failures and persistent infections. This gram-negative bacterium has a biphasic life cycle as infectious elementary bodies and proliferating reticulate bodies, and efficient treatment is challenging because of its long and obligate intracellular replication cycle within specialized inclusion vacuoles. Chlamydicidal effect of the beta(2,2)-amino acid derivatives in infected human epithelial cells was confirmed by transmission electron microscopy. Images of infected host cells treated with our lead derivative A2 revealed affected chlamydial inclusion vacuoles 24 hours post infection. Only remnants of elementary and reticulate bodies were detected at later time points. Neither the EM studies nor resazurin-based cell viability assays showed toxic effects on uninfected host cells or cell organelles after A2 treatment. Besides the effects on early intracellular inclusion vacuoles, the ability of these beta(2,2)-amino acid derivatives to suppress Chlamydia pneumoniae infectivity upon treatment of elementary bodies suggested also a direct interaction with bacterial membranes. Synthetic beta(2,2)-amino acid derivatives that target C. pneumoniae represent promising lead molecules for development of antimicrobial agents against this hard-totreat intracellular pathogen.Peer reviewe

Online measurements of real-time cytotoxic responses induced by multi-component matrices, such as natural products, through electric-cell substrate impedance sensing (ECIS).

Natural products are complex matrices of compounds that are prone to interfere with the label-dependent methods that are typically used for cytotoxicity screenings. Here, we developed a label-free Electric Cell-substrate Impedance Sensing (ECIS)-based cytotoxicity assay that can be applied in the assessment of the cytotoxicity of natural extracts. The conditions to measure the impedance using ECIS were first optimized in mice immortalized hypothalamic neurons GT1-7 cells. The performance of four natural extracts when tested using three conventional cytotoxicity assays in GT1-7 cells, was studied. Betula pendula (silver birch tree) was found to interfere with all of the cytotoxicity assays in which labels were applied. The silver birch extract was also proven to be cytotoxic and, thus, served as a proof-of-concept for the use of ECIS. The extract was fractionated and the ECIS method permitted the distinction of specific kinetic patterns of cytotoxicity on the fractions as well as the extract's pure constituents. This study offers evidence that ECIS is an excellent tool for real-time monitoring of the cytotoxicity of complex extracts that are difficult to work with using conventional (label-based) assays. Altogether, it offers a very suitable cytotoxicity-screening assay making the work with natural products less challenging within the drug discovery workflow.Peer reviewe

Prediction of pre-eclampsia and its subtypes in high-risk cohort : hyperglycosylated human chorionic gonadotropin in multivariate models

Background: The proportion of hyperglycosylated human chorionic gonadotropin (hCG-h) to total human chorionic gonadotropin (%hCG-h) during the first trimester is a promising biomarker for prediction of early-onset pre-eclampsia. We wanted to evaluate the performance of clinical risk factors, mean arterial pressure (MAP), %hCG-h, hCG beta, pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PIGF) and mean pulsatility index of the uterine artery (Uta-PI) in the first trimester in predicting pre-eclampsia (PE) and its subtypes early-onset, late-onset, severe and non-severe PE in a high-risk cohort. Methods: We studied a subcohort of 257 high-risk women in the prospectively collected Prediction and Prevention of Pre-eclampsia and Intrauterine Growth Restriction (PREDO) cohort Multivariate logistic regression was used to construct the prediction models. The first model included background variables and MAP. Additionally, biomarkers were included in the second model and mean Uta-PI was included in the third model. All variables that improved the model fit were included at each step. The area under the curve (AUC) was determined for all models. Results: We found that lower levels of serum PIGF concentration were associated with early-onset PE, whereas lower %hCG-h was associated with the late-onset PE. Serum PIGF was lower and hCG beta higher in severe PE, while %hCG-h and serum PAPP-A were lower in non-severe PE. By using multivariate regression analyses the best prediction for all PE was achieved with the third model: AUC was 0.66, and sensitivity 36% at 90% specificity. Third model also gave the highest prediction accuracy for late-onset, severe and non-severe PE: AUC 0.66 with 32% sensitivity, AUC 0.65, 24% sensitivity and AUC 0.60, 22% sensitivity at 90% specificity, respectively. The best prediction for early-onset PE was achieved using the second model: AUC 0.68 and 20% sensitivity at 90% specificity. Conclusions: Although the multivariate models did not meet the requirements to be clinically useful screening tools, our results indicate that the biomarker profile in women with risk factors for PE is different according to the subtype of PE. The heterogeneous nature of PE results in difficulty to find new, clinically useful biomarkers for prediction of PE in early pregnancy in high-risk cohorts.Peer reviewe

Prediction of pre-eclampsia and its subtypes in high-risk cohort : hyperglycosylated human chorionic gonadotropin in multivariate models

Abstract Background The proportion of hyperglycosylated human chorionic gonadotropin (hCG-h) to total human chorionic gonadotropin (%hCG-h) during the first trimester is a promising biomarker for prediction of early-onset pre-eclampsia. We wanted to evaluate the performance of clinical risk factors, mean arterial pressure (MAP), %hCG-h, hCGβ, pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PlGF) and mean pulsatility index of the uterine artery (Uta-PI) in the first trimester in predicting pre-eclampsia (PE) and its subtypes early-onset, late-onset, severe and non-severe PE in a high-risk cohort. Methods We studied a subcohort of 257 high-risk women in the prospectively collected Prediction and Prevention of Pre-eclampsia and Intrauterine Growth Restriction (PREDO) cohort. Multivariate logistic regression was used to construct the prediction models. The first model included background variables and MAP. Additionally, biomarkers were included in the second model and mean Uta-PI was included in the third model. All variables that improved the model fit were included at each step. The area under the curve (AUC) was determined for all models. Results We found that lower levels of serum PlGF concentration were associated with early-onset PE, whereas lower %hCG-h was associated with the late-onset PE. Serum PlGF was lower and hCGβ higher in severe PE, while %hCG-h and serum PAPP-A were lower in non-severe PE. By using multivariate regression analyses the best prediction for all PE was achieved with the third model: AUC was 0.66, and sensitivity 36% at 90% specificity. Third model also gave the highest prediction accuracy for late-onset, severe and non-severe PE: AUC 0.66 with 32% sensitivity, AUC 0.65, 24% sensitivity and AUC 0.60, 22% sensitivity at 90% specificity, respectively. The best prediction for early-onset PE was achieved using the second model: AUC 0.68 and 20% sensitivity at 90% specificity. Conclusions Although the multivariate models did not meet the requirements to be clinically useful screening tools, our results indicate that the biomarker profile in women with risk factors for PE is different according to the subtype of PE. The heterogeneous nature of PE results in difficulty to find new, clinically useful biomarkers for prediction of PE in early pregnancy in high-risk cohorts. Trial registration International Standard Randomised Controlled Trial number ISRCTN14030412 , Date of registration 6/09/2007, retrospectively registered

Inhibitory activity of the isoflavone Biochanin A on intracellular bacteria of genus Chlamydia and initial development of a buccal formulation

Peer reviewe