Naphthyl-Substituted Indole and Pyrrole Carboxylic Acids as Effective Antibiotic Potentiators-Inhibitors of Bacterial Cystathionine γ-Lyase.

Over the past decades, the problem of bacterial resistance to most antibiotics has become a serious threat to patients' survival. Nevertheless, antibiotics of a novel class have not been approved since the 1980s. The development of antibiotic potentiators is an appealing alternative to the challenging process of searching for new antimicrobials. Production of H2S-one of the leading defense mechanisms crucial for bacterial survival-can be influenced by the inhibition of relevant enzymes: bacterial cystathionine γ-lyase (bCSE), bacterial cystathionine ß-synthase (bCBS), or 3-mercaptopyruvate sulfurtransferase (MST). The first one makes the main contribution to H2S generation. Herein, we present data on the synthesis, in silico analyses, and enzymatic and microbiological assays of novel bCSE inhibitors. Combined molecular docking and molecular dynamics analyses revealed a novel binding mode of these ligands to bCSE. Lead compound 2a manifested strong potentiating activity when applied in combination with some commonly used antibiotics against multidrug-resistant Acinetobacter baumannii, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus. The compound was found to have favorable in vitro absorption, distribution, metabolism, excretion, and toxicity parameters. The high effectiveness and safety of compound 2a makes it a promising candidate for enhancing the activity of antibiotics against high-priority pathogens.

Live Biosensors for Ultrahigh-Throughput Screening of Antimicrobial Activity against Gram-Negative Bacteria.

Gram-negative pathogens represent an urgent threat due to their intrinsic and acquired antibiotic resistance. Many recent drug candidates display prominent antimicrobial activity against Gram-positive bacteria being inefficient against Gram-negative pathogens. Ultrahigh-throughput, microfluidics-based screening techniques represent a new paradigm for deep profiling of antibacterial activity and antibiotic discovery. A key stage of this technology is based on single-cell cocultivation of microbiome biodiversity together with reporter fluorescent pathogen in emulsion, followed by the selection of reporter-free droplets using fluorescence-activated cell sorting. Here, a panel of reporter strains of Gram-negative bacteria Escherichia coli was developed to provide live biosensors for precise monitoring of antimicrobial activity. We optimized cell morphology, fluorescent protein, and selected the most efficient promoters for stable, homogeneous, high-level production of green fluorescent protein (GFP) in E. coli. Two alternative strategies based on highly efficient constitutive promoter pJ23119 or T7 promoter leakage enabled sensitive fluorescent detection of bacterial growth and killing. The developed live biosensors were applied for isolating potent E. coli-killing Paenibacillus polymyxa P4 strain by the ultrahigh-throughput screening of soil microbiome. The multi-omics approach revealed antibiotic colistin (polymyxin E) and its biosynthetic gene cluster, mediating antibiotic activity. Live biosensors may be efficiently implemented for antibiotic/probiotic discovery, environmental monitoring, and synthetic biology.

Development of a rapid method for the analysis of trenbolone, nortestosterone, and zeranol in bovine liver using liquid chromatography tandem mass spectrometry.

A rapid liquid chromatography tandem mass spectrometry method has been developed and validated for the determination of α-trenbolone, ß-trenbolone, α-nortestosterone, ß-nortestosterone, zeranol, and taleranol in bovine liver. The impact of liquid-liquid extraction with methyl tert-butyl ether and optimized solid phase extraction on silica cartridges significantly reduced effort and time of sample preparation. Electrospray ionization gives a significant signal increase compared with atmospheric pressure chemical ionization and atmospheric pressure photoionization. The HPLC gradient was optimized to separate isobaric analytes and matrix constituents from the hormone molecules. The optimized time and temperature of enzymatic hydrolysis of conjugated trenbolone was 4 h at 52 °C. The method validated in the range of 0.5-30 µg kg(-1) for α-trenbolone, ß-trenbolone, zeranol, taleranol, and 2-30 µg kg(-1) for α-nortestosterone, ß-nortestosterone. Combined uncertainty of measurements was in the range of 4%-23%. The matrix effect was negligible (1%-5%) for all analytes except of α-nortestosterone (19%). The developed method with changes concerning sample size and hydrolysis was also applied for the analysis of meat, serum, and urine samples. Graphical Abstract Determination of trenbolone, nortestosterone and zeranol in bovine liver.