Amide containing NBTI antibacterials with reduced hERG inhibition, retained antimicrobial activity against gram-positive bacteria and in vivo efficacy.

Novel bacterial topoisomerase inhibitors (NBTIs) are new promising antimicrobials for the treatment of multidrug-resistant bacterial infections. In recent years, many new NBTIs have been discovered, however most of them struggle with the same issue - the balance between antibacterial activity and hERG-related toxicity. We started a new campaign by optimizing the previous series of NBTIs, followed by the design and synthesis of a new, amide-containing focused NBTI library to reduce hERG inhibition and maintain antibacterial activity against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). This optimization strategy yielded the lead compound 12 that exhibits potent antibacterial activity against Gram-positive bacteria, reduced hERG inhibition, no cardiotoxicity in zebrafish model, and a favorable in vivo efficacy in a neutropenic murine thigh infection model of MRSA infection.

Comprehensive investigation of hepatotoxicity of the mixture containing phthalates and bisphenol A.

Connections between the mixture containing bis(2- ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP) and bisphenol A (BPA) and liver injury were explored through in silico investigation and 2 in vivo models. Comparative Toxicogenomics Database (CTD), ShinyGO, ToppCluster and Cytoscape were used for bioinformatic analysis. In vivo subacute study was performed on rats - five groups (n = 6): (1) Control: corn oil, (2) DEHP: 50 mg/kg b.w./day, (3) DBP: 50 mg/kg b.w./day, (4) BPA: 25 mg/kg b.w./day, (5) MIX: DEHP + DBP + BPA. Zebrafish embryos were exposed to the investigated substances in different doses, singularly and combined (binary and ternary mixtures). Liver injury was linked to 75 DEHP, DBP, and BPA genes, mostly connected to inflammation/oxidative stress. In rats, significant alterations in redox status/bioelements and pathohistology were most notable or exclusively present in MIX (probable additive effects). BPA decreased liver area (LA) index in dose-dependent manner. DEHP (< 2 µg/mL) and DBP (≤ 5 µg/mL) reduced LA values, while their higher doses increased LA index. The effect of DBP in binary mixtures led to a lethal outcome at the two highest concentrations, while the hepatotoxicity of DEHP/DBP/BPA mixture was dictated by BPA (confirmed by the benchmark dose analysis).

Novel Quorum Quenching YtnP Lactonase From Bacillus paralicheniformis Reduces Pseudomonas aeruginosa Virulence and Increases Antibiotic Efficacy in vivo.

Bacterial infections have become increasingly difficult to treat due to the occurrence of antibiotic-resistant strains. A promising strategy to increase the efficacy of therapy is to combine antibacterials with agents that decrease pathogen virulence via the modulation of the quorum sensing (QS). Lactonases inhibit acylated homoserine lactone (AHL)-mediated QS in Gram-negative bacteria, including the leading nosocomial pathogen Pseudomonas aeruginosa. Here we describe the characteristics of heterologously expressed YtnP lactonase from Bacillus paralicheniformis ZP1 (YtnP-ZP1) isolated from agricultural soil using the culture enrichment method. Purified YtnP-ZP1 hydrolyzed different AHLs with preference to substrates with long acyl residues as evaluated in assays with biosensors and HPLC. The enzyme showed good thermostability and activity in a wide temperature range. YtnP-ZP1 in 50 µg mL-1 concentration reduced the amount of P. aeruginosa-produced long-chain AHLs by 85%, while it hydrolyzed 50% of short-chain AHLs. Incubation of P. aeruginosa PAO1 with YtnP-ZP1 reduced its swarming motility and elastolytic activity without bactericidal effect. YtnP-ZP1 caused the inhibition of biofilm formation and disintegration of mature biofilms in P. aeruginosa PAO1 and multiresistant clinical strain BR5H that was visualized by crystal violet staining. The treatment with YtnP-ZP1 in concentrations higher than 25 µg mL-1 improved the survival of P. aeruginosa PAO1-infected zebrafish (Danio rerio), rescuing 80% of embryos, while in combination with tobramycin or gentamicin survival rate increased to 100%. The treatment of P. aeruginosa PAO1 biofilms on infected zebrafish tail wounds with 50 µg mL-1 YtnP-ZP1 and 2 × MIC tobramycin led to infection clearing in 2 days. The extensive toxicity studies proved YtnP-ZP1 was non-toxic to human cells and zebrafish. In conclusion, novel YtnP-ZP1 lactonase with its effective anti-virulence activity could be used to increase the efficacy of clinically approved antibiotics in clearing both systemic and biofilm-associated P. aeruginosa infections.

Unraveling the anti-virulence potential and antifungal efficacy of 5-aminotetrazoles using the zebrafish model of disseminated candidiasis.

Candida albicans remains the main causal agent of candidiasis, the most common fungal infection with disturbingly high mortality rates worldwide. The limited diversity and efficacy of clinical antifungal drugs, exacerbated by emerging drug resistance, have resulted in the failure of current antifungal therapies. This imposes an urgent demand for the development of innovative strategies for effective eradication of candidal infections. While the existing clinical drugs display fungicidal or fungistatic activity, the strategy specifically targeting C. albicans filamentation, as the most important virulence trait, represents an attractive approach for overcoming the drawbacks related to clinical antifungals. The results acquired in this study revealed the significant potential of 5-aminotetrazoles as a new class of effective and safe anti-virulence agents. Moreover, these novel agents were active when applied both alone and in combination with clinically approved polyenes. Complete prevention of C. albicans morphogenetic yeast-to-hyphae transition was achieved at doses as low as 1.3 µM under conditions mimicking various filamentation-responsive stimuli in the human body, while no cardio- or hepatotoxicity was observed at doses as high as 200 µM. The treatment of C. albicans-infected zebrafish embryos with nystatin alone had low efficacy, while the combination of nystatin and selected 5-aminotetrazoles prevented fungal filamentation, successfully eliminating the infection and rescuing the infected embryos from lethal disseminated candidiasis. In addition, the most potent anti-virulence 5-aminotetrazole prevented C. albicans in developing the resistance to nystatin when applied in combination, keeping the fungus sensitive to the antifungal drug.

Combatting AMR: A molecular approach to the discovery of potent and non-toxic rhenium complexes active against C. albicans-MRSA co-infection.

Antimicrobial resistance (AMR) is a major emerging threat to public health, causing serious issues in the successful prevention and treatment of persistent diseases. While the problem escalates, lack of financial incentive has lead major pharmaceutical companies to interrupt their antibiotic drug discovery programs. The World Health Organisation (WHO) has called for novel solutions outside the traditional development pathway, with emphasis on new classes of active compounds with non-classical mechanisms of action. Metal complexes are an untapped source of antibiotic potential owing to unique modes of action and a wider range of three-dimensional geometries as compared to purely organic compounds. In this study, we present the antimicrobial and antifungal efficacy of a family of rhenium tricarbonyl diimine complexes with varying ligands, charge and lipophilicity. Our study allowed the identification of potent and non-toxic complexes active in vivo against S. aureus infections at MIC doses as low as 300 ng/mL, as well as against C. albicans-MRSA mixed co-infection. The compounds are capable of suppressing the C. albicans morphogenetic yeast-to-hyphal transition, eradicating fungal-S. aureus co-infection, while showing no sign of cardio-, hepato-, hematotoxiciy or teratogenicity.