Phenotypic Differentiation Within the ' Aminoglycoside Resistance Gene Family Suggests a Novel Subtype IV of Contemporary Clinical Relevance.

Background: Whole genome sequencing of clinical bacterial isolates holds promise in predicting their susceptibility to antibiotic therapy, based on a detailed understanding of the phenotypic manifestation of genotypic variation. The ' aminoglycoside acetyltransferase gene family is the most abundant aminoglycoside resistance determinant encountered in clinical practice. A variety of AAC(6') isozymes have been described, suggesting a phenotypic distinction between subtype I, conferring resistance to amikacin (AMK), and subtype II, conferring resistance to gentamicin (GEN) instead.

L-carnitine co-administration prevents colistin-induced mitochondrial permeability transition and reduces the risk of acute kidney injury in mice.

Colistin is a polymyxin antibiotic currently experiencing renewed clinical interest due to its efficacy in the treatment of multidrug resistant (MDR) bacterial infections. The frequent onset of acute dose-dependent kidney injury, with the potential of leading to long-term renal damage, has limited its use and hampered adequate dosing regimens, increasing the risk of suboptimal plasma concentrations during treatment. The mechanism of colistin-induced renal toxicity has been postulated to stem from mitochondrial damage, yet there is no direct evidence of colistin acting as a mitochondrial toxin.

Synthesis and antibacterial action of 3',6'-disubstituted spectinomycins.

Spectinomycin is an aminocyclitol antibiotic with a unique ribosomal binding site. Prior synthetic modifications of spectinomycin have enhanced potency and antibacterial spectrum through addition at the 6'-position to produce trospectomycin and to the 3'-position to produce spectinamides and aminomethyl spectinomycins. This study focused on the design, synthesis, and evaluation of three 3',6'-disubstituted spectinomycin analogs: trospectinamide, N-benzyl linked aminomethyl, and N-ethylene linked aminomethyl trospectomycins.

Apramycin efficacy against carbapenem- and aminoglycoside-resistant Escherichia coli and Klebsiella pneumoniae in murine bloodstream infection models.

Background: The aminoglycoside apramycin has been proposed as a drug candidate for the treatment of critical Gram-negative systemic infections. However, the potential of apramycin in the treatment of drug-resistant bloodstream infections (BSIs) has not yet been assessed.

Methods: The resistance gene annotations of 40 888 blood-culture isolates were analysed.

Experimental Determination of the p Values of Clinically Relevant Aminoglycoside Antibiotics: Toward Establishing p-Activity Relationships.

Investigating the relationship between individual p values and the efficacy of aminoglycosides is essential for the development of more effective and targeted therapies. In this work, we measured the p values for individual amino groups of the six clinically relevant aminoglycoside antibiotics gentamicin, tobramycin, amikacin, arbekacin, plazomicin, and apramycin using N-H heteronuclear multiple-bond correlation and H NMR experiments. For arbekacin and plazomicin, the p values are reported for the first time.

Phenotypic and genotypic characterization of isolates among individuals at high risk for sexually transmitted diseases in Zurich, Switzerland.

Background: While ceftriaxone resistance remains scarce in Switzerland, global (NG) antimicrobial resistance poses an urgent threat. This study describes clinical characteristics in MSM (men who have sex with men) diagnosed with NG infection and analyses NG resistance by phenotypic and genotypic means.

Methods: Data of MSM enrolled in three clinical cohorts with a positive polymerase chain reaction test (PCR) for NG were analysed between January 2019 and December 2021 and linked with antibiotic susceptibility testing.

Site-Selective Palladium-catalyzed Oxidation of Unprotected Aminoglycosides and Sugar Phosphates.

The site-selective modification of complex biomolecules by transition metal-catalysis is highly warranted, but often thwarted by the presence of Lewis basic functional groups. This study demonstrates that protonation of amines and phosphates in carbohydrates circumvents catalyst inhibition in palladium-catalyzed site-selective oxidation. Both aminoglycosides and sugar phosphates, compound classes that up till now largely escaped direct modification, are oxidized with good efficiency.

Comparison of Disk Diffusion, E-Test, and Broth Microdilution Methods for Testing In Vitro Activity of Cefiderocol in .

The reference method for cefiderocol antimicrobial susceptibility testing is broth microdilution (BMD) with iron-depleted-Mueller-Hinton (ID-MH) medium, whereas breakpoints recommended for disk diffusion (DD) are based on MH-agar plates. We aimed to compare the performance of the commercial BMD tests ComASP (Liofilchem) and UMIC (Bruker), and DD and E-test using MH- and ID-MH-agar plates with the reference BMD method using 100 carbapenem-resistant- isolates. Standard BMD was performed according to the EUCAST guidelines; DD and E-test were carried out using two commercial MH-agar plates (BioMérieux and Liofilchem) and an in-house ID-MH-agar plate, while ComASP and UMIC were performed according to the manufacturer's guidelines.

Synthesis of Gentamicins C1, C2, and C2a and Antiribosomal and Antibacterial Activity of Gentamicins B1, C1, C1a, C2, C2a, C2b, and X2.

Complementing our earlier syntheses of the gentamicins B1, C1a, C2b, and X2, we describe the synthesis of gentamicins C1, C2, and C2a characterized by methyl substitution at the 6'-position, and so present an alternative access to previous chromatographic methods for accessing these sought-after compounds. We describe the antiribosomal activity of our full set of synthetic gentamicin congeners against bacterial ribosomes and hybrid ribosomes carrying the decoding A site of the human mitochondrial, A1555G mutant mitochondrial, and cytoplasmic ribosomes and establish structure-activity relationships with the substitution pattern around ring I to antiribosomal activity, antibacterial resistance due to the presence of aminoglycoside acetyl transferases acting on the 6'-position in ring I, and literature cochlear toxicity data.

Synthesis of 4--(4-Amino-4-deoxy-β-D-xylopyranosyl)paromomycin and 4--(β-D-Xylopyranosyl)-4-deoxy-4'-thio-paromomycin and Evaluation of their Antiribosomal and Antibacterial Activity.

The design, synthesis and antiribosomal and antibacterial activity of two novel glycosides of the aminoglycoside antibiotic paromomycin are described. The first carries of 4-amino-4-deoxy-β-D-xylopyranosyl moiety at the paromomycin 4'-position and is approximately two-fold more active than the corresponding β-D-xylopyranosyl derivative. The second is a 4'-(β-D-xylopyranosylthio) derivative of 4'-deoxyparomomycin that is unexpectedly less active than the simple β-D-xylopyranosyl derivative, perhaps because of the insertion of the conformationally more mobile thioglycosidic linkage.

Synthesis, Antibacterial and Antiribosomal Activity of the 3-Aminoalkyl Modification in the Ribofuranosyl Ring of Apralogs (5--Ribofuranosyl Apramycins).

The synthesis and antiribosomal and antibacterial activity of both anomers of a novel apralog, 5--(5-amino-3--dimethylaminopropyl-D-ribofuranosyl)apramycin, are reported. Both anomers show excellent activity for the inhibition of bacterial ribosomes and that of MRSA and various wild-type Gram negative pathogens. The new compounds retain activity in the presence of the aminoglycoside phosphoryltransferase aminoglycoside modifying enzymes that act on the primary hydroxy group of typical 4,5-(2-deoxystreptamine)-type aminoglycoside and related apramycin derivatives.

Importance of Co-operative Hydrogen Bonding in the Apramycin-Ribosomal Decoding A-Site Interaction.

An intramolecular hydrogen bond between the protonated equatorial 7'-methylamino group of apramycin and the vicinal axial 6'-hydroxy group acidifies the 6'-hydroxy group leading to a strong hydrogen bond to A1408 in the ribosomal drug binding pocket in the decoding A site of the small ribosomal subunit. In 6'-epiapramycin, the trans-nature of the 6'-hydroxy group and the 7'-methylamino group results in a much weaker intramolecular hydrogen bond, and a consequently weaker cooperative hydrogen bonding network with A1408, resulting overall in reduced inhibition of protein synthesis and antibacterial activity.

Apramycin susceptibility of multidrug-resistant Gram-negative blood culture isolates in five countries in Southeast Asia.

Introduction: Bloodstream infections (BSIs) are a leading cause of sepsis, which is a life-threatening condition that significantly contributes to the mortality of bacterial infections. Aminoglycoside antibiotics such as gentamicin or amikacin are essential medicines in the treatment of BSIs, but their clinical efficacy is increasingly being compromised by antimicrobial resistance. The aminoglycoside apramycin has demonstrated preclinical efficacy against aminoglycoside-resistant and multidrug-resistant (MDR) Gram-negative bacilli (GNB) and is currently in clinical development for the treatment of critical systemic infections.

Structure-Activity Relationships for 5'' Modifications of 4,5-Aminoglycoside Antibiotics.

Modification at the 5''-position of 4,5-disubstituted aminoglycoside antibiotics (AGAs) to circumvent inactivation by aminoglycoside modifying enzymes (AMEs) is well known. Such modifications, however, unpredictably impact activity and affect target selectivity thereby hindering drug development. A survey of 5''-modifications of the 4,5-AGAs and the related 5-O-furanosyl apramycin derivatives is presented.

Antibacterial activity of apramycin at acidic pH warrants wide therapeutic window in the treatment of complicated urinary tract infections and acute pyelonephritis.

Background: The clinical-stage drug candidate EBL-1003 (apramycin) represents a distinct new subclass of aminoglycoside antibiotics for the treatment of drug-resistant infections. It has demonstrated best-in-class coverage of resistant isolates, and preclinical efficacy in lung infection models. However, preclinical evidence for its utility in other disease indications has yet to be provided.

Antimicrobial susceptibility patterns of respiratory Gram-negative bacterial isolates from COVID-19 patients in Switzerland.

Background: Bacterial superinfections associated with COVID-19 are common in ventilated ICU patients and impact morbidity and lethality. However, the contribution of antimicrobial resistance to the manifestation of bacterial infections in these patients has yet to be elucidated.

Methods: We collected 70 Gram-negative bacterial strains, isolated from the lower respiratory tract of ventilated COVID-19 patients in Zurich, Switzerland between March and May 2020.

Synthesis and Antibacterial Activity of Propylamycin Derivatives Functionalized at the 5''- and Other Positions with a View to Overcoming Resistance Due to Aminoglycoside Modifying Enzymes.

Propylamycin (4'-deoxy-4'-propylparomomycin) is a next generation aminoglycoside antibiotic that displays increased antibacterial potency over the parent, coupled with reduced susceptibility to resistance determinants and reduced ototoxicity in the guinea pig model. Propylamycin nevertheless is inactivated by APH(3')-Ia, a specific aminoglycoside phosphotransferase isozyme that acts on the primary hydroxy group of the ribofuranosyl moiety (at the 5''-position). To overcome this problem, we have prepared and studied the antibacterial and antiribosomal activity of various propylamycin derivatives carrying amino or substituted amino groups at the 5''-position in place of the vulnerable hydroxy group.

Efficacy of EBL-1003 (apramycin) against Acinetobacter baumannii lung infections in mice.

Objectives: Novel therapeutics are urgently required for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) causing critical infections with high mortality. Here we assessed the therapeutic potential of the clinical-stage drug candidate EBL-1003 (crystalline free base of apramycin) in the treatment of CRAB lung infections.

Methods: The genotypic and phenotypic susceptibility of CRAB clinical isolates to aminoglycosides and colistin was assessed by database mining and broth microdilution.

An Advanced Apralog with Increased in vitro and in vivo Activity toward Gram-negative Pathogens and Reduced ex vivo Cochleotoxicity.

We describe the convergent synthesis of a 5-O-β-D-ribofuranosyl-based apramycin derivative (apralog) that displays significantly improved antibacterial activity over the parent apramycin against wild-type ESKAPE pathogens. In addition, the new apralog retains excellent antibacterial activity in the presence of the only aminoglycoside modifying enzyme (AAC(3)-IV) acting on the parent, without incurring susceptibility to the APH(3') mechanism that disables other 5-O-β-D-ribofuranosyl 2-deoxystreptamine type aminoglycosides by phosphorylation at the ribose 5-position. Consistent with this antibacterial activity, the new apralog has excellent 30 nM activity (IC ) for the inhibition of protein synthesis by the bacterial ribosome in a cell-free translation assay, while retaining the excellent across-the-board selectivity of the parent for inhibition of bacterial over eukaryotic ribosomes.

Predictive Analysis of the Side Chain Conformation of the Higher Carbon Sugars: Application to the Preorganization of the Aminoglycoside Ring 1 Side Chain for Binding to the Bacterial Ribosomal Decoding A Site.

With a view to facilitating prediction of the exocyclic bond to the pyranoside ring in higher carbon sugars, a model is advanced that relates the relative configuration of the three stereogenic centers comprised of the branchpoint and of the two flanking centers (C4-C5-C6 in aldoheptoses and higher and C5-C6-C7 in sialic and ulosonic acids) to that of the simple ring-opened pentoses. Assignment of a given stereotriad as arabino, lxyo, ribo, or xylo by inspection of the Fischer projection formulas permits prediction of conformation of the exocyclic bond by comparison with the known solution (= crystal in all cases) conformations of the simple pentitols. More remote stereogenic centers in the side chain, as in the 8-position of -acetylneuraminic acid, have little impact on the conformation of the exocyclic bond.

Epidemiologic, Phenotypic, and Structural Characterization of Aminoglycoside-Resistance Gene .

Aminoglycoside antibiotics are powerful bactericidal therapeutics that are often used in the treatment of critical Gram-negative systemic infections. The emergence and global spread of antibiotic resistance, however, has compromised the clinical utility of aminoglycosides to an extent similar to that found for all other antibiotic-drug classes. Apramycin, a drug candidate currently in clinical development, was suggested as a next-generation aminoglycoside antibiotic with minimal cross-resistance to all other standard-of-care aminoglycosides.

Apralogs: Apramycin 5--Glycosides and Ethers with Improved Antibacterial Activity and Ribosomal Selectivity and Reduced Susceptibility to the Aminoacyltranserferase (3)-IV Resistance Determinant.

Apramycin is a structurally unique member of the 2-deoxystreptamine class of aminoglycoside antibiotics characterized by a monosubstituted 2-deoxystreptamine ring that carries an unusual bicyclic eight-carbon dialdose moiety. Because of its unusual structure, apramycin is not susceptible to the most prevalent mechanisms of aminoglycoside resistance including the aminoglycoside-modifying enzymes and the ribosomal methyltransferases whose widespread presence severely compromises all aminoglycosides in current clinical practice. These attributes coupled with minimal ototoxocity in animal models combine to make apramycin an excellent starting point for the development of next-generation aminoglycoside antibiotics for the treatment of multidrug-resistant bacterial infections, particularly the ESKAPE pathogens.

Synthesis of saccharocin from apramycin and evaluation of its ribosomal selectivity.

We describe a straightforward synthesis of the apramycin biosynthetic precursor saccharocin from apramycin by regioselective partial azidation followed by stereoretentive oxidative deamination. Saccharocin was found to exhibit excellent selectivity for inhibition of the bacterial ribosome over the eukaryotic ribosomes indicating that its presence as a minor impurity in apramycin itself should not be problematic in the development of the latter as a clinical candidate.