Project description:Macrolides are clinically important antibiotics thought to inhibit bacterial growth by impeding the passage of newly synthesized polypeptides through the nascent peptide exit tunnel of the bacterial ribosome. Recent data challenged this view by showing that macrolide antibiotics can differentially affect synthesis of individual proteins. In order to understand the general mechanism of macrolide action, we used genome-wide ribosome profiling and analyzed the redistribution of ribosomes translating highly expressed genes in bacterial cells treated with high concentrations of macrolide antibiotics. The metagene analysis indicated that inhibition of early rounds of translation, which would be characteristic of the conventional view of macrolide action, occurs only at a limited number of genes. Translation of most genes proceeds past the 5' proximal codons and can be arrested at more distal codons when the ribosome encounters specific short sequence motifs. The sequence motifs enriched in the sites of arrest are confined to the nascent peptide residues in the peptidyl transferase center but not to the peptide segments that contact the antibiotic molecule in the exit tunnel. This led to the conclusion that the general mode of macrolide action involves selective inhibition of peptide bond formation between specific combinations of donor and acceptor substrates. Additional factors operating in the living cell but not during in vitro protein synthesis may modulate site-specific action of macrolide antibiotics.
Project description:BackgroundThe increased risk of cardiovascular events in patients prescribed macrolides has been subject to debate for decades.MethodsMedline, EMBASE databases and ClinicalTrials.gov were searched from inception until August 31, 2022 for studies investigating the link between macrolides and cardiovascular risk. A meta-analysis was performed using a random-effects model.ResultsA total of 80 studies involving 39,374,874 patients were included. No association was found between macrolides and all-cause death. However, compared with the non-macrolide group, macrolides were associated with a significantly increased risk of ventricular arrhythmia or sudden cardiac death (VA or SCD) (azithromycin, relative ratio [RR]: 1.53; 95% confidence interval [CI]: 1.19 to 1.97; clarithromycin, RR: 1.52; 95% CI: 1.07 to 2.16). Besides, administration of macrolides was associated with a higher risk of cardiovascular disease (CVD) death (azithromycin, RR: 1.63; 95% CI: 1.17 to 2.27) and a slightly increased risk of myocardial infarction (MI) (azithromycin, RR: 1.08; 95% CI: 1.02 to 1.15). Interestingly, no association was observed between roxithromycin and adverse cardiac outcomes. Increased risk of VA or SCD was observed for recent or current use of macrolides, MI for former use, and CVD death for current use.ConclusionAdministration of macrolide antibiotics and timing of macrolide use are associated with increased risk for SCD or VTA and cardiovascular death, but not all-cause death.
Project description:Macrolides are clinically important antibiotics thought to inhibit bacterial growth by impeding the passage of newly synthesized polypeptides through the nascent peptide exit tunnel of the bacterial ribosome. Recent data challenged this view by showing that macrolide antibiotics can differentially affect synthesis of individual proteins. In order to understand the general mechanism of macrolide action, we used genome-wide ribosome profiling and analyzed the redistribution of ribosomes translating highly expressed genes in bacterial cells treated with high concentrations of macrolide antibiotics. The metagene analysis indicated that inhibition of early rounds of translation, which would be characteristic of the conventional view of macrolide action, occurs only at a limited number of genes. Translation of most genes proceeds past the 5' proximal codons and can be arrested at more distal codons when the ribosome encounters specific short sequence motifs. The sequence motifs enriched in the sites of arrest are confined to the nascent peptide residues in the peptidyl transferase center but not to the peptide segments that contact the antibiotic molecule in the exit tunnel. This led to the conclusion that the general mode of macrolide action involves selective inhibition of peptide bond formation between specific combinations of donor and acceptor substrates. Additional factors operating in the living cell but not during in vitro protein synthesis may modulate site-specific action of macrolide antibiotics. Comparing ribosome distribution in bacterial cells treated with macrolide antibiotics against the control cells.
Project description:Macrolides, one of the most commonly used class of antibiotics, are a group of drugs produced by Streptomyces species. They belong to the polyketide class of natural products. Their activity is due to the presence of a large macrolide lactone ring with deoxy sugar moieties. They are protein synthesis inhibitors and broad-spectrum antibiotics, active against both gram-positive and gram-negative bacteria. Different analytical techniques have been reported for the determination of macrolides such as chromatographic methods, flow injection methods, spectrofluorometric methods, spectrophotometric methods, and capillary electrophoresis methods. Among these methods, spectrophotometric methods are sensitive and cost effective for the analysis of various antibiotics in pharmaceutical formulations as well as biological samples. This article reviews different spectrophotometric methods for the determination of macrolide antibiotics.
Project description:Macrolide resistance mechanisms can be target-based with a change in a 23S ribosomal RNA (rRNA) residue or a mutation in ribosomal protein L4 or L22 affecting the ribosome's interaction with the antibiotic. Alternatively, mono- or dimethylation of A2058 in domain V of the 23S rRNA by an acquired rRNA methyltransferase, the product of an erm (erythromycin ribosome methylation) gene, can interfere with antibiotic binding. Acquired genes encoding efflux pumps, most predominantly mef(A) + msr(D) in pneumococci/streptococci and msr(A/B) in staphylococci, also mediate resistance. Drug-inactivating mechanisms include phosphorylation of the 2'-hydroxyl of the amino sugar found at position C5 by phosphotransferases and hydrolysis of the macrocyclic lactone by esterases. These acquired genes are regulated by either translation or transcription attenuation, largely because cells are less fit when these genes, especially the rRNA methyltransferases, are highly induced or constitutively expressed. The induction of gene expression is cleverly tied to the mechanism of action of macrolides, relying on antibiotic-bound ribosomes stalled at specific sequences of nascent polypeptides to promote transcription or translation of downstream sequences.
Project description:The chemical modification of structurally complex fermentation products, a process known as semisynthesis, has been an important tool in the discovery and manufacture of antibiotics for the treatment of various infectious diseases. However, many of the therapeutics obtained in this way are no longer effective, because bacterial resistance to these compounds has developed. Here we present a practical, fully synthetic route to macrolide antibiotics by the convergent assembly of simple chemical building blocks, enabling the synthesis of diverse structures not accessible by traditional semisynthetic approaches. More than 300 new macrolide antibiotic candidates, as well as the clinical candidate solithromycin, have been synthesized using our convergent approach. Evaluation of these compounds against a panel of pathogenic bacteria revealed that the majority of these structures had antibiotic activity, some efficacious against strains resistant to macrolides in current use. The chemistry we describe here provides a platform for the discovery of new macrolide antibiotics and may also serve as the basis for their manufacture.
Project description:ObjectivesTo determine the rate, etiology, and timing of unplanned and planned hospital readmissions and to identify risk factors for unplanned readmission in children who survive a hospitalization for trauma.DesignMulticenter retrospective cohort study of a probabilistically linked dataset from the National Trauma Data Bank and the Pediatric Health Information System database, 2007-2012.SettingTwenty-nine U.S. children's hospitals.Patients51,591 children (< 18 yr at admission) who survived more than or equal to a 2-day hospitalization for trauma.Measurements and main resultsThe primary outcome was unplanned readmission within 1 year of discharge from the injury hospitalization. Secondary outcomes included any readmission, reason for readmission, time to readmission, and number of readmissions within 1 year of discharge. The primary exposure groups were isolated traumatic brain injury, both traumatic brain injury and other injury, or nontraumatic brain injury only. We hypothesized a priori that any traumatic brain injury would be associated with both planned and unplanned hospital readmission. We used All Patient Refined Diagnosis Related Groups codes to categorize readmissions by etiology and planned or unplanned. Overall, 4,301/49,982 of the patients (8.6%) with more than or equal to 1 year of observation time were readmitted to the same hospital within 1 year. Many readmissions were unplanned: 2,704/49,982 (5.4%) experienced an unplanned readmission in the first year. The most common reason for unplanned readmission was infection (22%), primarily postoperative or posttraumatic infection (38% of readmissions for infection). Traumatic brain injury was associated with lower odds of unplanned readmission in multivariable analyses. Seizure or RBC transfusion during the index hospitalization were the strongest predictors of unplanned, earlier, and multiple readmissions.ConclusionsMany survivors of pediatric trauma experience unplanned, and potentially preventable, hospital readmissions in the year after discharge. Identification of those at highest risk of readmission can guide targeted in-hospital or postdischarge interventions.