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With the current spread of clinically relevant multidrug-resistant (MDR) pathogens, insufficient unearthing of new anti-infectives, and the high cost required for approval of new antimicrobial agents, a strong need for getting these agents via more economic and other alternative routes has emerged. With the discovery of the biosynthetic pathways of various antibiotics pointing out the role of each gene/protein in their antibiotic-producing strains, it became apparent that the biosynthetic gene clusters can be manipulated to produce modified antibiotics. This new approach is known as the combinatorial biosynthesis of new antibiotics which can be employed for obtaining novel derivatives of these valuable antibiotics using genetically modified antibiotic-producing strains (pathway engineering). In this review and based on the available biosynthetic gene clusters of the major aminoglycoside antibiotics (AGAs), the possible alterations or modifications that could be done by co-expression of certain gene(s) previously known to be involved in unique biosynthetic steps have been discussed. In this review defined novel examples of modified AGA using this approach were described and the information provided will act as a platform of researchers to get and develop new antibiotics by the antibiotic-producing bacterial strains such as Streptomyces, Micromonospora,...etc. This way, novel antibiotics with new biological activities could be isolated and used in the treatment of infectious diseases conferring resistance to existing antibiotics. [ABSTRACT FROM AUTHOR]

Abstract With the current spread of clinically relevant multidrug-resistant (MDR) pathogens, insufficient unearthing of new anti-infectives, and the high cost required for approval of new antimicrobial agents, a strong need for getting these agents via more economic and other alternative routes has emerged. With the discovery of the biosynthetic pathways of various antibiotics pointing out the role of each gene/protein in their antibiotic-producing strains, it became apparent that the biosynthetic gene clusters can be manipulated to produce modified antibiotics. This new approach is known as the combinatorial biosynthesis of new antibiotics which can be employed for obtaining novel derivatives of these valuable antibiotics using genetically modified antibiotic-producing strains (pathway engineering). In this review and based on the available biosynthetic gene clusters of the major aminoglycoside antibiotics (AGAs), the possible alterations or modifications that could be done by co-expression of certain gene(s) previously known to be involved in unique biosynthetic steps have been discussed. In this review defined novel examples of modified AGA using this approach were described and the information provided will act as a platform of researchers to get and develop new antibiotics by the antibiotic-producing bacterial strains such as Streptomyces, Micromonospora,…etc. This way, novel antibiotics with new biological activities could be isolated and used in the treatment of infectious diseases conferring resistance to existing antibiotics.

Abstract Background Aminoglycosides have been a cornerstone of the treatment of nosocomial infections caused by Pseudomonas aeruginosa for over 80 years. However, escalating emergence of resistance poses a significant challenge. Therefore, this study aimed to investigate the prevailing patterns of aminoglycoside resistance among clinical isolates of P. aeruginosa in Iran; as well as the underlying resistance mechanisms observed in patients referred to Ardabil hospitals. Methods A total of 200 isolates from five hospitals were evaluated. The resistance profiles of P. aeruginosa isolates to tobramycin, amikacin, and netilmicin were determined using the disk diffusion method. The capacity of aminoglycoside-resistant isolates to form biofilms was assessed through a phenotypic assay, and the results were confirmed using the gene amplification technique. The presence of genes associated with aminoglycoside resistance was detected using polymerase chain reaction (PCR). Quantitative reverse transcription PCR (qRT-PCR) was performed to measure the expression levels of genes encoding the MexXY-OprM efflux pump and PhoPQ two-component system (TCS). Results The prevalence of aminoglycoside-resistant P. aeruginosa isolates was 48%, with 94.7% demonstrating multidrug resistance (MDR). All aminoglycoside-resistant P. aeruginosa strains exhibited biofilm-forming capabilities and harbored all the genes associated with biofilm production. Among the nine genes encoding 16S rRNA methylase and aminoglycoside-modifying enzymes, three genes were detected in these isolates: aac(6’)-Ib (85.4%), ant(2’’)-Ia (18.7%), and aph(3’)-VI (3.1%). Additionally, all aminoglycoside-resistant P. aeruginosa isolates carried mexY and phoP genes, although the expression levels of mexY and phoP were 75% and 87.5%, respectively. Conclusion Given the considerably high prevalence of aminoglycoside-resistant P. aeruginosa strains, urgent measures are warranted to transition towards the use of novel aminoglycosides and to uphold vigilant surveillance of resistance patterns.

Abstract Background Ototoxicity is a major side effect of many broadly used aminoglycoside antibiotics (AGs) and no FDA-approved otoprotective drug is available currently. The zebrafish has recently become a valuable model to investigate AG-induced hair cell toxicity and an expanding list of otoprotective compounds that block the uptake of AGs have been identified from zebrafish-based screening; however, it remains to be established whether inhibiting intracellular cell death pathway(s) constitutes an effective strategy to protect against AG-induced ototoxicity. Results We used the zebrafish model as well as in vitro cell-based assays to investigate AG-induced cell death and found that ferroptosis is the dominant type of cell death induced by neomycin. Neomycin stimulates lipid reactive oxygen species (ROS) accumulation through mitochondrial pathway and blocking mitochondrial ferroptosis pathway effectively protects neomycin-induced cell death. We screened an alkaloid natural compound library and identified seven small compounds that protect neomycin-induced ototoxicity by targeting ferroptosis pathway: six of them are radical-trapping agents (RTAs) while the other one (ellipticine) regulates intracellular iron homeostasis, which is essential for the generation of lipid ROS to stimulate ferroptosis. Conclusions Our study demonstrates that blocking intracellular ferroptosis pathway is an alternative strategy to ameliorate neomycin-induced ototoxicity and provides multiple hit compounds for further otoprotective drug development.

Abstract Background Pharmacokinetics of amikacin administered IV to neonatal foals are described, but little data are available regarding the plasma concentrations contributed by concurrent intra‐articular (IA) administration. Hypothesis/Objectives Compare the pharmacokinetics of amikacin when the total dose is administered IV compared to being divided between IV and IA routes of administration in neonatal foals and predict the plasma concentrations from various combined IV and IA dosing regimens. Animals Eight healthy neonatal foals. Methods Foals received 3 amikacin treatment protocols: (1) IV‐only (25 mg/kg q24h IV), (2) concurrent IV and IA (16.7 mg/kg q24h IV and 8.3 mg/kg q24h into 1 tarsocrural joint), and (3) IA‐only (8.3 mg/kg q24h into 1 tarsocrural joint). Protocols were administered for 3 days beginning at 7, 14, and 21 days of age. Plasma concentrations ≥53 μg/mL at 30 minutes were considered therapeutic for isolates with intermediate susceptibility. Results Foal age was a significant variable. The IV‐only protocol met or exceeded the 30‐minute plasma concentrations considered therapeutic (mean μg/mL [95% confidence interval, CI]) in 7‐ to 9‐day‐old (54.0 [52.2‐56.9]), 14‐ to 16‐day‐old (58.1 [55.2‐61.0]), and 21‐ to 23‐day‐old (66.6 [63.7‐69.6]) foals. Concurrent IV and IA protocol did not reach the 30‐minute concentration considered therapeutic in 7‐ to 9‐day‐old foals (46.5 [43.6‐49.4]) but did in 14‐ to 16‐day‐old (62.9 [60.0‐65.8]) and 21‐to 23‐day‐old (62.6 [59.7‐65.6]) foals. Conclusions and Clinical Importance Concurrent IV and IA administration of amikacin produces 30‐minute plasma concentrations considered therapeutic in foals 14 to 23 days old, but concentrations observed in younger foals might be below those considered therapeutic for isolates with intermediate susceptibility to amikacin.

Background: Aminoglycosides have been a cornerstone of the treatment of nosocomial infections caused by Pseudomonas aeruginosa for over 80 years. However, escalating emergence of resistance poses a significant challenge. Therefore, this study aimed to investigate the prevailing patterns of aminoglycoside resistance among clinical isolates of P. aeruginosa in Iran; as well as the underlying resistance mechanisms observed in patients referred to Ardabil hospitals. Methods: A total of 200 isolates from five hospitals were evaluated. The resistance profiles of P. aeruginosa isolates to tobramycin, amikacin, and netilmicin were determined using the disk diffusion method. The capacity of aminoglycoside-resistant isolates to form biofilms was assessed through a phenotypic assay, and the results were confirmed using the gene amplification technique. The presence of genes associated with aminoglycoside resistance was detected using polymerase chain reaction (PCR). Quantitative reverse transcription PCR (qRT-PCR) was performed to measure the expression levels of genes encoding the MexXY-OprM efflux pump and PhoPQ two-component system (TCS). Results: The prevalence of aminoglycoside-resistant P. aeruginosa isolates was 48%, with 94.7% demonstrating multidrug resistance (MDR). All aminoglycoside-resistant P. aeruginosa strains exhibited biofilm-forming capabilities and harbored all the genes associated with biofilm production. Among the nine genes encoding 16S rRNA methylase and aminoglycoside-modifying enzymes, three genes were detected in these isolates: aac(6')-Ib (85.4%), ant(2")-Ia (18.7%), and aph(3')-VI (3.1%). Additionally, all aminoglycoside-resistant P. aeruginosa isolates carried mexY and phoP genes, although the expression levels of mexY and phoP were 75% and 87.5%, respectively. Conclusion: Given the considerably high prevalence of aminoglycoside-resistant P. aeruginosa strains, urgent measures are warranted to transition towards the use of novel aminoglycosides and to uphold vigilant surveillance of resistance patterns. [ABSTRACT FROM AUTHOR]

Background: Ototoxicity is a major side effect of many broadly used aminoglycoside antibiotics (AGs) and no FDA-approved otoprotective drug is available currently. The zebrafish has recently become a valuable model to investigate AG-induced hair cell toxicity and an expanding list of otoprotective compounds that block the uptake of AGs have been identified from zebrafish-based screening; however, it remains to be established whether inhibiting intracellular cell death pathway(s) constitutes an effective strategy to protect against AG-induced ototoxicity. Results: We used the zebrafish model as well as in vitro cell-based assays to investigate AG-induced cell death and found that ferroptosis is the dominant type of cell death induced by neomycin. Neomycin stimulates lipid reactive oxygen species (ROS) accumulation through mitochondrial pathway and blocking mitochondrial ferroptosis pathway effectively protects neomycin-induced cell death. We screened an alkaloid natural compound library and identified seven small compounds that protect neomycin-induced ototoxicity by targeting ferroptosis pathway: six of them are radical-trapping agents (RTAs) while the other one (ellipticine) regulates intracellular iron homeostasis, which is essential for the generation of lipid ROS to stimulate ferroptosis. Conclusions: Our study demonstrates that blocking intracellular ferroptosis pathway is an alternative strategy to ameliorate neomycin-induced ototoxicity and provides multiple hit compounds for further otoprotective drug development. [ABSTRACT FROM AUTHOR]

Rett syndrome (RTT) is a neurodevelopmental disorder resulting from genetic mutations in the methyl CpG binding protein 2 (MeCP2) gene. Specifically, around 35% of RTT patients harbor premature termination codons (PTCs) within the MeCP2 gene due to nonsense mutations. A promising therapeutic avenue for these individuals involves the use of aminoglycosides, which stimulate translational readthrough (TR) by causing stop codons to be interpreted as sense codons. However, the effectiveness of this treatment depends on several factors, including the type of stop codon and the surrounding nucleotides, collectively referred to as the stop codon context (SCC). Here, we develop a high-content reporter system to precisely measure TR efficiency at different SCCs, assess the recovery of the full-length MeCP2 protein, and evaluate its subcellular localization. We have conducted a comprehensive investigation into the intricate relationship between SCC characteristics and TR induction, examining a total of 14 pathogenic MeCP2 nonsense mutations with the aim to advance the prospects of personalized therapy for individuals with RTT. Our results demonstrate that TR induction can successfully restore full-length MeCP2 protein, albeit to varying degrees, contingent upon the SCC and the specific position of the PTC within the MeCP2 mRNA. TR induction can lead to the re-establishment of nuclear localization of MeCP2, indicating the potential restoration of protein functionality. In summary, our findings underscore the significance of SCC-specific approaches in the development of tailored therapies for RTT. By unraveling the relationship between SCC and TR therapy, we pave the way for personalized, individualized treatment strategies that hold promise for improving the lives of individuals affected by this debilitating neurodevelopmental disorder. Key messages: The efficiency of readthrough induction at MeCP2 premature termination codons strongly depends on the stop codon context. The position of the premature termination codon on the transcript influences the readthrough inducibility. A new high-content dual reporter assay facilitates the measurement and prediction of readthrough efficiency of specific nucleotide stop contexts. Readthrough induction results in the recovery of full-length MeCP2 and its re-localization to the nucleus. MeCP2 requires only one of its annotated nuclear localization signals. [ABSTRACT FROM AUTHOR]

Background: Pharmacokinetics of amikacin administered IV to neonatal foals are described, but little data are available regarding the plasma concentrations contributed by concurrent intra‐articular (IA) administration. Hypothesis/Objectives: Compare the pharmacokinetics of amikacin when the total dose is administered IV compared to being divided between IV and IA routes of administration in neonatal foals and predict the plasma concentrations from various combined IV and IA dosing regimens. Animals: Eight healthy neonatal foals. Methods: Foals received 3 amikacin treatment protocols: (1) IV‐only (25 mg/kg q24h IV), (2) concurrent IV and IA (16.7 mg/kg q24h IV and 8.3 mg/kg q24h into 1 tarsocrural joint), and (3) IA‐only (8.3 mg/kg q24h into 1 tarsocrural joint). Protocols were administered for 3 days beginning at 7, 14, and 21 days of age. Plasma concentrations ≥53 μg/mL at 30 minutes were considered therapeutic for isolates with intermediate susceptibility. Results: Foal age was a significant variable. The IV‐only protocol met or exceeded the 30‐minute plasma concentrations considered therapeutic (mean μg/mL [95% confidence interval, CI]) in 7‐ to 9‐day‐old (54.0 [52.2‐56.9]), 14‐ to 16‐day‐old (58.1 [55.2‐61.0]), and 21‐ to 23‐day‐old (66.6 [63.7‐69.6]) foals. Concurrent IV and IA protocol did not reach the 30‐minute concentration considered therapeutic in 7‐ to 9‐day‐old foals (46.5 [43.6‐49.4]) but did in 14‐ to 16‐day‐old (62.9 [60.0‐65.8]) and 21‐to 23‐day‐old (62.6 [59.7‐65.6]) foals. Conclusions and Clinical Importance: Concurrent IV and IA administration of amikacin produces 30‐minute plasma concentrations considered therapeutic in foals 14 to 23 days old, but concentrations observed in younger foals might be below those considered therapeutic for isolates with intermediate susceptibility to amikacin. [ABSTRACT FROM AUTHOR]

Aminoglycoside antibiotics target ribosomes and are effective against a wide range of bacteria. Here, we demonstrated that knockout strains related to energy metabolism in Escherichia coli showed increased tolerance to aminoglycosides during the mid-exponential growth phase. Contrary to expectations, these mutations did not reduce the proton motive force or aminoglycoside uptake, as there were no significant changes in metabolic indicators or intracellular gentamicin levels between wild-type and mutant strains. Our comprehensive proteomics analysis unveiled a noteworthy upregulation of proteins linked to the tricarboxylic acid (TCA) cycle in the mutant strains during the mid-exponential growth phase, suggesting that these strains compensate for the perturbation in their energy metabolism by increasing TCA cycle activity to maintain their membrane potential and ATP levels. Furthermore, our pathway enrichment analysis shed light on local network clusters displaying downregulation across all mutant strains, which were associated with both large and small ribosomal binding proteins, ribosome biogenesis, translation factor activity, and the biosynthesis of ribonucleoside monophosphates. These findings offer a plausible explanation for the observed tolerance of aminoglycosides in the mutant strains. Altogether, this research provides valuable insights into the mechanisms of aminoglycoside tolerance, paving the way for novel strategies to combat such cells.

The occurrence of multidrug-resistant Acinetobacter baumannii (MDRA) has increased rapidly and is associated with severe nosocomial infections. MDRA has emerged in the hospital setting and has evolved into extensively drug-resistant A. baumannii (XDRA). A clinical XDRA isolate obtained from a hospitalised patient in 2016 was evaluated for antibiotic susceptibility and whole-genome sequence. The XDRA isolate was resistant to β-lactams, including broad-spectrum cephalosporins and carbapenems, and to aminoglycosides, fosfomycin, fluoroquinolones, tetracyclines, tigecycline, and trimethoprim-sulfamethoxazole. The isolate harboured abaF, ant(3″)-II-c, aph(3″)-Ib, aph(6)-Id, armA, blaADC-73, blaTEM-1, blaOXA-66, blaOXA-23, mphE, msrE and tet(B). Quinolone resistance was associated with mutations gyrA S81L and parC S84L. Tigecycline resistance was associated with a mutation in adeS. The isolate belonged to Oxford and Pasteur scheme sequence type 1050 and 2, respectively, and harboured a conjugative plasmid containing the aminoglycoside resistance transposon TnaphA6. Our study demonstrates that the isolate is closely related to a recent MDRA identified in Australia and the USA, in which a similar conjugative plasmid is not observed. Although the MDRA in Australia caused an outbreak, our hospital's surveillance protocol managed to prevent a further outbreak. Our finding suggests that this XDRA isolate is of concern in hospital and community care settings. The gpi allele could be a marker for discriminating this isolate from clonal complex 92 isolates.

The occurrence of multidrug-resistant Acinetobacter baumannii (MDRA) has increased rapidly and is associated with severe nosocomial infections. MDRA has emerged in the hospital setting and has evolved into extensively drug-resistant A. baumannii (XDRA). A clinical XDRA isolate obtained from a hospitalised patient in 2016 was evaluated for antibiotic susceptibility and whole-genome sequence. The XDRA isolate was resistant to β-lactams, including broad-spectrum cephalosporins and carbapenems, and to aminoglycosides, fosfomycin, fluoroquinolones, tetracyclines, tigecycline, and trimethoprim-sulfamethoxazole. The isolate harboured abaF , ant(3″)-II-c , aph(3″)-Ib , aph(6)-Id , armA , bla ADC-73 , bla TEM-1 , bla OXA-66 , bla OXA-23 , mphE , msrE and tet(B). Quinolone resistance was associated with mutations gyrA S81L and parC S84L. Tigecycline resistance was associated with a mutation in adeS. The isolate belonged to Oxford and Pasteur scheme sequence type 1050 and 2, respectively, and harboured a conjugative plasmid containing the aminoglycoside resistance transposon Tn aphA6. Our study demonstrates that the isolate is closely related to a recent MDRA identified in Australia and the USA, in which a similar conjugative plasmid is not observed. Although the MDRA in Australia caused an outbreak, our hospital's surveillance protocol managed to prevent a further outbreak. Our finding suggests that this XDRA isolate is of concern in hospital and community care settings. The gpi allele could be a marker for discriminating this isolate from clonal complex 92 isolates. [ABSTRACT FROM AUTHOR]

Abstract Background Sensorineural hearing loss (SNHL) poses a major threat to both physical and mental health; however, there is still a lack of effective drugs to treat the disease. Recently, novel biological therapies, such as mesenchymal stem cells (MSCs) and their products, namely, exosomes, are showing promising therapeutic potential due to their low immunogenicity, few ethical concerns, and easy accessibility. Nevertheless, the precise mechanisms underlying the therapeutic effects of MSC-derived exosomes remain unclear. Results Exosomes derived from MSCs reduced hearing and hair cell loss caused by neomycin-induced damage in models in vivo and in vitro. In addition, MSC-derived exosomes modulated autophagy in hair cells to exert a protective effect. Mechanistically, exogenously administered exosomes were internalized by hair cells and subsequently upregulated endocytic gene expression and endosome formation, ultimately leading to autophagy activation. This increased autophagic activity promoted cell survival, decreased the mitochondrial oxidative stress level and the apoptosis rate in hair cells, and ameliorated neomycin-induced ototoxicity. Conclusions In summary, our findings reveal the otoprotective capacity of exogenous exosome-mediated autophagy activation in hair cells in an endocytosis-dependent manner, suggesting possibilities for deafness treatment.

Background: Sensorineural hearing loss (SNHL) poses a major threat to both physical and mental health; however, there is still a lack of effective drugs to treat the disease. Recently, novel biological therapies, such as mesenchymal stem cells (MSCs) and their products, namely, exosomes, are showing promising therapeutic potential due to their low immunogenicity, few ethical concerns, and easy accessibility. Nevertheless, the precise mechanisms underlying the therapeutic effects of MSC-derived exosomes remain unclear. Results: Exosomes derived from MSCs reduced hearing and hair cell loss caused by neomycin-induced damage in models in vivo and in vitro. In addition, MSC-derived exosomes modulated autophagy in hair cells to exert a protective effect. Mechanistically, exogenously administered exosomes were internalized by hair cells and subsequently upregulated endocytic gene expression and endosome formation, ultimately leading to autophagy activation. This increased autophagic activity promoted cell survival, decreased the mitochondrial oxidative stress level and the apoptosis rate in hair cells, and ameliorated neomycin-induced ototoxicity. Conclusions: In summary, our findings reveal the otoprotective capacity of exogenous exosome-mediated autophagy activation in hair cells in an endocytosis-dependent manner, suggesting possibilities for deafness treatment. [ABSTRACT FROM AUTHOR]

This research focuses on combating the increasing problem of antimicrobial resistance, especially in Escherichia coli (E. coli), by assessing the efficacy of aminoglycosides. The study specifically addresses the challenge of developing new therapeutic approaches by integrating experimental data with mathematical modeling to better understand the action of aminoglycosides. It involves testing various antibiotics like streptomycin (SMN), kanamycin (KMN), gentamicin (GMN), tobramycin (TMN), and amikacin (AKN) against the O157:H7 strain of E. coli. The study employs a pharmacodynamics (PD) model to analyze how different antibiotic concentrations affect bacterial growth, utilizing minimum inhibitory concentration (MIC) to gauge the effective bactericidal levels of the antibiotics. The study's approach involved transforming bacterial growth rates, as obtained from time–kill curve data, into logarithmic values. A model was then developed to correlate these log-transformed values with their respective responses. To generate additional data points, each value was systematically increased by an increment of 0.1. To simulate real-world variability and randomness in the data, a Gaussian scatter model, characterized by parameters like κ and EC50, was employed. The mathematical modeling was pivotal in uncovering the bactericidal properties of these antibiotics, indicating different PD MIC (zMIC) values for each (SMN: 1.22; KMN: 0.89; GMN: 0.21; TMN: 0.32; AKN: 0.13), which aligned with MIC values obtained through microdilution methods. This innovative blend of experimental and mathematical approaches in the study marks a significant advancement in formulating strategies to combat the growing threat of antimicrobial-resistant E. coli, offering a novel pathway to understand and tackle antimicrobial resistance more effectively. [ABSTRACT FROM AUTHOR]

Staphylococcus haemolyticus 010503B is a multidrug-resistant bacterium isolated from an outpatient clinic in a hospital waiting area in Thailand. Here we present the draft genome sequence of S. haemolyticus 010503B. The paired-end reads were generated on the Illumina NextSeq 550 sequencer using genomic DNA from the pure culture of S. haemolyticus 010503B. The draft genome consisted of 114 contigs with a total size of 2,457,654 base pairs, an N50 of 57,312 base pairs and a GC content of 32.60%. The dDDH between 010503B and Staphylococcus haemolyticus SM 131T was 91.9%, identifying the strain as Staphylococcus haemolyticus. The data presented holds promise for bacterial classification, comparative genomics, analysing antimicrobial resistance comprehensively, and assessing bacterial virulence factors of S. haemolyticus. The draft genome sequence data has been deposited at NCBI under Bioproject accession number PRJNA550309.

Background: Pulmonary infections by gram-negative organisms are important in cystic fibrosis (CF). Aminoglycosides (AG) are often part of the treatment regimen. However, they are a well-known cause of ototoxicity. Even minimal hearing impairment in children could have a future impact on functional well-being.We aimed to investigate the progression of sensorineural hearing loss (SNHL) over several years in pediatric CF patients, and to identify risk factors, such as the use of AG, including both intravenous (IV) and inhaled AG. Methods: Retrospective analyses of patient records from children and adolescents followed up at the CF clinic of the Antwerp University Hospital, Belgium, were performed. We collected data on age, sex, pure-tone audiometry, and the use of AG. Descriptive and binary logistic regression analyses, and if indicated generalized estimating equations (GEE) analyses were performed. Results: Forty pediatric patients were enrolled in the study taking part from 2013 to 2020. Pure-tone audiometry revealed an important rate of SNHL over several years, with a prevalence of 29 % for high-frequency SNHL (i.e. 8 kHz). Increasing age was identified as a significant risk factor for the development of SNHL at 8 kHz if 5 or more IV AG courses (p = 0.01) were reported or when IV AG were combined with inhaled AG (p = 0.002). Conclusions: Age combined with the use of IV AG (≥5 courses or in combination with inhaled AG) are predictive for developing high-frequency SNHL (i.e. 8 kHz). We suggest routine annual hearing screening (incl. high-frequency thresholds) in CF patients, starting from childhood.

Amikacin and kanamycin are second-line injectables used in the treatment of multidrug-resistant tuberculosis (MDR-TB) based on the clinical utility of streptomycin, another aminoglycoside and first-line anti-TB drug. While streptomycin was tested as a single agent in the first controlled TB clinical trial, introduction of amikacin and kanamycin into MDR-TB regimens was not preceded by randomized controlled trials. A recent large retrospective meta-analysis revealed that compared with regimens without any injectable drug, amikacin provided modest benefits, and kanamycin was associated with worse outcomes. Although their long-term use can cause irreversible ototoxicity, they remain part of MDR-TB regimens because they have a role in preventing emergence of resistance to other drugs. To quantify the contribution of amikacin and kanamycin to second-line regimens, we applied two-dimensional matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging in large lung lesions, quantified drug exposure in lung and in lesions of rabbits with active TB, and measured the concentrations required to kill or inhibit growth of the resident bacterial populations. Using these metrics, we applied site-of-action pharmacokinetic and pharmacodynamic (PK-PD) concepts and simulated drug coverage in patients' lung lesions. The results provide a pharmacological explanation for the limited clinical utility of both agents and reveal better PK-PD lesion coverage for amikacin than kanamycin, consistent with retrospective data of contribution to treatment success. Together with recent mechanistic studies dissecting antibacterial activity from aminoglycoside ototoxicity, the limited but rapid penetration of streptomycin, amikacin, and kanamycin to the sites of TB disease supports the development of analogs with improved efficacy and tolerability.

Antimicrobial resistance is a critical public health issue that requires a thorough understanding of the factors that influence the selection and spread of antibiotic-resistant bacteria. Biocides, which are widely used in cleaning and disinfection procedures in a variety of settings, may contribute to this resistance by inducing similar defense mechanisms in bacteria against both biocides and antibiotics. However, the strategies used by bacteria to adapt and develop cross-resistance remain poorly understood, particularly within biofilms –a widespread bacterial habitat that significantly influences bacterial tolerance and adaptive strategies. Using a combination of adaptive laboratory evolution experiments, genomic and RT-qPCR analyses, and biofilm structural characterization using confocal microscopy, we investigated in this study how Escherichia coli biofilms adapted after 28 days of exposure to three biocidal active substances and the effects on cross-resistance to antibiotics. Interestingly, polyhexamethylene biguanide (PHMB) exposure led to an increase of gentamicin resistance (GenR) phenotypes in biofilms formed by most of the seven E. coli strains tested. Nevertheless, most variants that emerged under biocidal conditions did not retain the GenR phenotype after removal of antimicrobial stress, suggesting a transient adaptation (adaptive resistance). The whole genome sequencing of variants with stable GenR phenotypes revealed recurrent mutations in genes associated with cellular respiration, including cytochrome oxidase (cydA, cyoC) and ATP synthase (atpG). RT-qPCR analysis revealed an induction of gene expression associated with biofilm matrix production (especially curli synthesis), stress responses, active and passive transport and cell respiration during PHMB exposure, providing insight into potential physiological responses associated with adaptive crossresistance. In addition, confocal laser scanning microscopy (CLSM) observations demonstrated a global effect of PHMB on biofilm architectures and compositions formed by most E. coli strains, with the appearance of dense cellular clusters after a 24h-exposure. In conclusion, our results showed that the PHMB exposure stimulated the emergence of an adaptive cross-resistance to gentamicin in biofilms, likely induced through the activation of physiological responses and biofilm structural modulations altering gradients and microenvironmental conditions in the biological edifice.

Klebsiella pneumoniae are bacteria associated with respiratory tract infections and are increasingly becoming resistant to antibiotics, including carbapenems. Apramycin is a veterinary antibiotic that may have the potential to be re-purposed for use in human health, for example, for the treatment of respiratory tract infections after coupling to inhalable nanoparticles. In the present study, the antibiotic apramycin was formulated with single chain polymeric nanoparticles and tested in free and formulated forms against a set of 13 Klebsiella pneumoniae isolates (from the Netherlands and Pakistan) expressing different aminoglycoside resistance phenotypes. Minimum Inhibitory Concentration, Time Kill Kinetics and biofilm experiments were performed providing evidence for the potential efficacy of apramycin and apramycin-based nanomedicines for the treatment of human Klebsiella pneumonia infections.

In this study, we assess the scattering of light and auto-fluorescence from single bacterial cells to address the challenge of fast (<2  h), label-free phenotypic antimicrobial susceptibility testing (AST). Label-free flow cytometry is used for monitoring both the respiration-related auto-fluorescence in two different fluorescence channels corresponding to FAD and NADH, and the morphological and structural information contained in the light scattered by individual bacteria during incubation with or without antibiotic. Large multi-parameter data are analyzed using dimensionality reduction methods, based either on a combination of 2D binning and Principal Component Analysis, or with a one-class Support Vector Machine approach, with the objective to predict the Susceptible or Resistant phenotype of the strain. For the first time, both Escherichia coli (Gramnegative) and Staphylococcus epidermidis (Gram-positive) isolates were tested with a label-free approach, and, in the presence of two groups of bactericidal antibiotic molecules, aminoglycosides and beta-lactams. Our results support the feasibility of label-free AST in less than 2  h and suggest that single cell autofluorescence adds value to the Susceptible/Resistant phenotyping over singlecell scattering alone, in particular for the mecA+ Staphylococcus (i.e., resistant) strains treated with oxacillin. [ABSTRACT FROM AUTHOR]

Choosing the appropriate antibiotics to treat bacterial infections has grown more challenging as a result of the emergence of antibiotic-resistant bacteria. Aminoglycosides, as broad-spectrum antibiotics, are increasingly being used clinically; however, for most effective employment of aminoglycosides, a comprehensive understanding of aminoglycoside resistance genes’ prevalence and dissemination is required. Therefore, to better understand the global resistance status of aminoglycoside antibiotics and the prevalence of antibiotic-resistance genes (ARGs) in various bacterial species, this systematic review gathered relevant data from multiple studies. Two primary resistance mechanisms—aminoglycoside enzymatic modification and 16S rRNA methylation—were assessed, and the prevalence of the corresponding ARGs was described. The coexistence of aminoglycoside ARGs with other ARGs was also demonstrated, as was the relationship between aminoglycoside ARGs and resistant phenotypes. The lack of effective therapeutic agents to combat resistant pathogens presents a real threat to public health. The combination of aminoglycosides with other antibiotics may provide a novel treatment strategy.

Abstract Background The assumptions of conventional spatial models cannot estimate the responses across space and over time. Here we propose new spatial panel data models to investigate the association between the risk factors and incidence of end-stage renal disease (ESRD). Methods A longitudinal (panel data) study was conducted using data from the National Health Insurance Database in Taiwan. We developed an algorithm to identify the patient’s residence and estimate the ESRD rate in each township. Corresponding covariates, including patient comorbidities, history of medication use, and socio-environmental factors, were collected. Local Indicators of Spatial Association were used to describe local spatial clustering around an individual location. Moreover, a spatial panel data model was proposed to investigate the association between ESRD incidence and risk factors. Results In total, 73,995 patients with ESRD were included in this study. The western region had a higher proportion of high incidence rates than the eastern region. The proportion of high incidence rates in the eastern areas increased over the years. We found that most “social environmental factors,” except average income and air pollution (PM 2.5 and PM10), had a significant influence on the incidence rate of ESRD when considering spatial dependences of response and explanatory variables. Receiving non-steroidal anti-inflammatory drugs and aminoglycosides within 90 days prior to ESRD had a significant positive effect on the ESRD incidence rate. Conclusion Future comprehensive studies on townships located in higher-risk clusters of ESRD will help in designing healthcare policies for suitable action.

G-quadruplex-forming nucleic acids have evolved to have applications in biology, drug design, sensing, and nanotechnology, to name a few. Together with the structural understanding, several attempts have been made to discover and design new classes of chemical agents that target these structures in the hope of using them as future therapeutics. Here, we report the binding of aminoglycosides, in particular neomycin, to parallel G-quadruplexes that exist as G-quadruplex monomers, dimers, or compounds that have the propensity to form dimeric G-quadruplex structures. Using a combination of calorimetric and spectroscopic studies, we show that neomycin binds to the parallel G-quadruplex with affinities in the range of Ka ∼ 105–108 M-1, which depends on the base composition, ability to form dimeric G-quadruplex structures, salt, and pH of the buffer used. At pH 7.0, the binding of neomycin was found to be electrostatically driven potentially through the formation of ion pairs formed with the quadruplex. Lowering the pH resulted in neomycin’s association constants in the range of Ka ∼ 106–107 M-1 in a salt dependent manner. Circular dichroism (CD) studies showed that neomycin’s binding does not cause a change in the parallel conformation of the G-quadruplex, yet some binding-induced changes in the intensity of the CD signals were seen. A comparative binding study of neomycin and paromomycin using d(UG4T) showed paromomycin binding to be much weaker than neomycin, highlighting the importance of ring I in the recognition process. In toto, our results expanded the binding landscape of aminoglycosides where parallel G-quadruplexes have been discovered as one of the high-affinity sites. These results may offer a new understanding of some of the undesirable functions of aminoglycosides and help in the design of aminoglycoside-based G-quadruplex binders of high affinity.

Using cryo-electron microscopy (cryo-EM), we determined the structure of the Escherichia coli 70S ribosome with a global resolution of 2.0 Å. The maps reveal unambiguous positioning of protein and RNA residues, their detailed chemical interactions, and chemical modifications. Notable features include the first examples of isopeptide and thioamide backbone substitutions in ribosomal proteins, the former likely conserved in all domains of life. The maps also reveal extensive solvation of the small (30S) ribosomal subunit, and interactions with A-site and P-site tRNAs, mRNA, and the antibiotic paromomycin. The maps and models of the bacterial ribosome presented here now allow a deeper phylogenetic analysis of ribosomal components including structural conservation to the level of solvation. The high quality of the maps should enable future structural analyses of the chemical basis for translation and aid the development of robust tools for cryo-EM structure modeling and refinement.

Abstract Background The treatment of swine dysentery (SD) has become constrained in recent years due to the limited availability of effective drugs combined with a rise in antimicrobial resistance. Gentamicin, an aminoglycoside antibiotic, is authorised for the control of this disease in several European countries but has not been extensively used so far. In this study, the in vitro susceptibility of 56 Brachyspira hyodysenteriae field isolates was evaluated against gentamicin using a broth microdilution test. The molecular basis of decreased susceptibility to gentamicin was also investigated by sequencing the 16S rRNA gene and phylogenetic relatedness by multiple-locus variable number tandem-repeat analysis (MLVA). Results Most B. hyodysenteriae isolates presented low minimum inhibitory concentration (MIC) values to gentamicin, with a mode of 2 µg/mL, a median or MIC50 of 4 µg/mL and percentile 90 or MIC90 of 16 µg/mL. The distribution of these values over the period studied (2011–2019) did not show a tendency towards the development of resistance to gentamicin. Differences in susceptibility among isolates could be explained by two point-mutations in the 16S rRNA gene, C990T and A1185G, which were only present in isolates with high MICs. These isolates were typed in three different MLVA clusters. Analyses of co-resistance between gentamicin and antimicrobials commonly used for the treatment of SD revealed that resistance to tiamulin and valnemulin was associated with low MICs for gentamicin. Conclusions The results provide an accurate characterisation of antimicrobial sensitivity to gentamicin and possible mechanisms of resistance in Spanish B. hyodysenteriae isolates. These findings allow us to propose gentamicin as an alternative in the antibiotic management of SD, particularly in outbreaks caused by pleuromutilin resistant isolates.

Background: Gentamicin (GNT) is a highly effective aminoglycoside antibiotic that is commonly used to treat life-threatening bacterial infections. Aim: The aim of the current study is to determine whether tadalafil can protect against GNT-induced nephrotoxicity. Methods: Twenty-four male Albino rats were used in the study, which were randomly divided into four groups, six animals each. Control untreated group received distilled water (5ml/kg, P.O) for 12 days and on days 6-12, they received (5ml/kg,i.p) normal saline daily, one hour after oral administration of distilled water. Tadalafil group received tadalafil (5mg/kg, P.O) for 12 days and on days 6-12, they received (5ml/kg,i.p) of normal saline daily, one hour after oral administration of tadalafil. Gentamicin group received distilled water (5ml/kg, P.O) and on days 6-12, they received gentamicin (100mg/kg,i.p) one hour after oral administration of distilled water. Gentamicin+Tadalafil group received tadalafil (5mg/kg, P.O) for 12 days and on days 6-12, they received gentamicin (100mg/kg,i.p) one hour after oral administration of tadalafil. Body weight and kidney weight were investigated. Urine volume as well as urinary albumin, creatinine, creatinine clearance and albumin /creatinine ratio (ACR) were evaluated. Besides, serum levels of urea and creatinine were measured as kidney function parameters. Renal tissues oxidative stress markers as malondialdehyde (MDA) and the antioxidant enzymes as superoxide dismutase (SOD) and catalase (CAT) activities. Renal cortex nitric oxide (NO) and kidney injury molecule-1 (KIM-1) were evaluated. Histological analysis and immunohistochemical expression of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) were performed. The results of the present study showed that GNT decreased creatinine clearance and increased the serum levels of renal function parameters. GNT caused a significant increase in renal cortex MDA, NO and urine levels of KIM-1, while it decreased CAT and SOD activities. Gentamicin administration resulted in increased immunohistochemical expression of iNOS enzyme while decreasing eNOS expression. Renal corpuscles and tubules also showed histological and ultrastructural changes. Pretreatment with tadalafil, on the other hand, reversed the effects of GNT administration. In conclusion, findings of the present study indicate that tadalafil reduces GNT-induced kidney damage by inhibition of inflammation, oxidative stress, and apoptosis.

Bacterial keratitis is the most common corneal infection which may lead to blindness, and seriously threatened the human visual health worldwide. Clinical treatment with antibiotic eye drops formulation usually falls in low bioavailability and poor therapeutic efficiency. Hydrogel has gained much attention as ophthalmic formulation recently due to the prolonged drug retention on ocular surface. In this study, we proposed a type of all-small-molecule supramolecular hydrogel assembled from guanosine-5′-monophosphate disodium salt and tobramycin for the treatment of bacterial keratitis. Guanosine-5′-monophosphate disodium salt assembled into guanosine-quartet nanofibers via hydrogen bonding and π-π stacking, and tobramycin with five primary amine groups further crosslinked the nanofibers bearing multiple phosphate moieties into gel networks via ionic interactions. The supramolecular gel showed shear thinning and thixotropic properties, good biocompatibility, and antibacterial activity. The gel treatment significantly ameliorated P. aeruginosa induced bacterial keratitis, and showed higher therapeutic efficacy compared to tobramycin eye drop. This study provides a facile and efficient antibiotic gel formulation for clinical treatment of bacterial keratitis.

Approximately 11% of genetic human diseases are caused by nonsense mutations that introduce a premature termination codon (PTC) into the coding sequence. The PTC results in the production of a potentially harmful shortened polypeptide and activation of a nonsense-mediated decay (NMD) pathway. The NMD pathway reduces the burden of unproductive protein synthesis by lowering the level of PTC mRNA. There is an endogenous rescue mechanism that produces a full-length protein from a PTC mRNA. Nonsense suppression therapies aim to increase readthrough, suppress NMD, or are a combination of both strategies. Therefore, treatment with translational readthrough-inducing drugs (TRIDs) and NMD inhibitors may increase the effectiveness of PTC suppression. Here we discuss the mechanism of PTC readthrough and the development of novel approaches to PTC suppression. We also discuss the toxicity and bioavailability of therapeutics used to stimulate PTC readthrough. [ABSTRACT FROM AUTHOR]

Plazomicin is a recent U.S. Food and Drug Administration (FDA)-approved semisynthetic aminoglycoside. Its structure consists of a sisomicin scaffold modified by adding a 2(S)-hydroxy aminobutyryl group at the N1 position and a hydroxyethyl substituent at the 6′ position. These substitutions produced a molecule refractory to most aminoglycoside-modifying enzymes. The main enzyme within this group that recognizes plazomicin as substrate is the aminoglycoside 2′-N-acetyltransferase type Ia [AAC(2′)-Ia], which reduces the antibiotic's potency. Designing formulations that combine an antimicrobial with an inhibitor of resistance is a recognized strategy to extend the useful life of existing antibiotics. We have recently found that several metal ions inhibit the enzymatic inactivation of numerous aminoglycosides mediated by the aminoglycoside 6′-N-acetyltransferase type Ib [AAC(6′)-Ib]. In particular, Ag+, which also enhances the effect of aminoglycosides by other mechanisms, is very effective in interfering with AAC(6′)-Ib-mediated resistance to amikacin. Here we report that silver acetate is a potent inhibitor of AAC(2′)-Ia-mediated acetylation of plazomicin in vitro, and it reduces resistance levels of Escherichia coli carrying aac(2′)-Ia. The resistance reversion assays produced equivalent results when the structural gene was expressed under the control of the natural or the blaTEM-1 promoters. The antibiotic effect of plazomicin in combination with silver was bactericidal, and the mix did not show significant toxicity to human embryonic kidney 293 (HEK293) cells. [ABSTRACT FROM AUTHOR]

This research focuses on combating the increasing problem of antimicrobial resistance, especially in Escherichia coli (E. coli), by assessing the efficacy of aminoglycosides. The study specifically addresses the challenge of developing new therapeutic approaches by integrating experimental data with mathematical modeling to better understand the action of aminoglycosides. It involves testing various antibiotics like streptomycin (SMN), kanamycin (KMN), gentamicin (GMN), tobramycin (TMN), and amikacin (AKN) against the O157:H7 strain of E. coli. The study employs a pharmacodynamics (PD) model to analyze how different antibiotic concentrations affect bacterial growth, utilizing minimum inhibitory concentration (MIC) to gauge the effective bactericidal levels of the antibiotics. The study’s approach involved transforming bacterial growth rates, as obtained from time–kill curve data, into logarithmic values. A model was then developed to correlate these log-transformed values with their respective responses. To generate additional data points, each value was systematically increased by an increment of 0.1. To simulate real-world variability and randomness in the data, a Gaussian scatter model, characterized by parameters like κ and EC50, was employed. The mathematical modeling was pivotal in uncovering the bactericidal properties of these antibiotics, indicating different PD MIC (zMIC) values for each (SMN: 1.22; KMN: 0.89; GMN: 0.21; TMN: 0.32; AKN: 0.13), which aligned with MIC values obtained through microdilution methods. This innovative blend of experimental and mathematical approaches in the study marks a significant advancement in formulating strategies to combat the growing threat of antimicrobial-resistant E. coli, offering a novel pathway to understand and tackle antimicrobial resistance more effectively.

Evidence suggests that otologic injury from ototopical aminoglycoside preparations is infrequent when used to treat ear infections with an intact tympanic membrane. Meanwhile, parenteral administration of aminoglycosides, is well known to be associated with a significant incidence of cochlear and vestibular damage. The discrepancy between topical and parenteral ototoxic effects is thought to result from a combination of factors, including the protective function of debris overlying the round window membrane, low antibiotic concentrations of topical antibiotic preparations, length of exposure and inability to detect subtle hearing or vestibular changes. Herein, we present a case of acute vestibulopathy following a 2-week course of topical gentamicin otic drops. Awareness of vestibulotoxicity following topical gentamicin therapy is prudent as vestibulopathic symptoms can be severely debilitating. [ABSTRACT FROM AUTHOR]

Background: Enterococci are main normal microbial flora of both humans and animals and can survive in a diverse range of environments. These bacteria carry out aminoglycoside and vancomycin resistance genes and spread them in environment by many routs such as chicken meat products. The present study was aimed to determine the frequency of aminoglycoside and vancomycin resistant genes in Enterococcus species isolated from chicken meat specimens. Methods: A total of 250 chicken raw meat specimens was prepared from slaughterhouses at Zanjan province, cultured at BHI broth and incubated at 37°C for 24h. The positive cultures were sub-cultured in blood agar plates and grown colonies identified using phenotypical and biochemical tests. Antibiotic susceptibility was determined according to the Clinical and Laboratory Standards Institute (CLSI) standards and PCR assays were performed to detect vanA, vanB, aph (2")1c, aph (2")1b, aph (2")1d, ant(3'), aph(3')IIIa, ant(4')1a, ant(6') and aac(6') genes. Results: In total, 100 Enterococcus species isolated from 250 specimens and 35% of them belonged to E. faecalis and the others were E. faecium (65%). The prevalence of the vanA, vanB, aph (2")1c, aph (2")1b, aph (2")1d, ant(3'), aph(3')IIIa, ant(4')1a, ant(6') and aac(6') genes among the 100 Enterococcus species was 14%, 12%, 10%, 1%, 2%, 50%, 26%, 9%, 18% and 22%, respectively. Conclusion: The current study revealed that the rate of antimicrobial resistance genes to aminoglycosides and vancomycin was worrying and health measurements in meat products industries must be performed to prevent spread of antimicrobial resistance elements among bacteria.

Background: Enterococci are main normal microbial flora of both humans and animals and can survive in a diverse range of environments. These bacteria carry out aminoglycoside and vancomycin resistance genes and spread them in environment by many routs such as chicken meat products. The present study was aimed to determine the frequency of aminoglycoside and vancomycin resistant genes in Enterococcus species isolated from chicken meat specimens. Methods: A total of 250 chicken raw meat specimens was prepared from slaughterhouses at Zanjan province, cultured at BHI broth and incubated at 37°C for 24h. The positive cultures were sub-cultured in blood agar plates and grown colonies identified using phenotypical and biochemical tests. Antibiotic susceptibility was determined according to the Clinical and Laboratory Standards Institute (CLSI) standards and PCR assays were performed to detect vanA, vanB, aph (2")1c, aph (2")1b, aph (2")1d, ant(3'), aph(3')IIIa, ant(4')1a, ant(6') and aac(6') genes. Results: In total, 100 Enterococcus species isolated from 250 specimens and 35% of them belonged to E. faecalis and the others were E. faecium (65%). The prevalence of the vanA, vanB, aph (2")1c, aph (2")1b, aph (2")1d, ant(3'), aph(3')IIIa, ant(4')1a, ant(6') and aac(6') genes among the 100 Enterococcus species was 14%, 12%, 10%, 1%, 2%, 50%, 26%, 9%, 18% and 22%, respectively. Conclusion: The current study revealed that the rate of antimicrobial resistance genes to aminoglycosides and vancomycin was worrying and health measurements in meat products industries must be performed to prevent spread of antimicrobial resistance elements among bacteria. [ABSTRACT FROM AUTHOR]

Background and Aim: Shigella is the causative agent of shigellosis in the world. Antibiotic treatment is important in this bacterium, but recently Shigella species containing the aph, aadE, aacA-aphD genes have shown resistance to aminoglycosides and have hampered the treatment process. Therefore, the aim of this study is a molecular investigation of Shigella dysenteriae aminoglycoside resistance genes isolated from children and its expression under the influence of curcumin nanoparticles. Materials and Methods: In this study, 60 diarrhea samples collected from Tehran hospitals in 2022 were used. Shigella dysenteriae isolates were identified by biochemical and microbial tests. The presence of aadE, aacA-aphD, and aph genes was confirmed by the Multiplex-PCR method. Then, real-time PCR was used to investigate the expression of aadE gene in the presence of curcumin nanoparticles. Results: From the 60 diarrhea samples examined, 12 strains (40%) of Shigella dysenteriae were identified by biochemical tests. Ten isolates (83.3%) carried the aadE gene, six isolates carried the aacA_aphD gene, and one isolate carried the aph gene. The Sub MIC value of curcumin nanoparticles on aadE gene expression is 128 µg/mL, and the Fold Change for this gene is -1.03. Conclusion: Considering the presence of aadE gene in 83.3% of S. dysenteriae isolates, it is important to investigate the presence of this gene in providing a suitable treatment model for patients infected with this bacterium, as well as the expression of aadE gene as the most common one. The expression of the aminoglycoside resistance gene was reduced to a relative amount in the presence of curcumin nanoparticles. Therefore, curcumin nanoparticles can be a suitable alternative for the treatment of strains carrying aminoglycoside resistance genes. [ABSTRACT FROM AUTHOR]

Introduction: Gentamicin is a conventional antibiotic in clinic. However, with the wide use of antibiotics, gentamicin-resistant Escherichia coli (E. coli) is an ever-increasing problem that causes infection in both humans and animals. Thus, it is especially important to restore gentamicin-mediated killing efficacy. Method: E. coli K12 BW25113 cells were passaged in medium with and without gentamicin and obtain gentamicin-resistant (K12-RGEN) and control (K12-S) strains, respectively. Then, the metabonomics of the two strains were analyzed by GC-MS approach. Results: K12-RGEN metabolome was characterized as more decreased metabolites than increased metabolites. Meantime, in the most enriched metabolic pathways, almost all of the metabolites were depressed. Alanine, aspartate and glutamate metabolism and glutamine within the metabolic pathway were identified as the most key metabolic pathways and the most crucial biomarkers, respectively. Exogenous glutamine potentiated gentamicin-mediated killing efficacy in glutamine and gentamicin dose-and time-dependent manners in K12-RGEN. Further experiments showed that glutamine-enabled killing by gentamicin was effective to clinically isolated multidrug-resistant E. coli. Discussion: These results suggest that glutamine provides an ideal metabolic environment to restore gentamicin-mediated killing, which not only indicates that glutamine is a broad-spectrum antibiotic synergist, but also expands the range of metabolites that contribute to the bactericidal efficiency of aminoglycosides. [ABSTRACT FROM AUTHOR]

Background: The treatment of swine dysentery (SD) has become constrained in recent years due to the limited availability of effective drugs combined with a rise in antimicrobial resistance. Gentamicin, an aminoglycoside antibiotic, is authorised for the control of this disease in several European countries but has not been extensively used so far. In this study, the in vitro susceptibility of 56 Brachyspira hyodysenteriae field isolates was evaluated against gentamicin using a broth microdilution test. The molecular basis of decreased susceptibility to gentamicin was also investigated by sequencing the 16S rRNA gene and phylogenetic relatedness by multiple-locus variable number tandem-repeat analysis (MLVA). Results: Most B. hyodysenteriae isolates presented low minimum inhibitory concentration (MIC) values to gentamicin, with a mode of 2 µg/mL, a median or MIC50 of 4 µg/mL and percentile 90 or MIC90 of 16 µg/mL. The distribution of these values over the period studied (2011–2019) did not show a tendency towards the development of resistance to gentamicin. Differences in susceptibility among isolates could be explained by two point-mutations in the 16S rRNA gene, C990T and A1185G, which were only present in isolates with high MICs. These isolates were typed in three different MLVA clusters. Analyses of co-resistance between gentamicin and antimicrobials commonly used for the treatment of SD revealed that resistance to tiamulin and valnemulin was associated with low MICs for gentamicin. Conclusions: The results provide an accurate characterisation of antimicrobial sensitivity to gentamicin and possible mechanisms of resistance in Spanish B. hyodysenteriae isolates. These findings allow us to propose gentamicin as an alternative in the antibiotic management of SD, particularly in outbreaks caused by pleuromutilin resistant isolates. [ABSTRACT FROM AUTHOR]

OBJECTIVE Aminoglycosides are frequently used for empiric and definitive treatment of cystic fibrosis (CF) pulmonary exacerbations. Various methods have been described for aminoglycoside therapeutic drug monitoring. The objective of this study is to evaluate the effect of patient-specific pharmacokinetic calculations for aminoglycosides used to treat CF pulmonary exacerbations. METHODS Ambidirectional cohort study of patients admitted to a children's hospital from June 1, 2018, through February 28, 2019, and June 1, 2019, through February 8, 2021. The primary outcome was the occurrence of dosing changes after analysis of initial serum concentrations in either group. Secondary outcomes included occurrence of nephrotoxicity, duration of antibiotics, and length of stay. RESULTS Twenty-four patients (75%) in the intervention group versus zero in the control group required dosing adjustments after initial analysis of serum concentrations were completed (p < 0.001). There was not a statistically significant between-group difference for duration of antibiotics in days (median, 14 vs 13.5; Z, 1.07; p = 0.29) or length of stay (median, 11 vs 11; Z, -0.31; p = 0.76). There was also not a statistically significant between-group difference in forced expiratory volume in one second (FEV1) change from admission to discharge (11.4% vs 13.9%; t, 0.61; Degrees of Freedom, 39; p = 0.55). Two patients (6.25%) in the intervention group experienced nephrotoxicity compared with zero patients in the control group (risk difference, 6.25%; 95% CI, -2.14 to 14.64; number needed to harm, 16). CONCLUSIONS Patient-specific pharmacokinetic monitoring led to significantly more dosing changes and was associated with similar patient outcomes as trough-only monitoring. Further studies are needed to identify methods to optimize aminoglycoside dosing and monitoring for these patients with the goal of reducing toxicities while maximizing efficacy. ABBREVIATIONS AUC, area under the curve; CF, cystic fibrosis; Cmax, maximum serum concentration; Cmin, minimum serum concentration; DFI, drug-free interval; FEV1, forced expiratory volume in one second; IV, intravenous; MIC, minimum inhibitory concentration; PK, pharmacokinetic. [ABSTRACT FROM AUTHOR]

Chemical modification of old drugs is an important way to obtain new ones, and it has been widely used in developing new aminoglycoside antibiotics. However, many of the previous modifying strategies seem arbitrary for their lack of support from structural biological detail. In this paper, based on the structural information of aminoglycoside and its drug target, we firstly analyzed the reason that some 2′-N-acetylated products of aminoglycosides caused by aminoglycoside-modifying enzyme AAC(2′) can partially retain activity, and then we designed, synthesized, and evaluated a series of 2′-modified kanamycin A derivatives. Bioassay results showed our modifying strategy was feasible. Our study provided valuable structure–activity relationship information, which would help researchers to develop new aminoglycoside antibiotics more effectively. [ABSTRACT FROM AUTHOR]

Background and purpose: Aminoglycosides (AG) such as Amikacin that are widely used to prevent and treat infections in neonates have nephrotoxic effects. The aim of this study was to evaluate the role of urinary index to Glomerular filtration rate (GFR) in diagnosis of tubular renal injury following administration of Amikacin in neonates admitted to neonatal intensive care unit (NICU). Materials and methods: In this descriptive cross-sectional study, 45 neonates admitted to NICU with confirmed sepsis undergone treatment with Amikacin and Ampicillin and 45 neonates were treated with Ampicillin and Cefotaxime. GFR was calculated using Schwartz's formula (serum creatinine/height * 0.45) and categorized based on Fanaroff table. In both groups, BUN, Cr, and GFR were measured at days one and seven. Data analysis was performed in SPSS. Results: Two (4.4%) patients in the group treated with Amikacin and Ampicillin and one (2.2%) in the group who received Ampicillin and Cefotaxime developed acute kidney injury (AKI). GFR changes and Cr levels at day seven were not found to be significantly different between septic neonates treated with Amikacin and Ampicillin and neonates treated with other non-aminoglycosidic antibiotics (P>0.05). Conclusion: There was no difference in incidence of AKI between neonates receiving Amikacin and Ampicillin and those who received Ampicillin and Cefotaxime. Hence, AKI in these neonates requires further evaluations.

Objective(s): In this study, it is aimed to investigate the potential protective effect of caffeic acid phenethyl ester (CAPE) on ototoxicity caused by gentamicin in a rat model.Materials and Methods: Thirty Wistar albino rats were divided into 3 groups. Group I was selected as the control group. Gentamicin was administered intraperitoneally in group II, gentamicin and CAPE in group III. Audiological assessment was performed by the distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) measurements before and after treatment of each group. At the end of the study all rats were decapitated, cochlea was removed and electron microscopic examination was performed. Results: In group II post-treatment DPOAE levels were found to be lower than pretreatment DPOAE levels (P0.05). Except for Group I, ABR thresholds increased after the procedure and this increase was statistically significant (P

Sensory hair cell death caused by the ototoxic side effects of many clinically used drugs leads to permanent sensorineural hearing loss in patients. Aminoglycoside antibiotics are widely used and well-known for their ototoxicity, but the molecular mechanisms of aminoglycoside-induced hair cell death are not well understood. This creates challenges in our attempts to alleviate or prevent such adverse side effects. Here, we report a regulatory role of CDK2 in aminoglycoside-induced hair cell death. Utilizing organotypic cultures of cochleae from neonatal mice, we show that blocking CDK2 activity by either pharmaceutical inhibition or by Cdk2 gene knockout protects hair cells against the ototoxicity of gentamicin--one of the most commonly used aminoglycoside antibiotics--by interfering with intrinsic programmed cell death processes. Specifically, we show that CDK2 inhibition delays the collapse of mitochondria and the activation of a caspase cascade. Furthermore, at the molecular level, inhibition of CDK2 activity influences proapoptotic JNK signaling by reducing the protein level of c-Jun and suppressing the gentamicin-induced upregulation of c-Jun target genes Jun and Bim. Our in vivo studies reveal that Cdk2 gene knockout animals are significantly less sensitive to gentamicin ototoxicity compared to wild-type littermates. Altogether, our work ascertains the non-cell cycle role of CDK2 in regulating aminoglycoside-induced hair cell apoptosis and sheds lights on new potential strategies for hearing protection against ototoxicity. [ABSTRACT FROM AUTHOR]

Background: Gentamicin (GNT) is a highly effective aminoglycoside antibiotic that is commonly used to treat life-threatening bacterial infections. Aim: The aim of the current study is to determine whether tadalafil can protect against GNT-induced nephrotoxicity. Methods: Twenty-four male Albino rats were used in the study, which were randomly divided into four groups, six animals each. Control untreated group received distilled water (5ml/kg, P.O) for 12 days and on days 6-12, they received (5ml/kg,i.p) normal saline daily, one hour after oral administration of distilled water. Tadalafil group received tadalafil (5mg/kg, P.O) for 12 days and on days 6-12, they received (5ml/kg,i.p) of normal saline daily, one hour after oral administration of tadalafil. Gentamicin group received distilled water (5ml/kg, P.O) and on days 6-12, they received gentamicin (011mg/kg,i.p) one hour after oral administration of distilled water. Gentamicin+Tadalafil group received tadalafil (5mg/kg, P.O) for 12 days and on days 6-12, they received gentamicin (100mg/kg,i.p) one hour after oral administration of tadalafil. Body weight and kidney weight were investigated. Urine volume as well as urinary albumin, creatinine, creatinine clearance and albumin/creatinine ratio (ACR) were evaluated. Besides, serum levels of urea and creatinine were measured as kidney function parameters. Renal tissues oxidative stress markers as malondialdehyde (MDA) and the antioxidant enzymes as superoxide dismutase (SOD) and catalase (CAT) activities. Renal cortex nitric oxide (NO) and kidney injury molecule-1 (KIM-1) were evaluated. Histological analysis and immunohistochemical expression of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) were performed. The results of the present study showed that GNT decreased creatinine clearance and increased the serum levels of renal function parameters. GNT caused a significant increase in renal cortex MDA, NO and urine levels of KIM-1, while it decreased CAT and SOD activities. Gentamicin administration resulted in increased immunohistochemical expression of iNOS enzyme while decreasing eNOS expression. Renal corpuscles and tubules also showed histological and ultrastructural changes. Pretreatment with tadalafil, on the other hand, reversed the effects of GNT administration. In conclusion, findings of the present study indicate that tadalafil reduces GNT-induced kidney damage by inhibition of inflammation, oxidative stress, and apoptosis. [ABSTRACT FROM AUTHOR]

Background and Aim: Vancomycin resistant Enterococci (VRE) and high level aminoglycoside resistant (HLAR) Enterococci have complicated the available treatment modalities for Enterococci worldwide. The existing study was planned to evaluate the occurrence of HLAR and VRE strains in a tertiary care center in India and to study the association of HLAR with vancomycin sensitive Enterococci (VSE) and VRE. Materials and Methods: A total of 50 enterococcal isolates from various clinical specimens were incorporated in the study. Speciation was done on the basis of standard biochemical tests. HLAR was tested by the disc diffusion method using 150μg gentamicin disc and 200 μg streptomycin discs. Vancomycin susceptibility patterns were reported using vancomycin disc and agar dilution methods. Results & Conclusion: Pus samples comprised of the majority for the isolation of enterococcal strains (40%). 54% isolated strains were HLGR, 32% were HLSR and 14% isolates were positive for both HLGR and HLSR. 61.7% of Enterococcus faecium isolates demonstrated resistance for high-level gentamicin (HLGR) and 43.75% Enterococcus faecalis isolates were resistant to high-level streptomycin (HLSR). When VRE was compared to VSE, the rate of HLSR was detected to be 4.64% in VRE, while it was 32.55% in VSE; the rate of HLGR was noted to be 11.62% in VRE and it was 41.87% in VSE. The association of HLGR with HLSR (HLAR) was 2.32% in VRE and 13.95% in VSE strains. Enterococci strains are showing an increase in their antimicrobial resistance patterns. The increment of such strains in health care settings has to be reserved and controlled to avert complicated infections. [ABSTRACT FROM AUTHOR]

Antibiotic resistance of bacterial pathogens has become a severe threat to human health. To counteract antibiotic resistance, it is of significance to discover new antibiotics and also improve the efficacy of existing antibiotics. Here we show that 5-methylindole, a derivative of the interspecies signaling molecule indole, is able to directly kill various Gram-positive pathogens (e.g., Staphylococcus aureus and Enterococcus faecalis) and also Gram-negative ones (e.g., Escherichia coli and Pseudomonas aeruginosa), with 2-methylindole being less potent. Particularly, 5-methylindole can kill methicillin-resistant S. aureus, multidrug-resistant Klebsiella pneumoniae, Mycobacterium tuberculosis, and antibiotic-tolerant S. aureus persisters. Furthermore, 5-methylindole significantly potentiates aminoglycoside antibiotics, but not fluoroquinolones, killing of S. aureus. In addition, 5-iodoindole also potentiates aminoglycosides. Our findings open a new avenue to develop indole derivatives like 5-methylindole as antibacterial agents or adjuvants of aminoglycoside. [ABSTRACT FROM AUTHOR]

The ongoing arms race between bacteria and phages has forced bacteria to evolve a sophisticated set of antiphage defense mechanisms that constitute the bacterial immune system. In our previous study, we highlighted the antiphage properties of aminoglycoside antibiotics, which are naturally secreted by Streptomyces . Successful inhibition of phage infection was achieved by addition of pure compounds and supernatants from a natural producer strain emphasizing the potential for community-wide antiphage defense. However, given the dual functionality of these compounds, neighboring bacterial cells require resistance to the antibacterial activity of aminoglycosides to benefit from the protection they confer against phages. In this study, we tested a variety of different aminoglycoside resistance mechanisms acting via drug or target (16S rRNA) modification and demonstrated that they do not interfere with the antiphage properties of the molecules. Furthermore, we confirmed the antiphage impact of aminoglycosides in a community context by coculturing phage-susceptible, apramycin-resistant Streptomyces venezuelae with the apramycin-producing strain Streptoalloteichus tenebrarius . Given the prevalence of aminoglycoside resistance among natural bacterial isolates, this study highlights the ecological relevance of chemical defense via aminoglycosides at the community level., Competing Interests: The authors declare no conflict of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Aminoglycoside antibiotics target ribosomes and are effective against a wide range of bacteria. Here, we demonstrated that knockout strains related to energy metabolism in Escherichia coli showed increased tolerance to aminoglycosides during the mid-exponential growth phase. Contrary to expectations, these mutations did not reduce the proton motive force or aminoglycoside uptake, as there were no significant changes in metabolic indicators or intracellular gentamicin levels between wild-type and mutant strains. Our comprehensive proteomics analysis unveiled a noteworthy upregulation of proteins linked to the tricarboxylic acid (TCA) cycle in the mutant strains during the mid-exponential growth phase, suggesting that these strains compensate for the perturbation in their energy metabolism by increasing TCA cycle activity to maintain their membrane potential and ATP levels. Furthermore, our pathway enrichment analysis shed light on local network clusters displaying downregulation across all mutant strains, which were associated with both large and small ribosomal binding proteins, ribosome biogenesis, translation factor activity, and the biosynthesis of ribonucleoside monophosphates. These findings offer a plausible explanation for the observed tolerance of aminoglycosides in the mutant strains. Altogether, this research provides valuable insights into the mechanisms of aminoglycoside tolerance, paving the way for novel strategies to combat such cells., Competing Interests: RS, MO No competing interests declared, (© 2024, Shiraliyev and Orman.)