Aminoglycoside induced ototoxicity associated with mitochondrial DNA mutations

Implementing next-generation sequencing for diagnosis and management of hereditary hearing impairment: a comprehensive review

INTRODUCTION

Sensorineural hearing impairment (SNHI), a common childhood disorder with heterogeneous genetic causes, can lead to delayed language development and psychosocial problems. Next-generation sequencing (NGS) offers high-throughput screening and high-sensitivity detection of genetic etiologies of SNHI, enabling clinicians to make informed medical decisions, provide tailored treatments, and improve prognostic outcomes.

AREAS COVERED

This review covers the diverse etiologies of HHI and the utility of different NGS modalities (targeted sequencing and whole exome/genome sequencing), and includes HHI-related studies on newborn screening, genetic counseling, prognostic prediction, and personalized treatment. Challenges such as the trade-off between cost and diagnostic yield, detection of structural variants, and exploration of the non-coding genome are also highlighted.

EXPERT OPINION

In the current landscape of NGS-based diagnostics for HHI, there are both challenges (e.g. detection of structural variants and non-coding genome variants) and opportunities (e.g. the emergence of medical artificial intelligence tools). The authors advocate the use of technological advances such as long-read sequencing for structural variant detection, multi-omics analysis for non-coding variant exploration, and medical artificial intelligence for pathogenicity assessment and outcome prediction. By integrating these innovations into clinical practice, precision medicine in the diagnosis and management of HHI can be further improved.

Aminoglycoside uptake, stress, and potentiation in Gram-negative bacteria: new therapies with old molecules

SUMMARYAminoglycosides (AGs) are long-known molecules successfully used against Gram-negative pathogens. While their use declined with the discovery of new antibiotics, they are now classified as critically important molecules because of their effectiveness against multidrug-resistant bacteria. While they can efficiently cross the Gram-negative envelope, the mechanism of AG entry is still incompletely understood, although this comprehension is essential for the development of new therapies in the face of the alarming increase in antibiotic resistance. Increasing antibiotic uptake in bacteria is one strategy to enhance effective treatments. This review aims, first, to consolidate old and recent knowledge about AG uptake; second, to explore the connection between AG-dependent bacterial stress and drug uptake; and finally, to present new strategies of potentiation of AG uptake for more efficient antibiotic therapies. In particular, we emphasize on the connection between sugar transport and AG potentiation.

Chronic neurotransmission increases the susceptibility of lateral-line hair cells to ototoxic insults

Sensory hair cells receive near constant stimulation by omnipresent auditory and vestibular stimuli. To detect and encode these stimuli, hair cells require steady ATP production, which can be accompanied by a buildup of mitochondrial byproducts called reactive oxygen species (ROS). ROS buildup is thought to sensitize hair cells to ototoxic insults, including the antibiotic neomycin. Work in neurons has shown that neurotransmission is a major driver of ATP production and ROS buildup. Therefore, we tested whether neurotransmission is a significant contributor to ROS buildup in hair cells. Using genetics and pharmacology, we disrupted two key aspects of neurotransmission in zebrafish hair cells: presynaptic calcium influx and the fusion of synaptic vesicles. We find that chronic block of neurotransmission enhances hair-cell survival when challenged with the ototoxin neomycin. This reduction in ototoxin susceptibility is accompanied by reduced mitochondrial activity, likely due to a reduced ATP demand. In addition, we show that mitochondrial oxidation and ROS buildup are reduced when neurotransmission is blocked. Mechanistically, we find that it is the synaptic vesicle cycle rather than presynaptic- or mitochondrial-calcium influx that contributes most significantly to this metabolic stress. Our results comprehensively indicate that, over time, neurotransmission causes ROS buildup that increases the susceptibility of hair cells to ototoxins.

Impact of Therapeutic Drug Monitoring on Once-Daily Regimen of Amikacin in Patients With Urinary Tract Infection: A Prospective Observational Study

BACKGROUND

Amikacin is a semisynthetic antibiotic used in the treatment of gram-negative bacterial infections and has a narrow therapeutic index. Although therapeutic drug monitoring is recommended for amikacin, it is not routinely performed because of the use of a less toxic once-daily regimen. Only few studies have evaluated the role of therapeutic drug monitoring in patients treated with amikacin. The objective of our study was to find an association between the pharmacokinetic parameters of amikacin and the time required for a clinical cure, creatinine clearance, and frequency of ototoxicity in patients with urinary tract infection treated for 7 or more days.

METHODS

A prospective study was conducted on patients with urinary tract infections who were administered amikacin for 7 or more days. Blood samples were obtained from the patients to measure the maximum drug concentration (Cmax) and trough concentration (Ctrough). Minimum inhibitory concentration (MIC) values were determined for patients with positive urine cultures. Serum creatinine levels were estimated every 3 days. The auditory assessment was performed using pure tone audiometry at baseline and weekly until the patients were discharged. Levels of amikacin were analyzed using a validated liquid chromatography-tandem mass spectrometry method.

RESULTS

Of 125 patients analyzed, the median time required for a clinical cure was less in the group of patients who achieved a Cmax/MIC ratio ≥8 than it was in those who did not achieve this level [7 versus 8 days (P = 0.02)]. The Ctrough of amikacin was associated with the change in serum creatinine level (P = 0.01) and the incidence of nephrotoxicity (P = 0.004).

CONCLUSIONS

In patients receiving short-term amikacin therapy, Cmax/MIC value can be used to predict the time required for a clinical cure. Ctrough can be used to predict the occurrence of nephrotoxicity in patients receiving amikacin therapy.