Low-dose amikacin in the treatment of Multidrug-resistant Tuberculosis (MDR-TB)

Apramycin has high in vitro activity against Mycobacterium tuberculosis

Introduction. Aminoglycoside antibiotics such as amikacin and kanamycin are important components in the treatment of Mycobacterium tuberculosis (Mtb) infection. However, more and more clinical strains are found to be aminoglycoside antibiotic-resistant. Apramycin is another kind of aminoglycoside antibiotic that is commonly used to treat infections in animals.Hypothesis. Apramycin may have in vitro activity against Mtb.Aim. This study aims to evaluate the efficacy of apramycin against Mtb in vitro and determine its epidemiological cut-off (ECOFF) value.Methodology. One hundred Mtb isolates, including 17 pansusceptible and 83 drug-resistant tuberculosis (DR-TB) strains, were analysed for apramycin resistance using the MIC assay.Results. Apramycin exhibited significant inhibitory activity against Mtb clinical isolates, with an MIC50 of 0.5 μg ml-1 and an MIC90 of 1 μg ml-1. We determined the tentative ECOFF value as 1 µg ml-1 for apramycin. The resistant rates of multidrug-resistant tuberculosis (MDR-TB), pre-extensively drug-resistant (pre-XDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) strains were 12.12 % (4/33), 20.69 % (6/29) and 66.67 % (14/21), respectively. The rrs gene A1401G is associated with apramycin resistance, as well as the cross-resistance between apramycin and other aminoglycosides.Conclusion. Apramycin shows high in vitro activity against the Mtb clinical isolates, especially the MDR-TB clinical isolates. This encouraging discovery calls for more research on the functions of apramycin in vivo and as a possible antibiotic for the treatment of drug-resistant TB.

Drug recommendation for optimization on treatment outcome for MDR/RR-TB based on a multi-center, large scale, retrospective cohort study in China

OBJECTIVE

With the change in drug-resistant pattern, MDR/RR-TB was faced with underlying changes in regimens. A multi-center, large-scale, retrospective study performed aims to provide a recommendation of drug selection on optimization of outcome for the patients.

METHOD

The study was conducted in six TB-specialized hospitals in China. Patients were included from 2018-2021 and followed up throughout the treatment. Using a multivarariable and propensity score-matched logistic regression analysis, we evaluated associations between outcomes and drug use, as well as clinical characteritics.

RESULTS

Of 3112 patients, 74.29% had treatment sucess, 14.52% lost to follow-up, 9.67% failure, and 1.51% died. Treatment success was positively associated with Bedaquiline(Bdq), Linezolid(Lzd), and Cycloserin(Cs). Capreomycin(Cm) increased the risk of unfavorable outcomes. other drugs such as Amikacin(Amk) and clofazimine had no significant effect on outcomes. If isolates were susceptible to fluoroquinolones(FQs), FQs could decrease the risk of unfavorable outcomes.

CONCLUSIONS

The recommendation order for the treatment of MDR/RR-TB is Bdq, Lzd, and Cs. FQs were decreased in use intensity. Injection drugs, whether Amk or Cm, are not recommended.

Comparative Proteomic Analysis of Capsule Proteins in Aminoglycoside-Resistant and Sensitive Mycobacterium tuberculosis Clinical Isolates: Unraveling Potential Drug Targets

BACKGROUND

Tuberculosis (TB), a global infectious threat, has seen a concerning rise in aminoglycoside-resistant Mycobacterium tuberculosis (M.tb) strains. The potential role of capsule proteins remains largely unexplored. This layer acts as the primary barrier for tubercle bacilli, attempting to infiltrate host cells and subsequent disease development.

METHODS

The study aims to bridge this gap by investigating the differentially expressed capsule proteins in aminoglycoside-resistant M.tb clinical isolates compared with drug-sensitive isolates employing two-dimensional gel electrophoresis, mass spectrometry, and bioinformatic approaches.

RESULTS

We identified eight proteins that exhibited significant upregulation in aminoglycoside-resistant isolates. Protein Rv3029c and Rv2110c were associated with intermediary metabolism and respiration; Rv2462c with cell wall and cell processes; Rv3804c with lipid metabolism; Rv2416c and Rv2623 with virulence and detoxification/adaptation; Rv0020c with regulatory functions; and Rv0639 with information pathways. Notably, the Group-based Prediction System for Prokaryotic Ubiquitin-like Protein (GPS-PUP) algorithm identified potential pupylation sites within all proteins except Rv3804c. Interactome analysis using the STRING 12.0 database revealed potential interactive partners for these proteins, suggesting their involvement in aminoglycoside resistance. Molecular docking studies revealed suitable binding between amikacin and kanamycin drugs with Rv2462c, Rv3804c, and Rv2623 proteins.

CONCLUSION

As a result, our findings illustrate the multifaceted nature of aminoglycoside resistance in M.tb and the importance of understanding how capsule proteins play a role in counteracting drug efficacy. Identifying the role of these proteins in drug resistance is crucial for developing more effective treatments and diagnostics for TB.

Restoring susceptibility to aminoglycosides: identifying small molecule inhibitors of enzymatic inactivation

Growing resistance to antimicrobial medicines is a critical health problem that must be urgently addressed. Adding to the increasing number of patients that succumb to infections, there are other consequences to the rise in resistance like the compromise of several medical procedures and dental work that are heavily dependent on infection prevention. Since their introduction in the clinics, aminoglycoside antibiotics have been a critical component of the armamentarium to treat infections. Still, the increase in resistance and their side effects led to a decline in their utilization. However, numerous current factors, like the urgent need for antimicrobials and their favorable properties, led to renewed interest in these drugs. While efforts to design new classes of aminoglycosides refractory to resistance mechanisms and with fewer toxic effects are starting to yield new promising molecules, extending the useful life of those already in use is essential. For this, numerous research projects are underway to counter resistance from different angles, like inhibition of expression or activity of resistance components. This review focuses on selected examples of one aspect of this quest, the design or identification of small molecule inhibitors of resistance caused by enzymatic modification of the aminoglycoside. These compounds could be developed as aminoglycoside adjuvants to overcome resistant infections.

Whole-genome sequencing and transcriptome-characterized in vitro evolution of aminoglycoside resistance in Mycobacterium tuberculosis

Antibiotic resistance of Mycobacterium tuberculosis (Mtb) is a major public health concern worldwide. Therefore, it is of great significance to characterize the mutational pathways by which susceptible Mtb evolves into drug resistance. In this study, we used laboratory evolution to explore the mutational pathways of aminoglycoside resistance. The level of resistance in amikacin inducing Mtb was also associated with changes in susceptibility to other anti-tuberculosis drugs such as isoniazid, levofloxacin and capreomycin. Whole-genome sequencing (WGS) revealed that the induced resistant Mtb strains had accumulated diverse mutations. We found that rrs A1401G was the predominant mutation in aminoglycoside-resistant clinical Mtb isolates from Guangdong. In addition, this study provided global insight into the characteristics of the transcriptome in four representative induced strains and revealed that rrs mutated and unmutated aminoglycoside-resistant Mtb strains have different transcriptional profiles. WGS analysis and transcriptional profiling of Mtb strains during evolution revealed that Mtb strains harbouring rrs A1401G have an evolutionary advantage over other drug-resistant strains under the pressure of aminoglycosides because of their ultra-high resistance level and low physiological impact on the strain. The results of this study should advance our understanding of aminoglycoside resistance mechanisms.

Prevalence of long-term physical sequelae among patients treated with multi-drug and extensively drug-resistant tuberculosis: a systematic review and meta-analysis

BACKGROUND

Physical sequelae related to multi-drug resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) are emerging and under-recognised global challenges. This systematic review and meta-analysis aimed to quantify the prevalence and the types of long-term physical sequelae associated with patients treated for MDR- and XDR-TB.

METHODS

We systematically searched CINAHL (EBSCO), MEDLINE (via Ovid), Embase, Scopus, and Web of Science from inception through to July 1, 2022, and the last search was updated to January 23, 2023. We included studies reporting physical sequelae associated with all forms of drug-resistant TB, including rifampicin-resistant TB (RR-TB), MDR-TB, Pre-XDR-TB, and XDR-TB. The primary outcome of interest was long-term physical sequelae. Meta-analysis was conducted using a random-effect model to estimate the pooled proportion of physical sequelae. The sources of heterogeneity were explored through meta-regression using study characteristics as covariates. The research protocol was registered in PROSPERO (CRD42021250909).

FINDINGS

From 3047 unique publications identified, 66 studies consisting of 37,380 patients conducted in 30 different countries were included in the meta-analysis. The overall pooled estimate was 44.4% (95% Confidence Interval (CI): 36.7-52.1) for respiratory sequelae, 26.7% (95% CI: 23.85-29.7) for hearing sequelae, 10.1% (95% CI: 7.0-13.2) for musculoskeletal sequelae, 8.4% (95% CI: 6.5-10.3) for neurological sequelae, 8.1% (95% CI: 6.3-10.0) for renal sequelae, 7.3% (95% CI: 5.1-9.4) for hepatic sequelae, and 4.5% (95% CI: 2.7-6.3) for visual sequelae. There was substantial heterogeneity in the estimates. The stratified analysis showed that the pooled prevalence of hearing sequelae was 26.6% (95% CI: 12.3-40.9), neurological sequelae was 31.5% (95% CI: 5.5-57.5), and musculoskeletal sequelae were 21.5% (95% CI: 9.9-33.1) for patients with XDR-TB, which were higher than the pooled prevalence of sequelae among patients with MDR-TB. Respiratory sequelae were the highest in low-income countries (59.3%) and after completion of MDR-TB treatment (57.7%).

INTERPRETATION

This systematic review found that long-term physical sequelae such as respiratory, hearing, musculoskeletal, neurological, renal, hepatic, and visual sequelae were common among survivors of MDR- and XDR-TB. There was a significant difference in the prevalence of sequelae between patients with MDR- and XDR-TB. Post-MDR- and XDR-TB treatment surveillance for adverse outcomes needs to be incorporated into the current programmatic management of MDR-TB to enable early detection and prevention of post-treatment sequelae.

FUNDING

Australian National Health and Medical Research Council, through an Emerging Leadership Investigator grant, and the Curtin University Higher Degree Research scholarship.

Personalised Medicine for Tuberculosis and Non-Tuberculous Mycobacterial Pulmonary Disease

Personalised medicine, in which clinical management is individualised to the genotypic and phenotypic data of patients, offers a promising means by which to enhance outcomes in the management of mycobacterial pulmonary infections. In this review, we provide an overview of how personalised medicine approaches may be utilised to identify patients at risk of developing tuberculosis (TB) or non-tuberculous mycobacterial pulmonary disease (NTM-PD), diagnose these conditions and guide effective treatment strategies. Despite recent technological and therapeutic advances, TB and NTM-PD remain challenging conditions to diagnose and treat. Studies have identified a range of genetic and immune factors that predispose patients to pulmonary mycobacterial infections. Molecular tests such as nucleic acid amplification assays and next generation sequencing provide a rapid means by which to identify mycobacterial isolates and their antibiotic resistance profiles, thus guiding selection of appropriate antimicrobials. Host-directed therapies and therapeutic drug monitoring offer ways of tailoring management to the clinical needs of patients at an individualised level. Biomarkers may hold promise in differentiating between latent and active TB, as well as in predicting mycobacterial disease progression and response to treatment.

Development of Tinnitus and Hyperacusis in a Mouse Model of Tobramycin Cochleotoxicity

Aminoglycosides (AG) antibiotics are a common treatment for recurrent infections in cystic fibrosis (CF) patients. AGs are highly ototoxic, resulting in a range of auditory dysfunctions. It was recently shown that the acoustic startle reflex (ASR) can assess behavioral evidence of hyperacusis and tinnitus in an amikacin cochleotoxicity mouse model. The goal of this study was to establish if tobramycin treatment led to similar changes in ASR behavior and to establish whether ebselen can prevent the development of these maladaptive neuroplastic symptoms. CBA/Ca mice were divided into three groups: Group 1 served as a control and did not receive tobramycin or ebselen, Group 2 received tobramycin (200 mg/kg/s.c.) and the vehicle (DMSO/saline/i.p.) daily for 14 continuous days, and Group 3 received the same dose/schedule of tobramycin as Group 2 and ebselen at (20 mg/kg/i.p.). Auditory brainstem response (ABR) and ASR hearing assessments were collected at baseline and 2, 6, 10, 14, and 18 weeks from the start of treatment. ASR tests included input/output (I/O) functions which assess general hearing and hyperacusis, and Gap-induced prepulse inhibition of the acoustic startle (GPIAS) to assess tinnitus. At 18 weeks, histologic analysis showed predominantly normal appearing hair cells and spiral ganglion neuron (SGN) synapses. Following 14 days of tobramycin injections, 16 kHz thresholds increased from baseline and fluctuated over the 18-week recovery period. I/O functions revealed exaggerated startle response magnitudes in 50% of mice over the same period. Gap detection deficits, representing behavioral evidence of tinnitus, were observed in a smaller subset (36%) of animals. Interestingly, increases in ABR wave III/wave I amplitude ratios were observed. These tobramycin data corroborate previous findings that AGs can result in hearing dysfunctions. We show that a 14-day course of tobramycin treatment can cause similar levels of hearing loss and tinnitus, when compared to a 14-day course of amikacin, but less hyperacusis. Evidence suggests that tinnitus and hyperacusis might be common side effects of AG antibiotics.