In Vitro Bedaquiline and Clofazimine Susceptibility Testing in Mycobacterium abscessus

Bedaquiline susceptibility testing of Mycobacterium abscessus complex and Mycobacterium avium complex: A meta-analysis study

OBJECTIVE

This study aims to estimate the overall in vitro activity of bedaquiline (BDQ) against clinical isolates of Mycobacterium abscessus complex (MABS) and M. avium complex (MAC), considering BDQ as a repurposed drug for non-tuberculous mycobacteria (NTM) infections.

METHODS

We conducted a systematic review of publications in PubMed/ MEDLINE, Web of Science, and Embase up to 15 April 2023. Studies were included if they followed the Clinical and Laboratory Standards Institute (CLSI) criteria for drug susceptibility testing (DST). Using a random effects model, we assessed the overall in vitro BDQ resistance rate in clinical isolates of MABS and MAC. Sources of heterogeneity were analysed using Cochran's Q and the I2 statistic. All analyses were performed using CMA V3.0.

RESULTS

A total of 24 publications (19 reports for MABS and 11 for MAC) were included. Using 1 µg/mL and 2 µg/mL as the breakpoint for BDQ resistance, the pooled rates of in vitro BDQ resistance in clinical isolates of MABS were found to be 1.8% (95% confidence interval [CI], 0.7-4.6%) and 1.7% (95% CI, 0.6-4.4%), respectively. In the case of MAC, the pooled rates were 1.7% (95% CI, 0.4-6.9%) and 1.6% (95% CI, 0.4-6.8%) for 1 µg/mL and 2 µg/mL, respectively.

CONCLUSION

This study reports the prevalence of BDQ resistance in clinical isolates of MABS and MAC. The findings suggest that BDQ holds potential as a repurposed drug for treating MABS and MAC infections.

Antimicrobial susceptibility of Mycobacterium abscessus and treatment of pulmonary and extra-pulmonary infections

BACKGROUND

Mycobacterium abscessus (MAB) is the mycobacterial species least susceptible to antimicrobials. Infections are difficult to treat, and cure rates are below 50% even after a combination of 4-5 drugs for many months.

OBJECTIVES

To examine antimicrobial susceptibilities and treatment recommendations in light of what is known about mechanisms of resistance and pharmacodynamics/pharmacokinetics (PK/PD) interactions.

SOURCES

Original papers on the topics of 'antimicrobials', 'susceptibility', 'treatment', and 'outcome' from 2019 onwards, in the context of the evidence brought by the guidelines published in 2020 for pulmonary infections.

CONTENT

MAB is susceptible in vitro to only a few antimicrobials. Breakpoints were set by the Clinical and Laboratory Standards Institute and are revised by the European Committee on Antimicrobial Susceptibility Testing for epidemiological cut-off values. Innate resistance is due to multiple resistance mechanisms involving efflux pumps, inactivating enzymes, and low drug-target affinity. In addition, MAB may display acquired resistance to macrolides and amikacin through mutations in drug binding sites. Treatment outcomes are better for macrolide-based combinations and MAB subspecies massiliense. New compounds in the family of cyclines, oxazolidinones, and penem-β-lactamase inhibitor combinations (described in another paper), as well as bedaquiline, a new antituberculous agent, are promising, but their efficacy remains to be proven. PK/PD studies, which are critical for establishing optimal dosing regimens, were mainly done for monotherapy and healthy individuals.

IMPLICATIONS

Medical evidence is poor, and randomized clinical trials or standardized cohorts are needed to compare outcomes of patients with similar underlying disease, clinical characteristics, and identified MAB subspecies/sequevar. Microbiological diagnosis and susceptibility testing need to be harmonized to enable the comparison of agents and the testing of new compounds. Testing antimicrobial combinations requires new methods, especially for PK/PD parameters. Molecular testing may help in assessing MAB resistance prior to treatment. New antimicrobials need to be systematically tested against MAB to find an effective antimicrobial regimen.

Bedaquiline for treatment of non-tuberculous mycobacteria (NTM): a systematic review and meta-analysis

BACKGROUND

Non-tuberculous mycobacteria (NTM) infections are increasing in incidence and associated mortality. NTM are naturally resistant to a variety of antibiotics, complicating treatment. We conducted a literature assessment on the efficacy of bedaquiline in treating NTM species in vitro and in vivo (animal models and humans); meta-analyses were performed where possible.

METHOD

Four databases were searched using specific terms. Publications were included according to predefined criteria. Bedaquiline's impact on NTM in vitro, MICs and epidemiological cut-off (ECOFF) values were evaluated. A meta-analysis of bedaquiline efficacy against NTM infections in animal models was performed. Culture conversion, cure and/or relapse-free cure were used to evaluate the efficacy of bedaquiline in treating NTM infection in humans.

RESULTS

Fifty studies met the inclusion criteria: 33 assessed bedaquiline's impact on NTM in vitro, 9 in animal models and 8 in humans. Three studies assessed bedaquiline's efficacy both in vitro and in vivo. Due to data paucity, an ECOFF value of 0.5 mg/mL was estimated for Mycobacterium abscessus only. Meta-analysis of animal studies showed a 1.86× reduction in bacterial load in bedaquiline-treated versus no treatment within 30 days. In humans, bedaquiline-including regimens were effective in treating NTM extrapulmonary infection but not pulmonary infection.

CONCLUSIONS

Bedaquiline demonstrated strong antibacterial activity against various NTM species and is a promising drug to treat NTM infections. However, data on the genomic mutations associated with bedaquiline resistance were scarce, preventing statistical analyses for most mutations and NTM species. Further studies are urgently needed to better inform treatment strategies.

[A pharmacologic approach to treatment of Mycobacterium abscessus pulmonary disease]

Mycobacterium abscessus is a fast-growing non-tuberculous mycobacteria complex causing pulmonary infections, comprising the subspecies abscessus, massiliense and bolletii. Differences are based predominantly on natural inducible macrolide resistance, active in most Mycobacterium abscessus spp abscessus species and in Mycobacterium abscessus spp bolletii but inactive in Mycobacterium abscessus spp massiliense. Therapy consists in long-term treatment, combining multiple antibiotics. Prognosis is poor, as only 40% of patients experience cure. Pharmacodynamic and pharmacokinetic data on M. abscessus have recently been published, showing that therapy ineffectiveness might be explained by intrinsic bacterial resistance (macrolides…) and by the unfavorable pharmacokinetics of the recommended antibiotics. Other molecules and inhaled antibiotics are promising.

Skin and soft tissue infections due to rapidly growing mycobacteria

PURPOSE OF REVIEW

The aim of this article is to review skin and soft tissue infections due to rapidly growing mycobacteria (RGM), with a particular focus on recently published literature (2021-2022).

RECENT FINDINGS

RGM are increasingly reported as a cause of skin and soft tissue infections, both in the community setting and as a cause of nosocomial outbreaks. Recent advances in molecular methods have expanded the number of species of RGM and resulted in increased diagnosis. New treatment options are under evaluation particularly for Mycobacterium abscessus , the most difficult-to-treat among RGM.

SUMMARY

RGM are an uncommon cause of skin and soft tissue infections and a high clinical suspicion together with advanced laboratory facilities are required for diagnosis. Species identification and antimicrobial susceptibility testing are essential to drive appropriate treatment, which combines surgical debridement with prolonged antimycobacterial combination therapy.

Antimicrobial Susceptibility Testing Using the MYCO Test System and MIC Distribution of 8 Drugs against Clinical Isolates of Nontuberculous Mycobacteria from Shanghai

Given the increased incidence and prevalence of nontuberculous mycobacterial (NTM) diseases and the natural resistance of NTM to multiple antibiotics, in vitro susceptibility testing of different NTM species against drugs from the MYCO test system and new applied drugs is required. A total of 241 NTM clinical isolates were analyzed, including 181 slowly growing mycobacteria (SGM) and 60 rapidly growing mycobacteria (RGM). The Sensititre SLOMYCO and RAPMYCO panels were used for testing susceptibility to commonly used anti-NTM antibiotics. Furthermore, MIC distributions were determined against 8 potential anti-NTM drugs, including vancomycin (VAN), bedaquiline (BDQ), delamanid (DLM), faropenem (FAR), meropenem (MEM), clofazimine (CLO), cefoperazone-avibactam (CFP-AVI), and cefoxitin (FOX), and epidemiological cutoff values (ECOFFs) were analyzed using ECOFFinder. The results showed that most of the SGM strains were susceptible to amikacin (AMK), clarithromycin (CLA), and rifabutin (RFB) from the SLOMYCO panels and BDQ and CLO from the 8 applied drugs, while RGM strains were susceptible to tigecycline (TGC) from the RAPMYCO panels and also BDQ and CLO. The ECOFFs of CLO were 0.25, 0.25, 0.5, and 1 μg/mL for the mycobacteria M. kansasii, M. avium, M. intracellulare, and M. abscessus, respectively, and the ECOFF of BDQ was 0.5 μg/mL for the same four prevalent NTM species. Due to the weak activity of the other 6 drugs, no ECOFF was determined. This study on the susceptibility of NTM includes 8 potential anti-NTM drugs and a large sample size of Shanghai clinical isolates and demonstrates that BDQ and CLO had efficient activities against different NTM species in vitro, which can be applied to the treatment of NTM diseases. IMPORTANCE We designed customized panel that contains 8 repurposed drugs, including vancomycin (VAN), bedaquiline (BDQ), delamanid (DLM), faropenem (FAR), meropenem (MEM), clofazimine (CLO), cefoperazone-avibactam (CFP-AVI), and cefoxitin (FOX) from the MYCO test system. To better understand the efficacy of these 8 drugs against different NTM species, we determined the MICs of 241 NTM isolates collected in Shanghai, China. We attempted to define the tentative epidemiological cutoff values (ECOFFs) for the most prevalent NTM species, which is an important factor in setting up the breakpoint for a drug susceptibility testing. We used the MYCO test system as an automatic quantitative drug sensitivity test of NTM and extended the method to BDQ and CLO in this study. The MYCO test system complements commercial microdilution systems that currently lack BDQ and CLO detection.

Epidemiology of Nontuberculous Mycobacteria in Nanjing and MAB_0540 Mutations Associated with Clofazimine Resistance in Mycobacterium abscessus

Background

Nontuberculous mycobacteria (NTM) are easily misdiagnosed as multidrug-resistant tuberculosis (MDR-TB), and treatment drugs are very limited. The main objective of our study was to evaluate the minimal inhibitory concentration (MIC) in vitro of bedaquiline (BDQ), clofazimine (CFZ), linezolid (LZD), delamanid (DLM), and pretomanid (PA-824) for treatment of M. abscessus and M. intracellulare. Furthermore, we determined whether MAB_1448, MAB_4384, MAB_2299c, MAB_1483, MAB_0540, rplD, rplC, and rrl were related to drug resistance to provide an experimental basis for the use of these five drugs in the treatment of NTM.

Methods

We identified sample characteristics of epidemics in 550 patients with suspected NTM infection in Nanjing from 2019 to 2021 using the PCR-reverse spot hybrid method. Furthermore, we evaluated the MIC of BDQ, CFZ, DLM, LZD, and PA-824 against 155 clinical isolates of NTM using the microbroth dilution method. The resistant isolates were sequenced using Sanger sequencing.

Results

The top three dominant species of NTM distributed in Nanjing were M. intracellulare, M. avium, and M. abscessus. Notably, the proportion of M. abscessus infections increased. The proportion of M. abscessus increased from 12% in 2019 to 18% in 2021. Demographic analysis showed that female infection rates were substantialy greater than male for M. abscessus (P=0.017, <0.05). Our results demonstrate that NTM are highly sensitive to bedaquiline and clofazimine in vitro. However, delamanid and pretomanid had little effect on M. abscessus and M. intracellulare. In addition, we found 30-41 nucleotide deletion mutations and some novel point mutations in the MAB_0540 gene of M. abscessus that are resistant to clofazimine.

Conclusion

Bedaquiline, clofazimine, and linezolid were more successful in vitro treatments against M. abscessus and M. intracellulare. The MAB_0540 mutation may be associated with resistance of M. abscessus to clofazimine.