Meta-analyses and the evidence base for microbial outcomes in the treatment of pulmonary Mycobacterium avium-intracellulare complex disease

Ertapenem's therapeutic potential for Mycobacterium avium lung disease in the hollow fiber model

INTRODUCTION

Guideline-based therapy for Mycobacterium avium complex (MAC) pulmonary disease achieves sustained sputum conversion rates in only 43-53% of patients. Repurposing of β-lactam antibiotics such as ertapenem could expedite design of more efficacious regimens, compared to developing new drugs.

METHODS

We performed an ertapenem exposure-response study in the hollow fiber system model of intracellular MAC (HFS-MAC). We recapitulated human-like intrapulmonary concentration-time profiles of eight once-daily intravenous doses of ertapenem over 28 days and performed repetitive sampling for drug concentration-time profiles and MAC burden. The % of time concentration persisted above MIC (%TMIC) mediating either 50% or 80% of maximal effect (E50, EC80) were identified. The EC80 was used as target exposure in a 10,000 subject Monte Carlo experiments for ertapenem doses of 1G, 2G, or 4G administered once versus twice daily.

RESULTS

The ertapenem MIC ranged from 0.5 to 2 mg/L on three occasions. Ertapenem achieved a half-life of 4.04±0.80h in the HFS-MAC and killed a maximum of 2.17 log10 CFU/mL below day 0. The EC50 was %TMIC of 75.9% (95% confidence interval: 68.43% to 86.54%) and the EC80 was %TMIC of 100%. Target attainment probability was >90% for 1G twice daily up to an MIC of 2 mg/L, while for 2G twice daily the susceptibility MIC breakpoint was 4-8 mg/L.

CONCLUSIONS

Ertapenem microbial kill below day 0 burden was better than guideline-based therapy drugs in the HFS-MAC in the past. Ertapenem is a promising drug for novel combination therapies for MAC lung disease.

Prevalence and trends of hepatitis B and C virus biomarkers in Zimbabwe: comparative analyses of a nation's blood-donor surveillance data and meta-analyses of population studies

BACKGROUND

The disproportionate burden of viral hepatitis, particularly hepatitis B virus (HBV) is experienced by people living in low-resourced sub-Saharan Africa, where the estimated prevalence is 3-7 times the global average. Therefore to inform policy, we describe the seroprevalence and trends of hepatitis C (HCV) and HBV biomarkers: anti-HCV antibody and hepatitis B surface antigen (HBsAg), respectively, in Zimbabwe.

METHODS

We analysed data from 181,248 consecutive blood-donors, examined between January 2015 through December 2018. Additionally, we conducted a comprehensive literature review using PubMed and African Journals Online databases, meta-analysing selected papers from Zimbabwe, published between 1970 and 2020, that met specific criteria.

RESULTS

Overall age-standardized prevalence rate (ASPR) for anti-HCV was 8.67 (95%CI, 0.25-17.09) per 100,000, while that for HBsAg was 2.26 (95%, 1.89-2.63) per 1000 blood-donors, per year. Meta-analysis of 9 studies comprising 220,127 persons tested for anti-HCV revealed ASPR of 0.05% (95% 0%-0.19%) in blood-donors and 1.78% (95%CI, 0.01%-5.55%) in the general population, for an overall pooled ASPR of 0.44 (95%CI, 0.19%-0.76%). 21 studies comprising 291,784 persons tested for HBsAg revealed ASPR of 0.65% (95%CI, 0.31%-1.00%) in blood-donors and 4.31% (95%CI, 1.77%-6.50%) in the general population for an overall pooled ASPR of 4.02% (95%CI, 3.55%-4.48%), after HBV vaccine introduction. HBsAg prevalence was significantly higher before HBV vaccine introductions.

CONCLUSIONS

The prevalence of HBV is decreasing, consistent with the introduction of HBV vaccination, while HCV prevalence is increasing in Zimbabwe. This highlights the need for Improved blood-donor screening and more informative biomarker studies, particularly among repeat donors and children.

Omadacycline drug susceptibility testing for non-tuberculous mycobacteria using oxyrase to overcome challenges with drug degradation

BACKGROUND

Drug susceptibility testing (DST) protocol of omadacycline against non-tuberculous mycobacteria has not yet been established. We developed a method to accurately determine MIC omadacycline MIC against Mycobacterium abscessus (Mab), Mycobacterium avium-complex (MAC), and Mycobacterium kansasii (Mkn).

METHODS

First, we identified the oxyrase concentration not affecting Mab, MAC, and Mkn growth followed by omadacycline MIC experiments with and without oxyrase using reference and clinical strains.

RESULTS

Oxyrase 0.5 % (v/v) stabilized omadacycline in the culture medium. The median omadacycline MIC was 1 mg/L for Mab and 8 mg/L for Mkn. For MAC, the median omadacycline MIC was 2 mg/L for M. avium, 256 mg/L for M. intracellulare, and 4 mg/L for M. chimaera (p < 0.0001). Wilcoxon matched-pairs signed rank test revealed statistically lower MICs with oxyrase for all MAC subspecies (p < 0.0001), all Mab subspecies (p < 0.0001), and Mkn (p = 0.0002). The decrease in MICs with oxyrase was 17/18 of Mab, 14/19 of Mkn, 8/8 of M. avium, 4/5 M. chimera, but only 11/18 of M. intracellulare (p < 0.013).

CONCLUSION

Use of 0.5 % oxyrase could be a potential solution to reliable and reproducible omadacycline MIC of Mab. However, oxyrase demonstrated a variable effect in reducing MICs against MAC and Mkn.

Effect of multidrug therapy on the prognosis of Mycobacterium avium complex pulmonary disease

Multidrug therapy for Mycobacterium avium complex pulmonary disease (MAC-PD) results in negative sputum cultures. However, the prognostic value of this treatment approach remains unclear. This study aimed to clarify whether multidrug therapy reduces the incidence of events related to MAC-PD and improves the mortality rate. Patients who met the diagnostic criteria for MAC-PD at our hospital between 2003 and 2019 were retrospectively evaluated using medical records. Events related to MAC-PD were defined as hospitalisation for haemoptysis or respiratory infection and the development of chronic respiratory failure. There were 90 and 108 patients in the multidrug and observation groups, respectively. The median observation period was 86 months. Intergroup differences in body mass index, proportion of patients with cavities, and erythrocyte sedimentation rate were not significant. However, the observation group was older with a higher mean age (multidrug group: 62 years, observation group: 69 years; P < 0.001) and had a higher proportion of male patients (multidrug group: 13/90 [14.4%], observation group: 35/108 [32.4%]; P < 0.01). Furthermore, intergroup differences in the incidence of events related to MAC-PD (multidrug group: 26.69/1000 person-years, observation group: 25.49/1000 person-years), MAC-PD-associated mortality rate (multidrug group: 12.13/1000 person-years, observation group: 12.74/1000 person-years), and total mortality (multidrug group: 24.26/1000 person-years, observation group: 29.50/1000 person-years) were not significant. Many patients relapse even after multidrug therapy, and our findings suggest that multidrug therapy has no effect in preventing the onset of respiratory events or prolonging life expectancy.

In Vitro Evaluation of Drug-Drug Interaction Potential of Epetraborole, a Novel Bacterial Leucyl-tRNA Synthetase Inhibitor

Epetraborole (EBO) is a boron-containing inhibitor of bacterial leucyl-tRNA synthetase, with potent activity against nontuberculous mycobacteria (NTM) and Gram-negative bacteria, including Burkholderia pseudomallei. EBO is being developed for the treatment of NTM lung disease and melioidosis, administered in combination with other therapeutic agents in both diseases. Therefore, EBO and its major circulating metabolite M3 were evaluated in comprehensive drug-drug interaction (DDI) in vitro studies. The CYP inhibitory and substrate potential of EBO and M3 were assessed using hepatic microsomes. Stably transfected cells that expressed individual efflux or uptake transporters were used to determine whether EBO or M3 were substrates or inhibitors for these receptors. Stability studies indicated that EBO is a poor substrate for major CYP enzymes. Neither EBO nor M3 was a potent reversible or time-dependent inhibitor of major CYP enzymes. EBO was not an inducer of CYP1A2 mRNA, while it was a weak inducer of CYP2B6 and CYP3A4. EBO was a substrate only for OCT2. At clinically relevant concentrations, neither EBO nor M3 inhibited major human efflux or uptake transporters. Based on these data, at clinically relevant concentrations of EBO and M3, there is a low risk of victim or perpetrator DDI.

Sarecycline pharmacokinetics/pharmacodynamics in the hollow-fibre model of Mycobacterium avium complex: so near and yet so far

BACKGROUND

Poor sustained sputum culture conversion rates with the standard-of-care therapy highlight the need for better drugs to treat Mycobacterium avium complex pulmonary disease (MAC-PD).

OBJECTIVE

To determine the pharmacokinetics/pharmacodynamics (PK/PD)-optimized exposure of sarecycline and its potential role in treating MAC-PD.

METHODS

We performed MIC studies with MAC ATCC 700898 and 19 clinical isolates and test-tube static concentration-response studies. A dynamic hollow-fibre system model of intracellular MAC (HFS-MAC) study was performed mimicking six human-equivalent sarecycline dose concentration-time profiles to identify the PK/PD optimal exposure of sarecycline for MAC kill. The inhibitory sigmoid maximal effect (Emax) model was used for PK/PD analysis.

RESULTS

The sarecycline MIC of MAC ATCC 700898 was 1 mg/L, while the MIC for the 19 clinical strains ranged between 32 and >256 mg/L. The concentration mediating 50% of Emax (EC50) was similar between intracellular and extracellular MAC. In the HFS-MAC, all six sarecycline doses killed intracellular MAC, with an Emax of 1.0 log10 cfu/mL below Day 0 burden (stasis). The sarecycline EC80 (optimal) exposure was identified as AUC0-24/MIC = 139.46.

CONCLUSIONS

Sarecycline demonstrated anti-MAC Emax in the HFS-MAC model better than ethambutol but worse than omadacycline (>5 log10 cfu/mL below stasis) in HFS-MAC. However, since currently approved highest oral sarecycline dose achieves an AUC0-24 of 48.2 mg·h/L and MAC MICs are >32 mg/L, the target AUC0-24/MIC of 139.46 is unlikely to be achieved in patients.

The Clinical Implications of Serum Carbohydrate Antigen 19-9 Levels in Patients with Nontuberculous Mycobacteria Pulmonary Disease

Serum carbohydrate antigen 19-9 (CA19-9) levels can increase in nontuberculous mycobacteria pulmonary disease (NTM-PD), and the levels correlate with disease activity. We compared the clinical characteristics of NTM-PD patients with and without elevated CA19-9 levels and evaluated its association with antibiotic response in a retrospective study of NTM-PD patients diagnosed between January 1994 and December 2020. We analyzed 1112 patients who had serum CA19-9 measured: 322 with elevated CA19-9 and 790 with normal CA19-9. The erythrocyte sedimentation rate and C-reactive protein levels were significantly higher in the elevated CA19-9 group (p < 0.001 and p = 0.029, respectively). The 1-year culture conversion rate after antibiotics did not differ between the elevated (n = 206) and normal (n = 377) CA19-9 groups (80% vs. 72%, p = 0.055). Analysis of a subset of 434 patients revealed that current smoking, bronchiectasis, acid-fast bacilli smear positivity, and the M. abscessus strain significantly reduced microbiological cure rates. Serum CA 19-9 levels did not have a significant association with microbiological cure in a multivariate analysis. These findings suggest that the role of serum CA19-9 in predicting antibiotic treatment outcomes is limited, and that elevated CA19-9 does not necessarily indicate a poor outcome.

Treatment of Mycobacterium avium Complex Pulmonary Disease: When Should I Treat and What Therapy Should I Start?

Treatment of M avium pulmonary disease requires a three-drug, macrolide-based regimen that is administered for 12 months beyond culture conversion. The regimen can be administered 3 days a week in non-cavitary, nodular bronchiectatic disease but should be given daily when cavitary disease is present. For treatment refractory disease, amikacin liposome inhalation suspension is added to the regimen. Parenteral amikacin or streptomycin should be administered in the setting of extensive radiographic involvement or macrolide resistance. Recurrence of disease is common and often due to reinfection. Novel and repurposed agents are being evaluated in clinical trials.

Spontaneous Cultural Conversion Rate of Mycobacterium avium Complex Pulmonary Disease Based on BACES Severity

BACKGROUND

Only a few clinical factors can aid in predicting spontaneous culture conversion (SCC) in patients with Mycobacterium avium complex-pulmonary disease (MAC-PD). In this study, we aimed to evaluate whether the rate of SCC varies according to the severity of the disease in MAC-PD patients.

METHODS

We retrospectively classified 373 MAC-PD patients who had undergone watchful waiting without antibiotics based on the severity assessment using the 'body mass index (BMI), age, cavity, erythrocyte sedimentation rate (ESR), and sex (BACES)' criteria. We evaluated the rate of SCC in MAC-PD patients based on BACES severity and analyzed the relevant factors. Results: Of 373 patients, 153 (41%) achieved SCC without antibiotics during a median follow-up of 48.1 months. There was a trend toward a higher SCC rate in patients with lower BACES severity: 48% (87/183), 37% (58/157), and 24% (8/33) in the mild, moderate, and severe BACES groups, respectively. In addition, a favorable outcome, defined as maintaining SCC or having two consecutive negative sputum cultures until the last follow-up date, was also more common in patients with lower BACES severities of 53% (97/183), 34% (54/157), and 18% (6/33) in the mild, moderate, and severe BACES groups, respectively. In multivariate analysis, moderate BACES (hazard ratio [HR] = 0.63; 95% confidence interval [CI] 0.44-0.91; p = 0.013) and severe BACES (HR 0.37; 95% CI 0.16-0.90; p = 0.028) had a significantly negative impact on favorable outcomes compared to mild BACES.

CONCLUSIONS

Lower BACES severity may be associated with SCC in MAC-PD patients.

Changes in sputum microbiota during treatment for nontuberculous mycobacterial pulmonary disease

Limited data exist on longitudinal changes in the sputum bacterial microbiome during treatment in nontuberculous mycobacterial pulmonary disease (NTM-PD) patients. We prospectively collected serial sputum samples from 14 NTM-PD patients during treatment, at the start (n = 14) and at 1 (n = 10), 3 (n = 10), 6 (n = 12), and 12 (n = 7) months. The bacterial microbiome changes were analyzed using 16S rRNA sequences (V3-V4 regions). Subgroup analysis included culture conversion (n = 9) and treatment refractory (n = 5) groups. In all patients, sputum alpha-diversity (ACE, Chao1, and Jackknife) significantly decreased during antibiotic treatment at 1, 3, 6, and 12 months compared to treatment initiation levels. Within the culture conversion group, genus/species-level beta-diversity showed differences at 1, 3, 6, and 12 months compared to treatment initiation (all p < 0.05). However, in the refractory group, there were no differences in beta-diversity at the genus/species levels in the sputum at any time point. In the linear discriminant analysis (LDA) effect sizes (LEfSe) analysis, the culture conversion group exhibited decreasing taxa at various levels (phylum/genus/species), but no significant increase in taxa was observed. LEfSe analysis of the refractory patient group revealed multiple taxa decreased during treatment. However, proportions of Veillonella dispar (LDA = 4.78), Fusobacterium periodonticum (LDA = 4.35), and Pseudomonas aeruginosa (LDA = 2.92) increased as the treatment period progressed in the refractory group. Sputum microbiota diversity decreases during NTM-PD treatment. In the culture conversion group, most taxa decrease, while some increase in the refractory group. These findings suggest that a distinct respiratory microbial community may exist in refractory NTM-PD patients compared to responsive antibiotic-treated patients.

Additive Effects of Cyclic Peptide [R4W4] When Added Alongside Azithromycin and Rifampicin against Mycobacterium avium Infection

Mycobacterium avium (M. avium), a type of nontuberculous mycobacteria (NTM), poses a risk for pulmonary infections and disseminated infections in immunocompromised individuals. Conventional treatment consists of a 12-month regimen of the first-line antibiotics rifampicin and azithromycin. However, the treatment duration and low antibiotic tolerability present challenges in the treatment of M. avium infection. Furthermore, the emergence of multidrug-resistant mycobacterium strains prompts a need for novel treatments against M. avium infection. This study aims to test the efficacy of a novel antimicrobial peptide, cyclic [R4W4], alongside the first-line antibiotics azithromycin and rifampicin in reducing M. avium survival. Colony-forming unit (CFU) counts were assessed after treating M. avium cultures with varying concentrations of cyclic [R4W4] alone or in conjunction with azithromycin or rifampicin 3 h and 4 days post-treatment. M. avium growth was significantly reduced 4 days after cyclic [R4W4] single treatment. Additionally, cyclic [R4W4]-azithromycin and cyclic [R4W4]-rifampicin combination treatments at specific concentrations significantly reduced M. avium survival 3 h and 4 days post-treatment compared with single antibiotic treatment alone. These findings demonstrate cyclic [R4W4] as a potent treatment method against M. avium and provide insight into novel therapeutic approaches against mycobacterium infections.

Omadacycline pharmacokinetics/pharmacodynamics in the hollow fiber model and clinical validation of efficacy to treat pulmonary Mycobacterium abscessus Disease

BACKGROUND

Guideline-based therapy for pulmonary Mycobacterium abscessus (Mab) disease achieves sustained sputum culture conversion (SSCC) rates of 30%, a fact reflected by poor efficacy of GBT in the hollow fiber system model of Mab (HFS-Mab) which killed ∼1.22 log10 CFU/mL. This study was performed to determine what clinical dose of omadacycline, a tetracycline antibiotic, should be used in combination therapy to treat pulmonary Mab disease for relapse free cure.

METHODS

First, we mimicked omadacycline intrapulmonary concentration-time profiles of seven daily doses in the HFS-Mab model and identified exposures associated with optimal efficacy. Second, we determined if oral omadacycline 300mg/day would achieve these optimal exposures in 10,000 subject Monte-Carlo simulations. Third, we performed a retrospective clinical study for rates of SSCC and toxicity, on omadacycline versus primarily tigecycline-based salvage therapy. Fourth, a single patient was recruited to validate the findings.

RESULTS

Omadacycline efficacy in the HFS-Mab was 2.09 log10 CFU/mL at exposures achieved in >99% of patients on 300mg/day omadacycline. In the retrospective study, SSCC with omadacycline 300mg/day-based combinations was achieved in 8/10 versus 1/9 (p=0.006), symptom improvement in 8/8 versus 5/9 (p=0.033), toxicity in 0 versus 9/9 (p<0.001), and therapy discontinuation due to toxicity in 0 versus 3/9 (p<0.001) of cases versus comparators, respectively. In one prospectively recruited patient, omadacycline 300mg/day salvage therapy achieved SSCC and symptom-resolution in 3-months.

CONCLUSION

Based on the preclinical and clinical data, omadacycline dose of 300mg/day in combination regimens could be appropriate for testing in phase III trials in patients with Mab pulmonary disease.

Healthcare use and medical cost before and after diagnosis of nontuberculous mycobacterial infection in Korea: the National Health Insurance Service-National Sample Cohort Study

BACKGROUND AND OBJECTIVE

The global prevalence and incidence of nontuberculous mycobacterial (NTM) infections are increasing; however, population-level data on healthcare use and medical costs for people with NTM infections are limited. Thus, we investigated the rates of healthcare use and medical costs of people with NTM infections in South Korea using the National Health Insurance Service-National Sample Cohort from 2002 to 2015.

METHODS

In this cohort study, people with and without NTM infection aged 20-89 years were matched 1 to 4 by sex, age, Charlson comorbidity index, and year of diagnosis. The overall and annual average healthcare use and medical costs were calculated. In addition, trends in healthcare use and medical costs for each of the 3 years before and after NTM diagnosis were investigated for people diagnosed with NTM infection.

RESULTS

A total of 798 individuals (336 men and 462 women) diagnosed with NTM infection and 3192 controls were included in the study. NTM-infected patients had significantly higher rates of healthcare use and medical costs than those in the control group (p < 0.05). NTM-infected patients showed 1.5 times the medical cost and 4.5 times the respiratory disease cost of the control group. People diagnosed with NTM infection incurred the highest medical costs in the 6 months before diagnosis.

CONCLUSION

NTM infection increases the economic burden on Korean adults. Appropriate diagnostic tests and treatment plans for NTM infections are needed to reduce the burden of the disease caused by such infection.

Nontuberculous mycobacteria isolation from sputum specimens: A retrospective analysis of 1061 cases

Background

In recent years, with the development of laboratory methods, the frequency of nontuberculosis mycobacteria (NTM) infections has increased. The primary aim of this study was to evaluate the clinical significance of therapeutic drug monitoring (TDM) growths in respiratory samples, and the secondary aim was to evaluate the treatment regimens and treatment outcomes of treatment for TDM disease.

Methods

This study was a retrospective cohort study. Persons with NTM growth in respiratory samples admitted to the reference hospital between 2009 and 2020 were included in this study. Samples detected as NTM by the immunochromatographic rapid diagnostic test, those requested by the clinicians, species were determined by the hsp65PCRREA method. The subjects were classified into 3 groups: patients with NTM infection who received treatment (135, 12.7%), those followed up without treatment (690, 65.1%), and a last group of patients with Mycobacterium tuberculosis (TB) complex strains were isolated and received TB treatment (236, 22.2%). Initiating NTM treatment was decided in accordance with the American Thoracic Society recommendations.

Results

The mean ± standard deviation age of patients was 53.8 ± 16.5 years, and 749 (70.6%) were male. In total, 278 (26.2%) out of 1061 cases had identified, and the most frequent species were MAC (81; Mycobacterium avium: 39, Mycobacterium intracellulare: 39, and MAC: 3), Mycobacterium abscessus (67), Mycobacterium kansasii (48), Mycobacterium fortuitum (23), Mycobacterium chelonae (12), Mycobacterium gordonae (11), and Mycobacterium szulgai (11). In the NTM treatment group, 116 (85.9%) of 135 patients had multiple culture positivity. Previous TB treatment history had 51 (37.8%) of 135 patients, respiratory comorbidities were evident in 37 (27.4%) of 135 patients. Thorax computed tomography imaging in 84 patients revealed nodule 38 (45.2%), consolidation 46 (54.8%), cavity 52 (61.9%), and bronchiectasis 27 (32.1%). Treatment results in the NTM treatment group were as follows: ongoing treatment 14 (10.4%), cure 64 (47.4%), default 33 (24.4%), exitus 19 (14.1%), recurrence 3 (2.2%), and refractory disease 2 (1.5%).

Conclusion

This is a large case series evaluating the clinical significance of NTM growths and NTM treatment in Turkey. The clinical significance of NTM growth in respiratory samples is low. Treatment success rates of NTM patients who are treated are low. Treatment defaults and mortality rates are high. New drugs and new regimens are needed.

Antibiotic Maintenance and Redevelopment of Nontuberculous Mycobacteria Pulmonary Disease after Treatment of Mycobacterium avium Complex Pulmonary Disease

Limited data are available regarding the impact of the antibiotic maintenance period on the redevelopment of nontuberculous mycobacteria-pulmonary disease (NTM-PD) after microbiological cure of Mycobacterium avium complex (MAC)-PD. This retrospective study included 631 MAC-PD patients who achieved microbiological cure between 1994 and 2021. Data on the antibiotic maintenance period, defined as the time between culture conversion and treatment completion, were collected. Redevelopment, the subsequent diagnosis of NTM-PD regardless of causative organism after microbiological cure, was investigated. Factors associated with redevelopment were analyzed after adjusting for disease severity using the body mass index, age, cavity, erythrocyte sedimentation rate, and sex (BACES) scoring system. In total, 205 (33%) patients experienced redevelopment, with a median maintenance period after culture conversion of 15.0 months (interquartile range, 13.0 to 22.0 months). A greater proportion of patients with the nodular bronchiectatic form of MAC-PD (87% versus 80%, P = 0.033) and a longer maintenance period (median 15.0 versus 14.0 months, P < 0.001) were noted in the redevelopment group compared with the nonredevelopment group. The cumulative rate of redevelopment according to the maintenance period did not differ between the >12-month and ≤12-month groups in the total patient population or the subgroups sorted according to BACES severity. No association between a maintenance period >12 months and redevelopment was identified in multivariate models. Extending the antibiotic maintenance period more than 12 months did not reduce the redevelopment rate even with adjustment for disease severity, suggesting the need to further optimize the duration of the antibiotic maintenance period.

IMPORTANCE Limited data are available regarding the impact of the antibiotic maintenance period on the redevelopment of Mycobacterium avium complex-pulmonary (MAC-PD) disease after microbiological cure. To improve treatment outcomes and reduce the recurrence rate, current guidelines recommend maintenance of antibiotics for a minimum of 12 months after achievement of negative culture conversion. However, the optimal duration of antibiotic therapy for MAC-PD is not currently known. Moreover, in real-world clinical practice, total antibiotic duration is mainly impacted by the length of the maintenance period; however, it is unknown whether extending the maintenance period is beneficial for preventing redevelopment of NTM-PD. Our study may help to address concerns regarding the antibiotic maintenance period after achievement of negative culture conversion in patients with MAC-PD.

Treatment outcomes of Mycobacterium avium complex pulmonary disease according to disease severity

Mycobacterium avium complex pulmonary disease (MAC-PD) requires long-term treatment. We analyzed the outcomes of 992 MAC-PD patients according to disease severity and compared the outcomes of intermittent and daily therapy for mild disease. Patients were divided into groups according to severity using the body mass index, age, cavity, erythrocyte sedimentation rate, and sex (BACES) system, and culture conversion rates were evaluated. We also evaluated the effects of intermittent treatment on the culture conversion rates in mild disease group. Using the BACES, 992 patients were divided into mild (n = 331), moderate (n = 503), and severe (n = 158) disease groups, and culture conversion at the end of treatment was achieved in 85% (282/331), 80% (403/503), and 61% (97/158), respectively. Differences in culture conversion among the severity groups were significant (p < 0.001). In patients with mild disease, culture conversion rates were similar between intermittent (84%, 166/198) and daily (87%, 116/133) treatment (p = 0.396), and intermittent antibiotic therapy did not negatively impact culture conversion (adjusted hazard ratio 1.08; confidence interval 0.83–1.41; p = 0.578). MAC-PD patients with mild disease had higher culture conversion rates. Daily and intermittent therapy yielded similar culture conversion rates for mild disease. Treatment strategies with lower pill burden may be applicable in mild MAC-PD.

OUP accepted manuscript

Objectives

The standard of care (SOC) for the treatment of pulmonary Mycobacterium avium complex (MAC) disease (clarithromycin, rifabutin, and ethambutol) achieves sustained sputum conversion rates of only 54%. Thus, new treatments should be prioritized.

Methods

We identified the omadacycline MIC against one laboratory MAC strain and calculated drug half life in solution, which we compared with measured MAC doubling times. Next, we performed an omadacycline hollow fibre system model of intracellular MAC (HFS-MAC) exposure–effect study, as well as the three-drug SOC, using pharmacokinetics achieved in patient lung lesions. Data was analysed using bacterial kill slopes (γ-slopes) and inhibitory sigmoid E_max bacterial burden versus exposure analyses. Monte Carlo experiments (MCE) were used to identify the optimal omadacycline clinical dose.

Results

Omadacycline concentration declined in solution with a half-life of 27.7 h versus a MAC doubling time of 16.3 h, leading to artefactually high MICs. Exposures mediating 80% of maximal effect changed up to 8-fold depending on sampling day with bacterial burden versus exposure analyses, while γ-slope-based analyses gave a single robust estimate. The highest omadacycline monotherapy γ-slope was −0.114 (95% CI: −0.141 to −0.087) (r^2 =0.98) versus −0.114 (95% CI: −0.133 to −0.094) (r²= 0.99) with the SOC. MCEs demonstrated that 450 mg of omadacycline given orally on the first 2 days followed by 300 mg daily would achieve the AUC_0-24 target of 39.67 mg·h/L.

Conclusions

Omadacycline may be a potential treatment option for pulmonary MAC, possibly as a back-bone treatment for a new MAC regimen and warrants future study in treatment of this disease.

Impact of time between diagnosis and treatment for nontuberculous mycobacterial pulmonary disease on culture conversion and all-cause mortality

BACKGROUND

Limited data are available regarding when to start treatment following a diagnosis of nontuberculous mycobacteria-pulmonary disease (NTM-PD) or regarding how achieving culture conversion affects NTM-PD outcomes.

RESEARCH QUESTION

Does the time between diagnosis and antibiotic initiation influence culture conversion or all-cause mortality in NTM-PD, and is there any association between achieving culture conversion after antibiotics and reduced all-cause mortality?

STUDY DESIGN AND METHODS

We evaluated 712 patients who received antibiotics for ≥ 6 months after diagnosis of NTM-PD between July 1997 and December 2013. Data on the waiting period, defined as the time interval between diagnosis and treatment initiation, and on outcomes such as culture conversion by six months or death were collected. Factors associated with outcomes were analyzed after adjusting for disease severity using the body mass index, age, cavity, erythrocyte sedimentation rate and sex (BACES) system.

RESULTS

Thirty-eight percent of study patients had mild disease, 48% had moderate disease, and 14% had severe disease. The median waiting period without antibiotics among all patients was 4.8 (interquartile range 1.3-20.8) months. After treatment initiation, 479 (67%) patients achieved culture conversion within six months, whereas 135 (19%) patients died. In univariate and multivariate models adjusted for BACES severity, no association between the waiting period and 6-month culture conversion or death was identified. However, 6-month culture conversion demonstrated a significant negative correlation with death (crude hazard ratio [HR] 0.46, 95% confidence interval [CI] 0.33-0.65; adjusted HR 0.51, 95% 0.35-0.74). In the sub-group treated for ≥ 12 months, 12-month culture conversion was also associated with reduced death (adjusted HR 0.51, 95% CI 0.33-0.78).

INTERPRETATION

It may be reasonable to start antibiotics according to the 'watchful waiting' strategy for NTM-PD, but given the survival benefits, achieving culture conversion is an important goal for patients in need of treatment.

In Vitro Activity of Oxazolidinone against Nontuberculous Mycobacteria, Including Macrolide-Resistant Clinical Isolates

We evaluated the in vitro activities of oxazolidinone antibiotics, including linezolid, sutezolid, and delpazolid, against clinical nontuberculous mycobacteria (NTM) isolates. Regardless of macrolide resistance, for Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium kansasii, sutezolid showed the lowest MIC and minimal bactericidal concentration (MBC) values among oxazolidinone antibiotics. However, for Mycobacterium abscessus and Mycobacterium massiliense, the MIC and MBC for all oxazolidinone antibiotics showed similar values. Oxazolidinone antibiotics warrant further investigation as potential treatment for NTM.

Amikacin liposome inhalation suspension as a treatment for patients with refractory mycobacterium avium complex lung infection

Introduction: Amikacin liposome inhalation suspension (ALIS) contains amikacin sulfate, an aminoglycoside antibacterial drug. It has been approved in the US as a combined antibiotic treatment for refractory MAC lung disease patients. ALIS, as an inhaled antibiotic, can deliver amikacin to the infected site effectively and reduce systemic toxicity.Areas covered: This article gives a summated review of the pharmacodynamics, pharmacokinetics, therapeutic efficacy, post-marketing surveillance, and regulatory affairs of ALIS as an add-on therapy for MAC lung disease in adults by analyzing data from preclinical studies, clinical trials and original studies. We systematically searched Medline/PubMed through October 2020.Expert opinion: Studies demonstrate that ALIS as an add-on treatment significantly improve the rate of sputum culture conversion in MAC lung disease patients compare to guideline-recommended therapy only. The ALIS treatment showed a similar risk of serious adverse events and a low chance of renal adverse events. However, ALIS was associated with more respiratory adverse events than guideline-recommended therapy only. There was not sufficient data to conclude that ALIS treatment can improve clinical outcomes; however, with the significant improvement in the microbiology outcome in MAC lung disease patients, ALIS showed its potential use as an adjunct treatment for treating MAC lung disease.

Comparison of Rifamycins for Efficacy Against Mycobacterium avium Complex and Resistance Emergence in the Hollow Fiber Model System

Rifamycins are integral part of the combination regimen for treatment of pulmonary Mycobacterium avium-complex [MAC] infection, but different practitioners prefer different rifamycins. The objective of the study was to compare microbial kill and resistance emergence of rifamycins using principles of pharmacokinetics/pharmacodynamics. First, we identified rifamycin MICs in 20 MAC isolates from patients followed by concentration-response studies in test-tubes. Next, we examined efficacy and resistance suppression of three doses of each rifamycin in the hollow fiber system model of pulmonary MAC [HFS-MAC], mimicking human like concentration-time profile of the drugs. HFS-MAC units were repetitively sampled for total and drug-resistant MAC burden and for drug concentration measurements. Inhibitory sigmoid E max model, linear regression, and analysis of variance was used for data analysis. For rifabutin 90% of isolates had MIC ≤ 0.125 mg/L while for both rifampin and rifapentine this was ≤2.0 mg/L. There was no statistically significant difference (p > 0.05) in maximal kill and effective concentration mediating 50% of the bacterial kill among three rifamycins in the static concentration experiment. In the HFS-MAC, the bactericidal kill (day 0-4) for rifampin was 0.89 (95% Confidence Interval (CI): 0.43-1.35), for rifapentine was 1.05 (95% CI: 0.08-1.23), and for rifabutin was 0.92 (95% CI: 0.61-1.24) log10 CFU/ml, respectively. Rifamycins monotherapy failed after just 4-days of treatment and entire MAC population was drug resistant on day 26 of the study. There was no dose dependent difference in MAC kill or resistance suppression among the three rifamycins tested in the HFS-MAC. Therefore, replacing one rifamycin, due to emergence of drug-resistance, with other may not be beneficial in clinical setting.

Clinical risk factors related to treatment failure in Mycobacterium abscessus lung disease

The clinical importance of Mycobacterium abscessus subsp. abscessus (M. abscessus) lung disease has been increasing, but few studies have assessed the clinical characteristics associated with the treatment outcome. We retrospectively analyzed 75 consecutive patients with M. abscessus lung disease diagnosed at a tertiary hospital from January 2004 to April 2018. Among 52 patients with sufficient clinical data, 19 patients (42.2%) achieved treatment success. Compared with 26 (57.8%) patients in the treatment failure group, body mass index (BMI) (19.8 vs 17.5 kg/m2, P = 0.022), previous nontuberculous mycobacterial (NTM) lung disease (26.3% vs 61.5%, P = 0.034), the presence of cavitary lesions (31.6% vs 69.2%, P = 0.017), and the bronchiectasis score (3.0 vs 5.0, P = 0.003) were significantly different in the treatment success group. Multivariate analysis showed that age (adjusted hazard ratio (aHR), 0.94; 95% confidence interval (CI), 0.90 to 0.99; P = 0.010), the presence of cavitary lesions (aHR, 0.34; 95% CI, 0.12 to 0.94; P = 0.039), and previous NTM lung disease (aHR, 0.28; 95% CI, 0.09 to 0.86; P = 0.026) were negatively associated with treatment success. This is the first study to show that previous NTM lung disease might be a clinically important factor related to unfavorable treatment outcomes in M. abscessus lung disease patients. To increase our understanding the characteristics of M. abscessus lung disease, this factor should be independently analyzed in future research.

Lungenerkrankung durch nicht-tuberkulöse Mykobakterien

Die neue ATS/ERS/ESCMID/IDSA-Leitlinie beantwortet 22 PICO-Fragen zur Behandlung von Erkrankungen der Lunge durch Mycobacterium avium-Komplex (MAC), M. kansasii, M. xenopi und M. abscessus.

Allgemeines Insbesondere bei Patienten mit mikroskopischem Nachweis säurefester Stäbchen im Sputum oder kavernöser Verlaufsform sollte der Behandlungsbeginn nicht verzögert werden. Die Behandlung sollte auf einer speziesspezifischen Resistenztestung (entsprechend den CLSI-Guidelines) basieren.

MAC-Lungenerkrankung Die Therapie erfolgt hier mit mindestens 3 Medikamenten inklusive einem Makrolid (eher Azithromycin als Clarithromycin) und Ethambutol. Für Patienten mit kavitärer, mit ausgeprägter nodulär-bronchiektatischer Erkrankung oder mit Makrolid-Resistenz wird zur täglichen oralen Therapie eine additive Gabe von parenteralem Amikacin oder Streptomycin empfohlen. Liposomal verkapseltes inhalatives Amikacin wird bei Therapieversagen empfohlen. Patienten mit nodulär-bronchiektatischer Erkrankungsmanifestation sollten eine orale Makrolid-basierte Therapie, die – je nach Ausmaß – 3 ×/Woche gegeben werden kann, erhalten. Als Dauer werden 12 Monate nach Konversion der Sputumkultur empfohlen.

M. kansasii-Lungenerkrankung Empfohlen ist die Dreifachkombination aus Rifampicin, Ethambutol und Makrolid (oder Isoniazid ) für mindestens 12 Monate. Bei Rifampicin-Resistenz oder -unverträglichkeit wird Moxifloxacin als Ersatz empfohlen.

M. xenopi-Lungenerkrankung Empfohlen ist die Dreifachkombination aus Rifampicin, Ethambutol und Makrolid (oder Moxifloxacin) für mindestens 12 Monate nach Konversion der Sputumkultur. Es wird empfohlen, bei Patienten mit kavernöser Verlaufsform zumindest parenterales Amikacin zu addieren und Experten zu konsultieren.

M. abscessus-Lungenerkrankung Mindestens 3 Medikamente werden zur Therapie empfohlen. Die Substanzauswahl sollte auf einer In-vitro-Resistenztestung basieren. Makrolide sind die Grundlage, sollten aber bei Stämmen mit induzierbarer Makrolidresistenz nicht mitgerechnet werden. Zur Therapiedauer werden aufgrund fehlender Daten keine expliziten Empfehlungen ausgesprochen, eine Konsultation von Experten wird empfohlen.

Outcomes of Inhaled Amikacin and Clofazimine-Containing Regimens for Treatment of Refractory Mycobacterium avium Complex Pulmonary Disease

Limited data are available regarding optimal treatment for refractory Mycobacterium avium complex-pulmonary disease (MAC-PD). We evaluated outcomes of inhaled amikacin (AMK) with clofazimine (CFZ) regimens as an add-on salvage therapy for refractory MAC-PD. We retrospectively analyzed 52 patients with refractory MAC-PD, characterized by persistently positive sputum cultures despite >6 months of treatment. Thirty-five (67%) patients had M. intracellulare-PD, and 17 (33%) patients had M. avium-PD. Twenty-seven (52%) patients received the salvage therapy for ≥12 months, whereas 25 (48%) patients were treated for <12 months due to adverse effects or other reasons. Seventeen (33%) patients had culture conversion: 10 (10/27) in the ≥12-month treatment group and seven (7/25) in the <12-month treatment group (p = 0.488). Microbiological cure, defined as maintenance of culture negativity, was achieved in 12 (23%) patients; six (6/12) with accompanying symptomatic improvement were considered to have reached cure. Clinical cure, defined as symptomatic improvement with <3 consecutive negative cultures, was achieved in three (6%) patients. Overall, 15 (29%) patients achieved favorable outcomes, including microbiological cure, cure, and clinical cure. Inhaled AMK with CFZ may provide favorable outcomes in some patients with refractory MAC-PD. However, given the adverse effects, more effective strategies are needed to maintain these therapeutic regimens.

Epidemiology, diagnosis & treatment of non-tuberculous mycobacterial diseases

Non-tuberculous mycobacteria (NTM) are ubiquitously present in the environment, but NTM diseases occur infrequently. NTM are generally considered to be less virulent than Mycobacterium tuberculosis, however, these organisms can cause diseases in both immunocompromised and immunocompetent hosts. As compared to tuberculosis, person-to-person transmission does not occur except with M. abscessus NTM species among cystic fibrosis patients. Lung is the most commonly involved organ, and the NTM-pulmonary disease (NTM-PD) occurs frequently in patients with pre-existing lung disease. NTM may also present as localized disease involving extrapulmonary sites such as lymph nodes, skin and soft tissues and rarely bones. Disseminated NTM disease is rare and occurs in individuals with congenital or acquired immune defects such as HIV/AIDS. Rapid molecular tests are now available for confirmation of NTM diagnosis at species and subspecies level. Drug susceptibility testing (DST) is not routinely done except in non-responsive disease due to slowly growing mycobacteria ( M. avium complex, M. kansasii) or infection due to rapidly growing mycobacteria, especially M. abscessus. While the decision to treat the patients with NTM-PD is made carefully, the treatment is given for 12 months after sputum culture conversion. Additional measures include pulmonary rehabilitation and correction of malnutrition. Treatment response in NTM-PD is variable and depends on isolated NTM species and severity of the underlying PD. Surgery is reserved for patients with localized disease with good pulmonary functions. Future research should focus on the development and validation of non-culture-based rapid diagnostic tests for early diagnosis and discovery of newer drugs with greater efficacy and lesser toxicity than the available ones.

Treatment of Nontuberculous Mycobacterial Pulmonary Disease: An Official ATS/ERS/ESCMID/IDSA Clinical Practice Guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

Minocycline treatment for pulmonary Mycobacterium avium complex disease based on pharmacokinetics/pharmacodynamics and Bayesian framework mathematical models

OBJECTIVES

Our aim was to identify the pharmacokinetic/pharmacodynamic parameters of minocycline in the hollow-fibre system (HFS) model of pulmonary Mycobacterium avium complex (MAC) and to identify the optimal clinical dose.

METHODS

Minocycline MICs for 55 MAC clinical isolates from the Netherlands were determined. We also co-incubated primary isolated macrophages infected with MAC with minocycline. Next, we performed a 28 day HFS-MAC model dose-response study in which we mimicked pulmonary concentration-time profiles achieved in patients. The HFS-MAC model was sampled at intervals to determine the minocycline pharmacokinetics and MAC burden. We identified the AUC0-24/MIC ratios associated with 1.0 log10 cfu/mL kill below day 0 (stasis), defined as a bactericidal effect. We then performed 10000 Monte Carlo experiments to identify the optimal dose for a bactericidal effect in patients.

RESULTS

The MIC for 50% and 90% of cumulative clinical isolates was 8 and 64 mg/L, respectively. Minocycline decreased MAC bacterial burden below stasis in primary isolated macrophages. In the HFS-MAC model, minocycline achieved a microbial kill of 3.6 log10 cfu/mL below stasis. The AUC0-24/MIC exposure associated with a bactericidal effect was 59. Monte Carlo experiments identified a minocycline susceptibility MIC breakpoint of 16 mg/L. At this proposed breakpoint, the clinical dose of 200 mg/day achieved the bactericidal effect exposure target in ∼50% of patients, while 400 mg/day achieved this in 73.6% of patients, in Monte Carlo experiments.

CONCLUSIONS

Minocycline at a dose of 400 mg/day is expected to be bactericidal. We propose a clinical trial for validation.

Lungenerkrankung durch nicht-tuberkulöse Mykobakterien – Die neue ATS/ERS/ESCMID/IDSA-Leitlinie

Die neue ATS/ERS/ESCMID/IDSA-Leitlinie beantwortet 22 PICO Fragen zur Behandlung von Erkrankungen der Lunge durch Mycobacterium avium-Komplex (MAC), M. kansasii, M. xenopi und M. abscessus.

Allgemeines Insbesondere bei Patienten mit mikroskopischem Nachweis säurefester Stäbchen im Sputum oder kavernöser Verlaufsform sollte der Behandlungsbeginn nicht verzögert werden. Die Behandlung sollte auf einer speziesspezifischen Resistenztestung (entsprechend den CLSI-Guidelines) basieren.

MAC-Lungenerkrankung Die Therapie erfolgt hier mit mindestens 3 Medikamenten inklusive einem Makrolid (eher Azithromycin als Clarithromycin) und Ethambutol. Für Patienten mit kavitärer, mit ausgeprägter nodulär-bronchiektatischer Erkrankung oder mit Makrolid-Resistenz wird zur täglichen oralen Therapie eine additive Gabe von parenteralem Amikacin oder Streptomycin empfohlen. Liposomal verkapseltes inhalatives Amikacin wird bei Therapieversagen empfohlen. Patienten mit nodulär-bronchiektatischer Erkrankungsmanifestation sollten eine orale Makrolid-basierte Therapie, die – je nach Ausmaß – 3-mal/Woche gegeben werden kann, erhalten. Als Dauer werden 12 Monate nach Konversion der Sputumkultur empfohlen.

M. kansasii-Lungenerkrankung Empfohlen ist die Dreifachkombination aus Rifampicin, Ethambutol und Makrolid (oder Isoniazid) für mindestens 12 Monate. Bei Rifampicin-Resistenz oder -unverträglichkeit wird Moxifloxacin als Ersatz empfohlen.

M. xenopi-Lungenerkrankung Empfohlen ist die Dreifachkombination aus Rifampicin, Ethambutol und Makrolid (oder Moxifloxacin) für mindestens 12 Monate nach Konversion der Sputumkultur. Es wird empfohlen, bei Patienten mit kavernöser Verlaufsform zumindest parenterales Amikacin zu addieren und Experten zu konsultieren.

M. abscessus-Lungenerkrankung Mindestens 3 Medikamente werden zur Therapie empfohlen. Die Substanzauswahl sollte auf einer In-vitro-Resistenztestung basieren. Makrolide sind die Grundlage, sollten aber bei Stämmen mit induzierbarer Makrolidresistenz nicht mitgerechnet werden. Zur Therapiedauer werden aufgrund fehlender Daten keine expliziten Empfehlungen ausgesprochen, eine Konsultation von Experten wird empfohlen.

Efficacy and safety of fluoroquinolone-containing regimens in treating pulmonary Mycobacterium avium complex disease: A propensity score analysis

Background

Although combination therapy using clarithromycin, rifampicin, and ethambutol is recommended for patients with pulmonary Mycobacterium avium complex (MAC) disease, some patients do not tolerate it because of adverse effects or underlying diseases. The efficacy and safety of fluoroquinolone-containing combination regimens as an alternative remain uncertain. This study aimed to compare the efficacy and safety of fluoroquinolone-containing regimens with those of the standard regimens for treating pulmonary MAC disease.

Methods

We retrospectively included consecutive MAC patients who were treated in our hospital between January 2011 and May 2019. Patients treated with fluoroquinolone-containing regimens who had relapsed after treatment with standard regimens were excluded. A propensity score analysis was conducted to reduce selection bias, and the proportions of clinical improvement, defined by chest imaging findings and sputum conversion, were compared between the fluoroquinolone-containing regimen and standard regimen groups.

Results

We analyzed 28 patients who received fluoroquinolone-containing regimens and 46 who received the standard regimen. Fluoroquinolone-containing regimens were more likely selected for patients with cavitary lesions, diabetes mellitus, culture negativity, a low daily physical activity level, a decreased lymphocyte count and an increased CRP level. The propensity score was calculated using these variables (C-statistic of the area under the receiver operating characteristic curve of the propensity score: 0.807, p < 0.0001). The fluoroquinolone-containing regimens were significantly inferior to the standard regimen in clinical improvements (p = 0.002, Log-rank test) in the univariate analysis, but the significance was lost after adjusting for the propensity score (HR 0.553, 95% CI 0.285–1.074, p = 0.080). Six (21%) patients in the fluoroquinolone-containing regimen group and ten (22%) patients in the standard regimen group experienced low-grade adverse effects.

Conclusions

There was no significant difference in clinical improvement between these regimens after propensity score adjustment. A large-scale prospective study is required to validate these results.

Treatment of nontuberculous mycobacterial pulmonary disease: an official ATS/ERS/ESCMID/IDSA clinical practice guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

Antibiotic therapy success rate in pulmonary Mycobacterium avium complex: a systematic review and meta-analysis

Objectives: The incidence of Mycobacterium avium complex (MAC) pulmonary disease is increasing worldwide. We conducted a systematic review and meta-analysis to determine the treatment success rate of antibiotic therapy in MAC pulmonary disease and evaluate the effectiveness of aminoglycoside-containing regimens.Methods: We searched literature between 1 January 1980 to 19 June 2019. Studies with diagnosis criteria based on the current guidelines that reported treatment outcomes were included. We defined treatment success as the achievement of culture conversion and completion of the planned treatment without relapse while on treatment.Results: We retrieved 45 studies including 3862 patients. The estimated pooled treatment success rate was 68.1% [95% confidence interval (CI) 64.7-71.4%]. Based on the Cochrane tool, the included studies had a low risk of bias. Forty-two studies reported macrolide-containing regimens, while 6 studies included aminoglycoside-containing regimens. Macrolide-containing regimens led to better treatment success rates comparing to non-macrolide-containing regimens; 69% vs 58.5%, respectively. Treatment duration of 12 months or more showed better results.Conclusion: Poor treatment success rate of MAC pulmonary disease calls for more randomized clinical trials designed based on consensus definitions of the disease diagnosis and treatment. New drugs with a better adherence rate need to be developed.Systematic Review Registration: PROSPERO (pending registration ID: 151674).

Clinical characteristics and treatment outcomes of patients with macrolide-resistant Mycobacterium avium complex pulmonary disease: a systematic review and meta-analysis

Background

Macrolide is a key drug in the treatment of Mycobacterium avium complex pulmonary disease (MAC-PD). Macrolide-resistant MAC is gaining importance, but there are little data in clinical characteristics and treatment outcomes of macrolide-resistant MAC-PD (MR-MAC-PD).

Methods

We performed a systematic review and meta-analysis of published studies reporting clinical characteristics and treatment outcomes of patients with MR-MAC-PD. Risk of bias was assessed using the modified Newcastle-Ottawa Scale.

Results

Nine studies (seven retrospective and two prospective) comprising 319 patients were identified through a database search. Around 73% were women, and 52% had the fibrocavitary form. Pooled sputum culture conversion rate after combined multiple antibiotics or surgical resection was 21% (95% confidence interval [CI], 14–30%), and the one-year all-cause mortality was 10% (95% CI, 5–20%). There was no significant difference in treatment outcomes between nodular bronchiectatic and fibrocavitary types.

Conclusions

Even combination therapy with fluoroquinolone, aminoglycoside, and surgical resection, the treatment outcomes of MR-MAC-PD were poor. The investigation of new treatment modalities is urgent.

Serum oxidative stress in patients with pulmonary Mycobacterium avium complex disease

Background

The mechanism of progressive airway destruction in incurable chronic infection of the lung – termed pulmonary Mycobacterium avium complex (pMAC) disease – is currently unknown. The involvement of oxidative stress in a variety of progressive chronic respiratory diseases has been previously reported. It has been hypothesized that oxidative stress may be involved in the progression of airway destruction in pMAC disease.

Patients and methods

The study included 28 untreated patients with pMAC disease. The level of serum oxidative stress was quantitatively evaluated through the diacron reactive oxygen metabolites (d-ROMs) test, which indirectly measures the level of hydroperoxide in the serum. In addition, patients were divided into three groups based on the severity shown in the computed tomographic image.

Results

The level of serum oxidative stress exceeded the normal range (250–300 U.Carr [Carratelli Units]) in all patients with pMAC disease (mean: 495.5 ± 102.6 U.Carr; minimum–maximum: 340–734 U.Carr). The level of serum oxidative stress in patients with severe disease was significantly higher compared with that observed in patients with mild disease (434.6 ± 30.2 vs. 583.4 ± 95.1, respectively, p = 0.009).

Conclusions

In patients with pMAC disease, an elevation was observed in the level of serum oxidative stress. This increase in oxidative stress was more pronounced in patients with severe disease.

Development of Macrolide Resistance and Reinfection in Refractory Mycobacterium avium Complex Lung Disease

RATIONALE

Patients with refractory Mycobacterium avium complex lung disease (MAC-LD) undergo long-term macrolide therapy, but macrolide resistance develops infrequently.

OBJECTIVES

The aim of this study was to determine whether reinfection was a factor in the low incidence of macrolide resistance in patients with refractory MAC-LD.

METHODS

Among 481 patients with treatment-naive MAC-LD who started antibiotic treatment between January 2002 and December 2013, we identified 72 patients with refractory disease, characterized by persistently positive sputum cultures despite ≥12 months of treatment. Molecular analyses of the 23S ribosomal RNA gene responsible for macrolide resistance and serial mycobacterial genotyping were performed using stored MAC isolates.

MEASUREMENTS AND MAIN RESULTS

The median duration of treatment was 32 months (interquartile range, 24-41 mo) in 72 patients. After treatment for a median of 33 months (interquartile range, 21-44 mo), macrolide resistance developed in 16 (22%) patients. Molecular analysis of isolates from 15 patients revealed that 80% (12 of 15) had a point mutation at position 2,058 or 2,059 of the 23S ribosomal RNA gene. Of the 49 patients who had stored pre- and post-treatment isolates, mycobacterial genotyping revealed that reinfection by new MAC strains occurred in 36 (73%) patients. New MAC strains were found in 24 (49%) patients, and mixed infections with original and new strains occurred in 12 (24%) patients. Only 13 (27%) patients had persistent infections with their original MAC strains.

CONCLUSIONS

Refractory MAC-LD is commonly caused by reinfection with new strains rather than persistence of the original strain, which may explain the infrequent development of macrolide resistance in refractory MAC-LD. Clinical trial registered with www.clinicaltrials.gov (NCT00970801).

Auranofin Activity Exposes Thioredoxin Reductase as a Viable Drug Target in Mycobacterium abscessus

Nontuberculous mycobacteria (NTM) are highly drug-resistant, opportunistic pathogens that can cause pulmonary disease. The outcomes of the currently recommended treatment regimens are poor, especially for Mycobacterium abscessus New or repurposed drugs are direly needed. Auranofin, a gold-based antirheumatic agent, was investigated for Mycobacterium tuberculosis Here, we test auranofin against NTM in vitro and ex vivo We tested the susceptibility of 63 NTM isolates to auranofin using broth microdilution. Next, we assessed synergy between auranofin and antimycobacterial drugs using the checkerboard method and calculated the fractional inhibition concentration index (FICI). Using time-kill kinetics assays (TK), we assessed pharmacodynamics of auranofin alone and in combination with drug combinations showing the lowest FICIs for M. abscessus CIP 104536. A response surface analysis was used to assess synergistic interactions over time in TKs. Primary isolated macrophages were infected with M. abscessus and treated with auranofin. Finally, using KEGG Orthology, we looked for orthologues to auranofins drug target in M. tuberculosis M. abscessus had the lowest auranofin MIC₅₀ (2 μg/ml) among the tested NTM. The lowest average FICIs were observed between auranofin and amikacin (0.45) and linezolid (0.50). Auranofin exhibited concentration-dependent killing of M. abscessus, with >1-log killing at concentrations of >2× MIC. Only amikacin was synergistic with auranofin according to Bliss independence. Auranofin could not lower the intracellular bacterial load in macrophages. Auranofin itself may not be feasible for M. abscessus treatment, but these data point toward a promising, unutilized drug target.

In Vitro Activity of Bedaquiline and Delamanid against Nontuberculous Mycobacteria, Including Macrolide-Resistant Clinical Isolates

We evaluated the in vitro activities of the antimicrobial drugs bedaquiline and delamanid against the major pathogenic nontuberculous mycobacteria (NTM). Delamanid showed high MIC values for all NTM except Mycobacterium kansasii However, bedaquiline showed low MIC values for the major pathogenic NTM, including Mycobacterium avium complex, Mycobacterium abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. kansasii Bedaquiline also had low MIC values with macrolide-resistant NTM strains and warrants further investigation as a potential antibiotic for NTM treatment.

Managing antibiotic resistance in nontuberculous mycobacterial pulmonary disease: challenges and new approaches

Introduction: The incidence and prevalence rates of nontuberculous mycobacterial (NTM) pulmonary disease have been continuously increasing worldwide. However, the rate of successful treatment of this disease greatly needs improving, particularly when intrinsic (natural) drug resistance and acquired drug resistance in NTM pulmonary disease are associated with poor outcomes for patients. Areas covered: This review covers the major pathogens that cause NTM pulmonary disease caused by Mycobacterium avium complex, Mycobacterium abscessus, and Mycobacterium kansasii; the key drugs and recommended regimens used in the treatment of NTM pulmonary disease; the factors that contribute to resistance to the key drugs, including genetic factors and monotherapy; and the treatment strategies, including revised antibiotic regimens and surgery, that can be used to treat drug-resistant NTM pulmonary disease. Expert opinion: To avoid and overcome drug resistance in NTM pulmonary disease, the appropriate guideline-based treatments are essential, and clinical studies to evaluate new or repurposed drugs are urgently needed.

Multicentre, open label, randomised controlled trial comparing intermittent versus daily treatment for non-cavitary nodular/bronchiectatic Mycobacterium avium complex lung disease with rifampicin, ethambutol and clarithromycin (iREC): study protocol

Introduction

Standard treatment for nodular/bronchiectatic Mycobacterium avium complex lung disease (NB MAC-LD), excluding severe-status cases, differs between Japan and other countries. Internationally, three-drug combination intermittent treatment (three times a week administration) with macrolide, ethambutol and rifampicin is recommended, but a daily treatment regimen is recommended in Japan. To date, no randomised controlled study directly comparing intermittent treatment with daily treatment has been performed. The purpose of this study is to investigate the usefulness of intermittent treatment.

Methods and analysis

A total of 140 patients diagnosed with NB MAC-LD in Japan will be randomly assigned, in a 1:1 ratio, to intermittent treatment group or daily treatment group, and three-drug combination therapy with clarithromycin, rifampicin and ethambutol will be continued for 1 year. The primary endpoint is the proportion of patients requiring modification of the initial treatment regimen. Secondary endpoints are adverse events, sputum culture conversion, time to sputum culture conversion, improvement of chest CT findings, change in health-related quality of life score and development of clarithromycin resistance.

Ethics and dissemination

This trial was approved by the National Hospital Organisation Review Board for Clinical Trials (Headquarters). The results of this study will be reported at a society meeting or published in a peer-review journal.

Sitafloxacin-Containing Regimen for the Treatment of Refractory Mycobacterium avium Complex Lung Disease

Background

Sitafloxacin (STFX) exhibits potent activity against Mycobacterium avium complex (MAC) in both in vitro and in vivo experiments. However, limited data are available for the clinical efficacy and adverse effects of STFX and the susceptibility of refractory MAC lung disease (MAC-LD) to the drug. Therefore, this study was aimed at evaluating the clinical efficacy and safety of an STFX-containing regimen for the treatment of refractory MAC-LD.

Methods

We retrospectively evaluated treatment outcomes of 31 patients with refractory MAC-LD, who received an STFX-containing regimen for ≥4 weeks between January 2010 and July 2017. Refractory MAC-LD was defined as persistent positive sputum cultures for >6 months of macrolide-based standard therapy.

Results

Clarithromycin resistance (minimum inhibitory concentration [MIC] ≥32 μg/mL) was identified in 15 patients (48%). Twelve months after receiving the STFX-containing regimen, 26% and 19% of patients showed symptomatic and radiological responses, respectively. Although STFX-associated adverse effects were noted in 9 patients, their severity was grade 1 (National Cancer Institute Common Terminology Criteria); only 1 patient discontinued STFX because of suspected gastrointestinal disturbance. Negative sputum culture conversion was achieved in 7 patients (23%). Both univariate and multivariate logistic regression analyses revealed that surgery, low STFX MIC (≤1 μg/mL), and macrolide resistance were significant predictors of negative sputum culture conversion.

Conclusions

Our results demonstrate that STFX may be effective in one-fourth of patients with refractory MAC-LD. Prospective larger studies that include the analyses of MAC are needed to determine the clinical efficacy of STFX against refractory MAC-LD.

Multicenter evaluation of the biochip assay for rapid detection of mycobacterial isolates in smear-positive specimens

OBJECTIVES

The objective of this study was to conduct a multicentre evaluation of the performance of the biochip assay in the rapid identification of mycobacteria in smear-positive sputum specimens.

METHODS

A total of 1751 sputum specimens were obtained from 7 cities in Zhejiang, China. All of the specimens were used for the discrimination of Mycobacterium species using the biochip assay, and the results were compared to the golden standard method of culture, hsp65, 16S rRNA and rpoB sequence analysis.

RESULTS

In the 1751 sputum specimens, 1685 samples were cultured successfully; among these samples, 1361 were Mycobacterium tuberculosis, 323 were NTM and 1 was Nocadia farcinica. Of the 323 NTM, most of them were Mycobacterium intracellulare(52.5%) followed by Mycobacterium abscessus (20.7%), Mycobacterium avium (11.7%), Mycobacterium kansasii (9.6%) and Mycobacterium fortuitum (1.9%). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the biochip assay to differentiate TB and NTM from AFB positive specimens were 99.8%, 99.7%, 99.9%, 99.1%, 98.8%, 1, 1, and 99.7%, respectively. The concordance between the biochip assay and mycobacterial culture for the identification of NTM species was 95.4%.

CONCLUSIONS

The biochip assay is a reliable tool for the rapid identification of most mycobacteria in clinical sputum specimens. This assay can be helpful for physicians in the early diagnosis and treatment of mycobacterium infections.

Treatment of Mycobacterium avium Complex Pulmonary Disease

The pathogen Mycobacterium avium complex (MAC) is the most common cause of nontuberculous mycobacterial pulmonary disease worldwide. The decision to initiate long-term antibiotic treatment is difficult for the physician due to inconsistent disease progression and adverse effects associated with the antibiotic treatment. The prognostic factors for the progression of MAC pulmonary disease are low body mass index, poor nutritional status, presence of cavitary lesion(s), extensive disease, and a positive acid-fast bacilli smear. A regimen consisting of macrolides (clarithromycin or azithromycin) with rifampin and ethambutol has been recommended; this regimen significantly improves the treatment of MAC pulmonary disease and should be maintained for at least 12 months after negative sputum culture conversion. However, the rates of default and disease recurrence after treatment completion are still high. Moreover, treatment failure or macrolide resistance can occur, although in some refractory cases, surgical lung resection can improve treatment outcomes. However, surgical resection should be carefully performed in a well-equipped center and be based on a rigorous risk-benefit analysis in a multidisciplinary setting. New therapies, including clofazimine, inhaled amikacin, and bedaquiline, have shown promising results for the treatment of MAC pulmonary disease, especially in patients with treatment failure or macrolide-resistant MAC pulmonary disease. However, further evidence of the efficacy and safety of these new treatment regimens is needed. Also, a new consensus is needed for treatment outcome definitions as widespread use of these definitions could increase the quality of evidence for the treatment of MAC pulmonary disease.

Mutations in gyrA and gyrB in Moxifloxacin-Resistant Mycobacterium avium Complex and Mycobacterium abscessus Complex Clinical Isolates

Data on the frequency of gyrA and gyrB mutations in fluoroquinolone-resistant isolates of the Mycobacterium avium complex (MAC) and the Mycobacterium abscessus complex (MABC) are limited. In our analysis, we did not find any resistance-associated mutations in gyrA or gyrB in 105 MAC or MABC clinical isolates, including 72 moxifloxacin-resistant isolates. Our findings suggest that mechanisms other than gyrA and gyrB mutations contribute to moxifloxacin resistance in these organisms.

Adjuvant lung resection in the management of nontuberculous mycobacterial lung infection: A retrospective matched cohort study

BACKGROUND AND OBJECTIVES

Lung resection in patients with nontuberculous mycobacterial pulmonary disease (NTM-PD) is considered when medical therapy alone fails to provide long term control. Data regarding comparative and long-term outcomes are limited. We aimed to review indications and outcomes of adjuvant lung resection for NTM-PD compared with controls.

METHODS

We retrospectively studied 27 surgically treated patients, matched 1:1 for age, sex, NTM species, and radiologic pattern of disease, with control patients treated exclusively with antibiotics.

RESULTS

In the surgical group, the median (IQR) age was 55 (49-61) years and 74.1% were female. Eighteen patients had Mycobacterium avium complex, and 9 had M. xenopi. Operations included 8 pneumonectomies, 20 lobectomies, one segmentectomy and one lobectomy plus segmentectomy. Post-surgical complications occurred in 6 patients (20%), including 2 acute respiratory distress syndrome, 1 bronchopleural fistula, 1 pericardial tamponade, and 2 empyema. Complications were more common among patients operated upon for progressive disease despite medical therapy (OR 10, p = 0.025). Of 24 matched pairs followed for ≥1 year, sustained culture conversion was observed in 21 (87.5%) patients in the surgical group and in 11 (45.8%) patients in the non-surgical group (RR 2.36, 95%CI 1.37-4.03, p = 0.002). Median (IQR) percentage of follow-up time on antibiotics was 14% (0-100%) in the surgical group and 83% (10.8%-100%) in the non-surgical group (p = 0.195) during a median (IQR) follow-up of 16 (2-36) months.

CONCLUSIONS

NTM-PD patients who underwent adjuvant lung resection experienced significant morbidity and more frequently achieved sputum culture conversion. Long term antibiotic requirements may have been reduced.

Amikacin Inhalation as Salvage Therapy for Refractory Nontuberculous Mycobacterial Lung Disease

Although guidelines recommend amikacin (AMK) inhalation therapy for difficult-to-treat nontuberculous mycobacterial lung disease (NTM-LD), data are limited regarding the safety and clinical efficacy of this salvage therapy. We retrospectively evaluated the treatment outcomes of 77 patients with refractory NTM-LD caused by Mycobacterium abscessus complex (MABC) or M. avium complex (MAC) who initiated AMK inhalation therapy between February 2015 and June 2016. MABC was the most common etiology (n = 48, 62%), followed by MAC (n = 20, 26%) and mixed infections (n = 9, 12%). Isolates with macrolide resistance and baseline AMK resistance were identified in 63 (82%) patients and 5 (6%) patients, respectively. At 12 months after AMK inhalation therapy, 49% of patients had symptomatic improvement, whereas 42% had radiological improvement. Conversion to a negative sputum culture occurred in 14 (18%) patients, and the culture conversion rate was higher in patients infected with macrolide-susceptible isolates (7/14, 50%) than in those infected with macrolide-resistant isolates (7/63, 11%) (P = 0.003). Significant decreases in sputum semiquantitative culture positivity occurred after AMK inhalation therapy (P < 0.001). On multivariate analysis, conversion to a negative sputum culture was associated with mixed infections (P = 0.009), a forced expiratory volume in 1 s of greater than 60% (P = 0.008), and the absence of macrolide resistance (P = 0.003). Thirty-eight percent of patients experienced adverse effects, with ototoxicity (n = 15) being the most common. AMK inhalation salvage therapy may improve the treatment responses in some patients with refractory NTM-LD. However, considering the common adverse effects, further evaluation of the optimal dosage and intervals for AMK inhalation therapy is needed.

Linezolid as treatment for pulmonary Mycobacterium avium disease

Objectives

To identify the pharmacokinetic/pharmacodynamic parameters and exposures of linezolid in the treatment of pulmonary Mycobacterium avium complex (MAC) disease.

Methods

Human-derived monocytes infected with MAC were inoculated into hollow-fibre systems for dose-effect and dose-scheduling studies. We mimicked linezolid concentration-time profiles achieved in adult human lungs treated for 28 days. Sampling to confirm that the intended linezolid pharmacokinetics had been achieved, and for enumeration of MAC colony-forming units, was performed based on repetitive sampling from each system over the 28 days. We then performed 10 000 patient Monte Carlo simulations to identify doses associated with optimal effect in the clinic.

Results

Linezolid achieved a hitherto unprecedented feat of at least 1.0 log10 cfu/mL reduction. Efficacy was most closely linked to the AUC0-24/MIC ratio. The AUC0-24/MIC ratio associated with no change in bacterial burden or bacteriostasis was 7.82, while that associated with 1.0 log10 cfu/mL kill was 42.06. The clinical dose of 600 mg/day achieved or exceeded the bacteriostasis exposure in 98.73% of patients. The proportion of 10 000 patients treated with the standard 1200 mg/day who achieved the exposure for 1.0 log10 cfu/mL kill was 70.64%, but was 90% for 1800 mg/day. The proposed MIC breakpoint for linezolid is 16 mg/L, with which 49%-80% of clinical isolates would be considered resistant.

Conclusions

Linezolid is associated with a bactericidal effect in pulmonary MAC that is greater than that seen with other recommended drugs. However, because of the MIC distribution, doses that would optimize the bactericidal effect would be associated with a high adverse event rate.

A programme to create short-course chemotherapy for pulmonary Mycobacterium avium disease based on pharmacokinetics/pharmacodynamics and mathematical forecasting

Objectives

Pulmonary Mycobacterium avium complex (MAC) prevalence is on the rise worldwide. The average therapy duration is 1.5 years, which is associated with poor cure rates. Our objective was to develop a programme to design a combination therapy regimen for pulmonary MAC to be administered for 6 months or less with efficacy in > 90% of patients.

Methods

We performed a literature search for the following MeSH headings 'Mycobacterium avium' AND 'pharmacokinetics/pharmacodynamics' in PubMed up to 2016. The findings were then used to identify steps in the programme to design new regimens with faster microbial kill rates than the current standard regimen.

Results

First, we designed a strategy for rapid in vitro screening of all antibiotic classes for repurposing against pulmonary MAC. Secondly, we identified and compared maximal microbial kill rates (Emax), and optimal exposures of eight different antibiotics. These studies had all been performed in the hollow-fibre system model of pulmonary MAC (HFS-MAC). Thirdly, all drugs with a high Emax at clinically achievable optimal exposures will be chosen, and exposures associated with synergy or additivity for two/three drugs identified based on Bliss independence. Fourthly, the time-kill slopes and resistance suppression of the chosen combinations will be compared with those of standard combination therapy in the HFS-MAC. Finally, we will identify the clinical doses best able to achieve synergistic or additive combination exposures by taking into account pharmacokinetic variability.

Conclusions

Our stepwise pharmacokinetics/pharmacodynamics approach provides a scientific rationale and a strategy for achieving short-course chemotherapy for pulmonary MAC disease within a few years.

A 'shock and awe' thioridazine and moxifloxacin combination-based regimen for pulmonary Mycobacterium avium-intracellulare complex disease

Objectives

To develop a thioridazine/moxifloxacin-based combination regimen for treatment of pulmonary infection due to Mycobacterium avium-intracellulare complex (MAC) that kills bacteria faster than the standard treatment regimen.

Methods

Monocytes were infected with MAC and inoculated into the hollow-fibre system model for pulmonary MAC disease (HFS-MAC). We co-administered ethambutol plus azithromycin daily for 28 days, to achieve the same human concentration-time profiles that result from standard doses, in three HFS-MAC systems. Two experimental regimens consisted of thioridazine at an exposure associated with optimal kill, given intermittently on days 0, 3, 7 and 10. Regimen A consisted of thioridazine in combination with standard dose azithromycin for the entire study duration. Regimen B was thioridazine plus moxifloxacin at concentration-time profiles achieved by the standard daily dose administered for 14 days, followed by daily azithromycin. Each HFS-MAC was sampled for bacterial burden every 7 days.

Results

The bacteria in the non-treated HFS-MAC grew at a rate of 0.11 ± 0.01 log10 cfu/mL/day. The azithromycin/ethambutol regimen decreased bacterial burden by 1.21 ± 0.74 log10 cfu/mL below baseline during the first 7 days, after which it failed. Regimen A killed 3.28 ± 0.32 log10 cfu/mL below baseline up to day 14, after which regrowth occurred once thioridazine treatment stopped. Regimen B killed bacteria to below the limits of detection in 7 days (≥5.0 log10 cfu/mL kill), with rebound in the azithromycin continuation phase.

Conclusions

The thioridazine/moxifloxacin regimen demonstrated that rapid microbial kill could be achieved within 7 days. This is a proof of principle that short-course chemotherapy for pulmonary MAC is possible.

A novel ceftazidime/avibactam, rifabutin, tedizolid and moxifloxacin (CARTM) regimen for pulmonary Mycobacterium avium disease

Objectives

To compare the efficacy of ceftazidime/avibactam plus tedizolid-based combination regimens with the standard therapy of azithromycin, ethambutol and rifabutin for the treatment of pulmonary Mycobacterium avium complex (MAC) disease.

Methods

We mimicked the human pulmonary concentration-time profiles of ceftazidime/avibactam and tedizolid in combination, ceftazidime/avibactam, rifabutin, tedizolid and moxifloxacin (CARTM), and the standard regimen and examined microbial kill in triplicate hollow-fibre system model of intracellular pulmonary MAC (HFS-MAC) units. The tedizolid and moxifloxacin doses used were non-optimized; the tedizolid dose was that associated with bacteriostasis. Drugs were administered daily for 28 days. Each HFS-MAC was sampled in the central and peripheral compartment to ascertain that the intended drug exposures had been achieved. The peripheral compartments were sampled at regular intervals over the 28 days to quantify the burden of MAC.

Results

MAC-infected macrophages in the HFS-MAC achieved multi-fold higher intracellular versus extracellular concentrations of rifabutin, moxifloxacin, ceftazidime/avibactam. The non-optimized ceftazidime/avibactam plus tedizolid dual therapy held the bacterial burden at the same level as day 0 (stasis) throughout the 28 days. The standard therapy reduced the bacterial load 2 log10 cfu/mL below stasis on day 14 but started failing after that. The CARTM regimen achieved 3.2 log10 cfu/mL kill below stasis on day 21, but had started to fail by day 28.

Conclusions

The CARTM regimen promises to have kill rates better than standard therapy. Experiments to identify exposures of each of the four drugs associated with optimal effect in the CARTM combination are needed in order to design a short-course chemotherapy regimen.

Failure of the azithromycin and ethambutol combination regimen in the hollow-fibre system model of pulmonary Mycobacterium avium infection is due to acquired resistance

Objectives

To investigate the performance of the two backbone drugs in the standard combination therapy regimen in the hollow-fibre system (HFS) model of pulmonary Mycobacterium avium complex (MAC) infection.

Methods

Six HFS were inoculated with human-derived monocytes infected with MAC, and treated with 15 mg/kg of ethambutol and 500 mg of azithromycin daily for 28 days to recapitulate the concentration-time profiles seen in the lungs of humans treated with these drugs and doses. The concentration-time profiles achieved were validated by sampling the central compartment at seven timepoints over 24 h. The total MAC burden, as well as the subpopulation resistant to 3 × MIC of each drug, was identified based on sampling the peripheral compartment of each system on days 0, 3, 7, 14, 21 and 28 of therapy. The experiment was performed twice.

Results

In non-treated control HFS, MAC grew from 5.0 to 8.53 log10 cfu/mL in 28 days. The dual therapy killed a maximum of 1.52 ± 0.43 log10 cfu/mL during the first 7 days, after which it failed. By day 28 there was no difference in MAC burden between the combination-therapy-treated and non-treated systems. Failure arose in parallel with the emergence of acquired ethambutol resistance. By day 28, 100% of the bacterial population was ethambutol resistant in the combination-therapy-treated HFS replicates.

Conclusions

The backbone combination of macrolide and ethambutol has poor MAC kill rates and is ineffective. Microbial kill is rapidly abrogated by acquired drug resistance. This backbone should be replaced.