Outcomes of Intermittent Multidrug IV Therapy for Refractory Mycobacterium abscessus Pulmonary Disease

BACKGROUND

No studies have reported therapies for the treatment of patients with refractory Mycobacterium abscessus pulmonary disease (MAB-PD). We implemented intermittent multidrug IV therapy (IMIT) through repeated hospitalizations for patients with MAB-PD who were refractory to antibiotics for more than 12 months.

RESEARCH QUESTION

What are the effects of IMIT on patients with refractory MAB-PD?

STUDY DESIGN AND METHODS

The IV antibiotics administered for IMIT included amikacin, imipenem, and tigecycline, and the outcomes for 36 patients who underwent IMIT for refractory MAB-PD were evaluated. Patients were repeatedly hospitalized and administered IMIT on recurrent symptoms or radiographic evidence of deterioration, while maintaining oral/inhaled antibiotics.

RESULTS

Of the 36 patients, 26 (72%) had M abscessus subspecies abscessus (herein, M abscessus)-PD, and 10 (28%) had M abscessus subspecies massiliense (herein, M massiliense)-PD. The median number of hospitalizations for IMIT was two (interquartile range, 1-3) for patients with M abscessus-PD and one (interquartile range, 1-2) for patients with M massiliense-PD. At least one negative culture result and culture conversion were observed in 62% and 12% of patients with M abscessus-PD, and in 80% and 60% of patients with M massiliense-PD, respectively. Symptomatic improvement was observed in all patients, and radiologic improvement, including cavity amelioration or no deterioration, was observed in 42% and 70% of patients with M abscessus-PD and with M massiliense-PD, respectively. No resistance to clarithromycin or amikacin was acquired.

INTERPRETATION

IMIT with intermittent hospitalization can be a beneficial palliative treatment for patients with refractory MAB-PD. This therapy alleviated symptoms, slowed radiologic progression, and reduced the bacterial burden in some patients. However, radiologic and microbiological responses to IMIT were more apparent in M massiliense-PD than in M abscessus-PD.

Evolution of Mycobacterium abscessus in the human lung: Cumulative mutations and genomic rearrangement of porin genes in patient isolates

BACKGROUND

Mycobacterium abscessus subspecies massiliense (M. massiliense) is increasingly recognized as an emerging bacterial pathogen, particularly in cystic fibrosis (CF) patients and CF centres' respiratory outbreaks. We characterized genomic and phenotypic changes in 15 serial isolates from two CF patients (1S and 2B) with chronic pulmonary M. massiliense infection leading to death, as well as four isolates from a CF centre outbreak in which patient 2B was the index case.

RESULTS

Comparative genomic analysis revealed the mutations affecting growth rate, metabolism, transport, lipids (loss of glycopeptidolipids), antibiotic susceptibility (macrolides and aminoglycosides resistance), and virulence factors. Mutations in 23S rRNA, mmpL4, porin locus and tetR genes occurred in isolates from both CF patients. Interestingly, we identified two different spontaneous mutation events at the mycobacterial porin locus: a fusion of two tandem porin paralogs in patient 1S and a partial deletion of the first porin paralog in patient 2B. These genomic changes correlated with reduced porin protein expression, diminished 14C-glucose uptake, slower bacterial growth rates, and enhanced TNF-α induction in mycobacteria-infected THP-1 human cells. Porin gene complementation of porin mutants partly restored 14C-glucose uptake, growth rate and TNF-α levels to those of intact porin strains.

CONCLUSIONS

We hypothesize that specific mutations accumulated and maintained over time in M. massiliense, including mutations shared among transmissible strains, collectively lead to more virulent, host adapted lineages in CF patients and other susceptible hosts.

Identification of Mycobacterium abscessus Subspecies by MALDI-TOF Mass Spectrometry and Machine Learning

Mycobacterium abscessus is one of the most common and pathogenic nontuberculous mycobacteria (NTM) isolated in clinical laboratories. It consists of three subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. bolletii, and M. abscessus subsp. massiliense. Due to their different antibiotic susceptibility pattern, a rapid and accurate identification method is necessary for their differentiation. Although matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) has proven useful for NTM identification, the differentiation of M. abscessus subspecies is challenging. In this study, a collection of 325 clinical isolates of M. abscessus was used for MALDI-TOF MS analysis and for the development of machine learning predictive models based on MALDI-TOF MS protein spectra. Overall, using a random forest model with several confidence criteria (samples by triplicate and similarity values >60%), a total of 96.5% of isolates were correctly identified at the subspecies level. Moreover, an improved model with Spanish isolates was able to identify 88.9% of strains collected in other countries. In addition, differences in culture media, colony morphology, and geographic origin of the strains were evaluated, showing that the latter had an impact on the protein spectra. Finally, after studying all protein peaks previously reported for this species, two novel peaks with potential for subspecies differentiation were found. Therefore, machine learning methodology has proven to be a promising approach for rapid and accurate identification of subspecies of M. abscessus using MALDI-TOF MS.

Multidisciplinary Treatment of Persistent Nontuberculous Mycobacterial Spinal Hardware Infection with a Pedicled Superior Gluteal Artery Perforator Flap

Nontuberculous mycobacterial hardware infections are extremely challenging to treat. Multidisciplinary care involving removal of infected hardware, thorough debridement, and durable soft tissue coverage in conjunction with antibiotic therapy is essential for successful management. This case report presents a patient with chronic mycobacterial spinal hardware infection that underwent successful treatment with aggressive serial debridements and reconstruction with a large pedicled superior gluteal artery perforator flap coverage.

The Use of Comparative Genomic Analysis for the Development of Subspecies-Specific PCR Assays for Mycobacterium abscessus

Mycobacterium abscessus complex (MABC) is an important pathogen of immunocompromised patients. Accurate and rapid determination of MABC at the subspecies level is vital for optimal antibiotic therapy. Here we have used comparative genomics to design MABC subspecies-specific PCR assays. Analysis of single nucleotide polymorphisms and core genome multilocus sequence typing showed clustering of genomes into three distinct clusters representing the MABC subspecies M. abscessus, M. bolletii and M. massiliense. Pangenome analysis of 318 MABC genomes from the three subspecies allowed for the identification of 15 MABC subspecies-specific genes. In silico testing of primer sets against 1,663 publicly available MABC genomes and 66 other closely related Mycobacterium genomes showed that all assays had >97% sensitivity and >98% specificity. Subsequent experimental validation of two subspecies-specific genes each showed the PCR assays worked well in individual and multiplex format with no false-positivity with 5 other mycobacteria of clinical importance. In conclusion, we have developed a rapid, accurate, multiplex PCR-assay for discriminating MABC subspecies that could improve their detection, diagnosis and inform correct treatment choice.

Development of a nucleic acid chromatography assay for the detection of commonly isolated rapidly growing mycobacteria

Introduction. Non-tuberculosis mycobacterium infections are increasing worldwide, including those caused by rapidly growing mycobacteria (RGM).Gap Statement. The identification of the aetiological agent in the context of infections is essential for the adoption of an adequate therapeutic approach. However, the methods for the rapid distinction of different RGM species are less than optimal.Aim. To develop a nucleic acid chromatography kit to identify clinically common RGM.Methodology. We tried to develop a nucleic acid chromatography kit designed to detect four RGM species (including three subspecies) i.e. Mycobacterium abscessus subsp. abscessus, Mycobacterium abscessus subsp. bolletii (detected as M. abscessus/bolletii) Mycobacterium abscessus subsp. massiliense, Mycobacterium fortuitum, Mycobacterium chelonae and Mycobacterium peregrinum. The amplified target genes for each species/subspecies using multiplex PCR were analysed using a nucleic acid chromatography assay.Results. Among the 159 mycobacterial type strains and 70 RGM clinical isolates tested, the developed assay correctly identified all relevant RGM without any cross-reactivity or false-negatives. The limits of detection for each species were approximately 0.2 pg µl^-1.Conclusion. The rapid and simple nucleic acid chromatography method developed here, which does not involve heat denaturation, may contribute to the rapid identification and treatment of RGM infections.

Molecular epidemiology and phylogenomic analysis of Mycobacterium abscessus clinical isolates in an Asian population

Mycobacterium abscessus comprises three subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. bolletii, and M. abscessus subsp. massiliense. These closely related strains are typically multi-drug-resistant and can cause difficult-to-treat infections. Dominant clusters of isolates with increased pathogenic potential have been demonstrated in pulmonary infections in the global cystic fibrosis (CF) population. An investigation was performed on isolates cultured from an Asian, predominantly non-CF population to explore the phylogenomic relationships within our population and compare it to global M. abscessus isolates. Whole-genome-sequencing was performed on M. abscessus isolates between 2017 and 2019. Bioinformatic analysis was performed to determine multi-locus-sequence-type, to establish the phylogenetic relationships between isolates, and to identify virulence and resistance determinants in these isolates. A total of 210 isolates were included, of which 68.5 % (144/210) were respiratory samples. These isolates consisted of 140 (66.6 %) M. abscessus subsp. massiliense, 67 (31.9 %) M. abscessus subsp. abscessus, and three (1.4 %) M. abscessus subsp. bolletii. Dominant sequence-types in our population were similar to those of global CF isolates, but SNP differences in our population were comparatively wider despite the isolates being from the same geographical region. ESX (ESAT-6 secretory) cluster three appeared to occur most commonly in ST4 and ST6 M. abscessus subsp. massiliense, but other virulence factors did not demonstrate an association with isolate subspecies or sample source. We demonstrate that although similar predominant sequence-types are seen in our patient population, cross-transmission is absent. The risk of patient-to-patient transmission appears to be largely limited to the vulnerable CF population, indicating infection from environmental sources remains more common than human-to-human transmission. Resistance and virulence factors are largely consistent across the subspecies with the exception of clarithromycin susceptibility and ESX-3.

Radiographic severity and treatment outcome of Mycobacterium abscessus complex pulmonary disease

INTRODUCTION

The lack of reliable predictors for the treatment response complicates decisions to initiate treatment in patients with Mycobacterium abscessus complex pulmonary disease (MABC-PD). We aimed to investigate whether baseline radiographic disease severity is associated with treatment outcome in MABC-PD.

METHOD

We retrospectively analyzed 101 patients with MABC-PD (54 with M. abscessus-PD and 47 with M. massiliense-PD) treated in a tertiary referral hospital between January 2006 and December 2019. Using chest computed tomography images, baseline radiographic disease severity was quantitatively scored according to five categories of radiographic lesions (bronchiectasis, bronchiolitis, cavities, nodules, and consolidation).

RESULTS

Treatment success was achieved in 53.7% of patients with M. abscessus-PD and 85.1% of patients with M. massiliense-PD. Higher overall scores for baseline radiographic disease severity were associated with treatment failure in patients with M. massiliense-PD (aOR 1.35, 95% CI 1.02-1.79 for each 1-point increase in severity score), as well as in patients with M. abscessus-PD (aOR 1.15, 95% CI 1.00-1.33). This was particularly prominent in patients with overall severity score of ≥14 (aOR 31.16, 95% CI 1.12-868.95 for M. massiliense-PD and aOR 3.55, 95% CI 1.01-12.45 for M. abscessus-PD). Among variable radiographic abnormalities, the score for cavitary lesion severity was associated with treatment failure in patients with M. abscessus-PD (aOR 1.26, 95% CI 1.01-1.56), but not in patients with M. massiliense-PD.

CONCLUSIONS

Given the association between baseline radiographic disease severity and treatment outcome, initiating treatment should be actively considered before significant progression of radiographic lesions in patients with MABC-PD.

Treatment of Mycobacterium abscessus Pulmonary Disease

Mycobacterium abscessus is the second most common nontuberculous mycobacterial lung disease pathogen and comprises three subspecies: abscessus, massiliense, and bolletii. Subspecies identification is critical for disease management, as subspecies abscessus and bolletii have an inducible macrolide resistance gene [erm(41)] that results in clinical macrolide resistance. In contrast, subspecies massiliense does not have an active erm(41) gene and is therefore susceptible in vitro and clinically to macrolide-containing regimens. M abscessus is also vulnerable to acquired mutational macrolide resistance. Macrolide resistance has such a profoundly negative impact on M abscessus treatment response that preserving macrolide susceptibility with adequate companion drugs for macrolides is among the highest treatment priorities. After the macrolides, amikacin is regarded as the next most important drug for M abscessus treatment, although data validating that assertion are lacking. The considerations for preventing acquired macrolide resistance also apply to amikacin. Recent guidelines suggest that treatment should be guided by in vitro susceptibilities but, aside from macrolides and amikacin, no other antibiotics have a validated minimum inhibitory concentration for M abscessus. Currently, phase therapy (intensive and continuation) is recommended for M abscessus. This approach is successful with macrolide-susceptible M abscessus but not with macrolide-resistant M abscessus, in which even more aggressive therapy is not predictably successful. Newer drugs have become available, with encouraging in vitro activity against M abscessus, but in vivo validation of their superiority to current agents is not yet available. In the absence of unequivocally effective regimens, we offer suggestions for managing this treatment-refractory organism.

Outcomes of Inhaled Amikacin-Containing Multidrug Regimens for Mycobacterium abscessus Pulmonary Disease

BACKGROUND

Mycobacterium abscessus pulmonary disease (M abscessus-PD) is challenging to treat because of its resistance to antibiotics.

RESEARCH QUESTION

What are the outcomes of treatment-naive patients with M abscessus-PD treated with inhaled amikacin-containing multidrug regimens?

STUDY DESIGN AND METHODS

We identified 82 treatment-naive patients with M abscessus-PD from a prospective observational cohort treated with regimens containing inhaled amikacin with or without clofazimine between March 2015 and June 2018 (ClinicalTrials.gov identifier: NCT00970801). During the initial phase, all patients received IV amikacin, imipenem (or cefoxitin), and oral azithromycin. Oral clofazimine was added in cases of (1) M abscessus subspecies abscessus (here M abscessus) or (2) M abscessus subspecies massiliense (here M massiliense) with cavitary lesions. During the continuation phase, amikacin was changed from an injectional to inhalational form.

RESULTS

Of 82 patients, 46 (56%) had M massiliense-PD and 36 (44%) had M abscessus-PD. Among 59 patients with nodular bronchiectatic disease (72%), 23 of 59 had a concurrent cavitary lesion. The remaining 23 patients (28%) had fibrocavitary disease. Twelve months after treatment initiation, cure was achieved in 53 patients (65%): 42 of 46 patients (91%) with M massiliense-PD and 11 of 36 patients (31%) with M abscessus-PD (P < .001). Symptomatic and radiologic improvements were observed in 72 patients (88%) and 64 patients (78%), respectively, with significantly greater improvement in patients with M massiliense-PD (symptom improvement, 96% vs 78% [P = .047]; improvement on CT scanning, 93% vs 61% [P = .002]).

INTERPRETATION

Inhaled amikacin with or without clofazimine in the regimen provides favorable treatment outcomes in M massiliense-PD. However, more effective treatments are needed for M abscessus-PD.

Human Cytomegalovirus-Induced Interleukin-10 Production Promotes the Proliferation of Mycobacterium massiliense in Macrophages

Human cytomegalovirus (HCMV) exploits the interleukin-10 (IL-10) pathway as a part of its infection cycle through the manipulation of the host IL-10 signaling cascade. Based on its immunomodulatory nature, HCMV attenuates the host immune response and facilitates the progression of co-infection with other pathogens in an immune-competent host. To investigate the impact of HCMV infection on the burden of non-tuberculous mycobacteria (NTM), whose prevalence is growing rapidly worldwide, macrophages were infected with HCMV and further challenged with Mycobacterium massiliense in vitro. The results showed that HCMV infection significantly increased host IL-10 synthesis and promoted the proliferation of M. massiliense in an IL-10-dependent manner. Transcriptomic analysis revealed that HCMV infection dampened the regulatory pathways of interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin-1 (IL-1), consequently abrogating the immune responses to M. massiliense coinfection in macrophages. These findings provide a mechanistic basis of how HCMV infection may facilitate the development of pathogenic NTM co-infection by upregulating IL-10 expression.

Disseminated Mycobacterium massiliense infection in a patient with myelodysplastic syndrome undergoing allogeneic bone marrow transplantation

Nontuberculous mycobacteria are ubiquitous in water and soil, and the subset of rapidly growing mycobacteria species can cause severe infections in immunocompromised patients. Solid organ or hematopoietic stem cell transplantation (HSCT) recipients are known to be susceptible to infection by nontuberculous mycobacteria. The nontuberculous mycobacteria species Mycobacterium massiliense (M massiliense) has been classified as a rapidly growing mycobacteria and recognized as a pathogen causing lung and soft tissue infections in humans. However, there have been only a few reported cases of M massiliense infection after solid organ transplantation and HSCT. We herein report another case of M massiliense infection after allogeneic HSCT, which manifested as soft tissue infection, lung infection, and bacteremia.

Mycobacterium bolletii Lung Disease in Cystic Fibrosis

BACKGROUND

The cystic fibrosis (CF) pathogen, Mycobacterium abscessus complex, covers three subspecies: M. abscessus, M. massiliense, and M. bolletii. There are no clinical outcome data concerning M. bolletii. Our aim was to characterize M. bolletii lung infections in patients with CF.

METHODS

We included patients with M. bolletii lung infection recorded between 1994 and 2012 in France. Data were collected from the CF registry, medical records, and questionnaires submitted to the CF primary physician. Strains were typed by multilocus sequence typing analysis.

RESULTS

Fifteen cases were identified in nine CF centers. Nine patients (60%) presented with nontuberculous mycobacterial pulmonary disease. Follow-up of 13 patients showed a trend to more rapid decline in FEV₁ in the first year of colonization (-9.4%; SD 19.3) in comparison with noninfected control subjects (-2.3%; SD 12.1) (P = .16). Twelve patients were treated, and 11 received oral macrolides. Treatment-induced eradication occurred in five patients (41.7%). Four patients died (26.7%), including one patient with fatal nontuberculous mycobacterial pulmonary disease. Inducible macrolide resistance was demonstrated in all strains. Patients always harbored unique strains.

CONCLUSIONS

Our study reports the largest study cohort of CF patients infected with M. bolletii. M. bolletii infection affects both children and young adults, is most often symptomatic, and may be fatal. Macrolide-based therapies have poor effectiveness. There is no evidence of patient-to-patient transmission.

Development of a loop-mediated isothermal amplification coupled lateral flow dipstick targeting erm(41) for detection of Mycobacterium abscessus and Mycobacterium massiliense

Mycobacterium abscessus (M. abscessus) and Mycobacterium massiliense (M. massiliense) are major pathogens that cause post-surgical wound infection and chronic pulmonary disease. Although they are closely related subspecies of M. abscessus complex, their infections are associated with different drug-resistance and cure rate. In the present study, a loop-mediated isothermal amplification (LAMP) coupled with lateral flow dipstick (LFD) method was developed to simultaneous detect M. abscessus and M. massiliense, via specific erm(41) gene. The amplification was carried out at 65 °C for only 60 min, and the results could be visualized on a lateral flow strip. Positive results only occurred in M. abscessus and M. massiliense, no cross-reaction with other mycobacterial species was observed. Therefore, the cost-effective MABC (M. abscessus complex)–LAMP–LFD method developed here was able to correct the diagnose of M. abscessus and M. massiliense infection in a short time. Thus, this method could be used to guide clinicians in treatment of M. abscessus group infections.

Drug susceptibility patterns of Mycobacterium abscessus and Mycobacterium massiliense isolated from respiratory specimens

In this study, we aimed to retrospectively investigate and compare the drug susceptibility patterns of two major Mycobacterium abscessus complex (MABC) species; M. abscessus and M. massiliense. A total of 546 MABC respiratory isolates (277 M. abscessus and 269 M. massiliense) from 2011 to 2016 were analyzed in this study. We estimated minimum inhibitory concentrations (MICs) using the broth microdilution method, and we calculated MIC₅₀ and MIC₉₀ values from the MIC distribution. Both M. abscessus and M. massiliense were highly susceptible to amikacin and linezolid. For M. abscessus, the proportions of inducible and acquired resistance to clarithromycin were 68.6% and 12.3%, respectively. Only 15.2% of M. abscessus remained susceptible at day 14. On the other hand, none of the M. massiliense showed inducible resistance and 6.3% showed acquired resistance to clarithromycin. A total of 92.6% of the M. massiliense remained susceptible at day 14. The resistance rate of M. abscessus to moxifloxacin (90.3%) was significantly higher than that of M. massiliense (83.3%; p = 0.016). These susceptibility differences may explain the divergent treatment outcomes between patients with pulmonary disease caused by these two species.

Mycobacterium abscessus subspecies massiliense infection after skin graft and cholecystectomy in a burn patient

Diagnosing skin and soft tissue infections due to rapidly growing mycobacteria (RGM) can often prove difficult, leading to delays in treatment. Postoperative infections caused by RGM are increasingly recognized both within and outside the USA, but are rarely encountered in burn units. We report a case of postoperative skin and soft tissue infection along a cholecystectomy incision in a burn patient caused by Mycobacterium abscessus subsp. massiliense. Postoperative infections caused by RGM require a high index of suspicion, often necessitating biopsy for definitive diagnosis. Physicians should consider this diagnosis when postoperative infections arise later than typically seen for routine bacterial infections and fail to respond to first-line therapy.

In vitro activity of tedizolid against the Mycobacterium abscessus complex

Infections due to Mycobacterium abscessus carry a poor prognosis since this rapidly growing mycobacterium is intrinsically resistant to most antibiotics. Here, we evaluate the in vitro activity of the new oxazolidinone tedizolid against a collection of 44M. abscessus clinical isolates. The MIC₅₀s and MIC₉₀s of tedizolid (2 and 8μg/mL, respectively) were 2- to 16-fold lower than those of linezolid. There was no difference between the 3M. abscessus subspecies. Time-kill assays did not show any bactericidal activity at 4- and 8-fold the MIC. Combination of tedizolid with clarithromycin was synergistic against 1 out of 6 isolates, while indifferent interactions were observed for tedizolid combined with tigecycline, ciprofloxacin, and amikacin.

Mycobacteriological characteristics and treatment outcomes in extrapulmonary Mycobacterium abscessus complex infections

OBJECTIVES

The differentiation between Mycobacterium abscessus subspecies abscessus (M. abscessus) and Mycobacterium abscessus subspecies massiliense (M. massiliense) and determination of the presence of inducible resistance to macrolide antibiotics are important factors in the management of patients with Mycobacterium abscessus complex (MABC) infections. Unlike pulmonary MABC infections, little information on extrapulmonary MABC infections is available.

METHODS

The molecular identification of clinical isolates was performed, and the clinical characteristics and treatment outcomes of 20 consecutive patients with extrapulmonary MABC infections were assessed.

RESULTS

M. abscessus and M. massiliense each caused 10 (50%) of the cases. Eight (80%) M. abscessus isolates that had inducible resistance to clarithromycin harbored an intact erm(41) gene of the T28 variant, whereas two (20%) M. abscessus isolates had the C28 erm(41) variant and were susceptible to clarithromycin. All M. massiliense isolates had a truncated erm(41) gene and were susceptible to clarithromycin. The drug susceptibility profiles other than clarithromycin were similar for the M. abscessus and M. massiliense isolates. Of the 20 patients, 17 (85%) showed a favorable outcome, including all patients with M. massiliense infection and 70% (7/10) of patients with M. abscessus infection. Favorable outcomes were associated with M. massiliense and M. abscessus isolates with a non-functional erm(41) gene (p=0.049).

CONCLUSIONS

Precise species and subspecies identification and the determination of macrolide susceptibility are recommended for the optimal treatment of extrapulmonary MABC infections.

In vitro activity of clarithromycin in combination with other antimicrobial agents against Mycobacterium abscessus and Mycobacterium massiliense

Macrolides, especially clarithromycin (CLA), remain the cornerstone of therapy for Mycobacterium abscessus complex infections. The purpose of this study was to gather results from in vitro drug susceptibility testing of M. abscessus and Mycobacterium massiliense for the combination of CLA with various other agents, including linezolid (LZD), moxifloxacin (MOX), amikacin (AMK) and tigecycline (TGC). A total of 40 M. abscessus complex isolates were studied, comprising 20 M. abscessus and 20 M. massiliense strains. In vitro drug susceptibility testing revealed that the percentage of TGC-resistant isolates among M. massiliense was significantly lower than that among M. abscessus (P = 0.047). In addition, 17 (85.0%) of 20 M. massiliense isolates showed a synergistic effect for the CLA + MOX combination, which was significantly higher than for M. abscessus (1/20; 5.0%) (P <0.001). Similarly, synergy for the CLA + TGC combination was found in 5 (25.0%) M. abscessus isolates and 13 (65.0%) M. massiliense isolates, with a significant difference between the two subspecies (P = 0.038). For CLA + LZD and CLA + AMK combinations, statistical analysis demonstrated that there was no significant difference in the proportion of synergistic effect between the two subspecies (P > 0.05). In conclusion, these data demonstrate that M. abscessus and M. massiliense exhibit significant differences in TGC susceptibility. In addition, the activity of CLA in combination with MOX or TGC showed better synergistic activity against M. massiliense than against M. abscessus.

Clinical Characteristics and Treatment Outcomes of Patients with Macrolide-Resistant Mycobacterium massiliense Lung Disease

Macrolide antibiotics are cornerstones in the treatment of Mycobacterium massiliense lung disease. Despite the emergence of resistance, limited data on macrolide-resistant M massiliense lung disease are available. This study evaluated the clinical features and treatment outcomes of patients and the molecular characteristics of macrolide-resistant M massiliense isolates. We performed a retrospective review of medical records and genetic analyses of clinical isolates from 15 patients who had macrolide-resistant M massiliense lung disease between September 2005 and February 2015. Nine patients (60%) had the nodular bronchiectatic form of the disease, and six (40%) had the fibrocavitary form. Before the detection of macrolide resistance, three patients (20%) were treated with macrolide monotherapy, four (27%) with therapy for presumed Mycobacterium avium complex infections, and eight (53%) with combination antibiotic therapy for M massiliense lung disease. The median treatment duration after the detection of resistance was 18.7 months (interquartile range, 11.2 to 39.8 months). Treatment outcomes were poor, with a favorable outcome being achieved for only one patient (7%), who underwent surgery in addition to antibiotic therapy. The 1-, 3-, and 5-year mortality rates were 7, 13, and 33%, respectively. Of the 15 clinical isolates, 14 (93%) had point mutations at position 2058 (n = 9) or 2059 (n = 5) of the 23S rRNA gene, resulting in macrolide resistance. Our study indicates that treatment outcomes are poor and mortality rates are high after the development of macrolide resistance in patients with M massiliense lung disease. Thus, preventing the development of macrolide resistance should be a key consideration during treatment.

Progression and Treatment Outcomes of Lung Disease Caused by Mycobacterium abscessus and Mycobacterium massiliense

BACKGROUND

Mycobacterium abscessus and Mycobacterium massiliense are grouped as the Mycobacterium abscessus complex. The aim of this study was to elucidate the differences between M. abscessus and M. massiliense lung diseases in terms of progression rate, treatment outcome, and the predictors thereof.

METHODS

Between 1 January 2006 and 30 June 2015, 56 patients and 54 patients were diagnosed with M. abscessus and M. massiliense lung diseases, respectively. The time to progression requiring treatment and treatment outcomes were compared between the 2 groups of patients, and predictors of progression and sustained culture conversion with treatment were analyzed. In addition, mediation analysis was performed to evaluate the effect of susceptibility to clarithromycin on treatment outcomes.

RESULTS

During follow-up, 21 of 56 patients with M. abscessus lung diseases and 21 of 54 patients with M. massiliense lung diseases progressed, requiring treatment. No difference was detected in the time to progression between the 2 patient groups. Lower body mass index, bilateral lung involvement, and fibrocavitary-type disease were identified as predictors of disease progression. Among the patients who began treatment, infection with M. massiliense rather than M. abscessus and the use of azithromycin rather than clarithromycin were associated with sustained culture conversion. The difference in treatment outcomes was partly mediated by the organism's susceptibility to clarithromycin.

CONCLUSIONS

Progression rates were similar but treatment outcomes differed significantly between patients with lung disease caused by M. abscessus and M. massiliense. This difference in treatment outcomes was partly explained by the susceptibility of these organisms to clarithromycin.

Clinical features and treatment outcomes of septic arthritis due to Mycobacterium massiliense associated with intra-articular injection: a case report

Background

There are increasing reports on nosocomial Mycobacterium massiliense infection, but septic arthritis and osteomyelitis because of that microorganism is rare. This report focuses on the clinical aspects of M. massiliense arthritis outbreak concurrent with soft tissue infection.

Case presentation

An outbreak of septic arthritis among patients who had been injected at a single clinic occurred in South Korea between April and September 2012. This may be associated with repeated injection of triamcinolone contaminated with M. massiliense. Nine of the Korean patients visited our hospital complaining of painful swelling of the knees. During treatment course, patients are suffered from soft tissue abscess around the injection site. Acid-fast bacilli culture for infected tissue was positive in five patients, and polymerase chain reaction for non-tuberculous mycobacteria was positive in four patients. They were treated with antibiotics, repeated arthroscopic surgeries, incision and drainage for a long time. All patients were eventually cured but three patients have suffered from a decreased range of motion.

Conclusion

Early clinical suspicion and microbiological diagnosis are key factors in reducing morbidity since septic arthritis with M. massiliense manifests late after the injection and treatment of it is a laborious process.

An in vitro model of granuloma-like cell aggregates substantiates early host immune responses against Mycobacterium massiliense infection

Mycobacterium massiliense (M. mass), belonging to the M. abscessus complex, is a rapidly growing mycobacterium that is known to cause tuberculous-like lesions in humans. To better understand the interaction between host cells and M. mass, we used a recently developed in vitro model of early granuloma-like cell aggregates composed of human peripheral blood mononuclear cells (PBMCs). PBMCs formed granuloma-like, small and rounded cell aggregates when infected by live M. mass. Microscopic examination showed monocytes and macrophages surrounded by lymphocytes, which resembled cell aggregation induced by M. tuberculosis (M. tb). M. mass-infected PBMCs exhibited higher expression levels of HLA-DR, CD86 and CD80 on macrophages, and a significant decrease in the populations of CD4+ and CD8+ T cells. Interestingly, low doses of M. mass were sufficient to infect PBMCs, while active host cell death was gradually induced with highly increased bacterial loads, reflecting host destruction and dissemination of virulent rapid-growing mycobacteria (RGM). Collectively, this in vitro model of M. mass infection improves our understanding of the interplay of host immune cells with mycobacteria, and may be useful for developing therapeutics to control bacterial pathogenesis.

Summary: An in vitro model of granuloma-like cell aggregates infected with Mycobacterium massiliense improves our understanding of the interplay of host immune cells with mycobacteria.

Biochemical Characterization of β-Lactamases from Mycobacterium abscessus Complex and Genetic Environment of the β-Lactamase-Encoding Gene

The objectives of this study were to determine the kinetic parameters of purified recombinant Bla_Mab and Bla_Mmas by spectrophotometry, analyze the genetic environment of the bla_Mab and bla_Mmas genes in both species by polymerase chain reaction and sequencing, furthermore, in silico models of both enzymes in complex with imipenem were obtained by modeling tools. Our results showed that Bla_Mab and Bla_Mmas have a similar hydrolysis behavior, displaying high catalytic efficiencies toward penams, cephalothin, and nitrocefin; none of the enzymes are well inhibited by clavulanate. Bla_Mmas hydrolyzes imipenem at higher efficiency than cefotaxime and aztreonam. Bla_Mab and Bla_Mmas showed that their closest structural homologs are KPC-2 and SFC-1, which correlate to the mild carbapenemase activity toward imipenem observed at least for BlaMmas. They also seem to differ from other class A β-lactamases by the presence of a more flexible Ω loop, which could impact in the hydrolysis efficiency against some antibiotics. A -35 consensus sequence (TCGACA) and embedded at the 3' end of MAB_2874, which may constitute the bla_Mab and bla_Mmas promoter. Our results suggest that the resistance mechanisms in fast-growing mycobacteria could be probably evolving toward the production of β-lactamases that have improved catalytic efficiencies against some of the drugs commonly used for the treatment of mycobacterial infections, endangering the use of important drugs like the carbapenems.

Mycobacterium abscessus Complex Infections in Humans

New treatments, rapid and inexpensive identification methods, and measures to contain nosocomial transmission and outbreaks are urgently needed.

Mycobacterium abscessus complex comprises a group of rapidly growing, multidrug-resistant, nontuberculous mycobacteria that are responsible for a wide spectrum of skin and soft tissue diseases, central nervous system infections, bacteremia, and ocular and other infections. M. abscessus complex is differentiated into 3 subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. abscessus subsp. bolletii. The 2 major subspecies, M. abscessus subsp. abscessus and M.abscessus subsp. massiliense, have different erm(41) gene patterns. This gene provides intrinsic resistance to macrolides, so the different patterns lead to different treatment outcomes. M. abscessus complex outbreaks associated with cosmetic procedures and nosocomial transmissions are not uncommon. Clarithromycin, amikacin, and cefoxitin are the current antimicrobial drugs of choice for treatment. However, new treatment regimens are urgently needed, as are rapid and inexpensive identification methods and measures to contain nosocomial transmission and outbreaks.

Oral Macrolide Therapy Following Short-term Combination Antibiotic Treatment of Mycobacterium massiliense Lung Disease

BACKGROUND

Although Mycobacterium massiliense lung disease is increasing in patients with cystic fibrosis and non-cystic fibrosis bronchiectasis, optimal treatment regimens remain largely unknown. This study aimed to evaluate the efficacy of oral macrolide therapy after an initial 2-week course of combination antibiotics for the treatment of M massiliense lung disease.

METHODS

Seventy-one patients received oral macrolides, along with an initial 4-week (n = 28) or 2-week (n = 43) IV amikacin and cefoxitin (or imipenem) treatment. These patients were treated for 24 months (4-week IV group) or for at least 12 months after negative sputum culture conversion (2-week IV group).

RESULTS

Total treatment duration was longer in the 4-week IV group (median, 23.9 months) than in the 2-week IV group (15.2 months; P < .001). The response rates after 12 months of treatment were 89% for symptoms, 79% for CT scanning, and 100% for negative sputum culture results in the 4-week IV group. In the 2-week IV group, these values were 100% (P = .057), 91% (P = .177), and 91% (P = .147), respectively. Acquired macrolide resistance developed in two patients in the 2-week IV group. Genotyping analyses of isolates from patients who did not achieve negative sputum culture conversion during treatment and from those with positive culture results after successful treatment completion revealed that most episodes were due to reinfection with different genotypes of M massiliense.

CONCLUSIONS

Oral macrolide therapy after an initial 2-week course of combination antibiotics might be effective in most patients with M massiliense lung disease.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00970801; URL: www.clinicaltrials.gov.

Prolonged postprocedural outbreak of Mycobacterium massiliense infections associated with ultrasound transmission gel

Postprocedural infections by Mycobacterium abscessus complex are increasing worldwide, and the source and route of transmission are infrequently identified. Here the extension of a previous clustering of paediatric patients with surgical site infections due to a single strain of the subspecies M. massiliense is reported. The investigation was conducted at a 2200-bed teaching hospital in Taiwan and included microbial surveillance of the environment (water, air, equipment and supplies) and a case-control study. We performed molecular identification and typing of the isolates by a trilocus sequencing scheme, confirmed by multilocus sequencing typing and pulsed-field gel electrophoresis. We investigated 40 patients who developed postprocedure soft tissue or bloodstream infections by M. massiliense (TPE101) during a 3-year period. Thirty-eight patients were identified at hospital A, and one newborn and her mother were identified at hospital B (185 km from hospital A). A case-control study identified the association of invasive procedures (adjusted odds ratio, 9.13) and ultrasonography (adjusted odds ratio, 2.97) (both p <0.05) with acquiring the outbreak strain. Isolates from the cases and unopened bottles of ultrasound transmission gel were all of strain ST48 and indistinguishable or closely related by pulsed-field gel electrophoresis. After replacement of contaminated gel, no new cases were detected during 18 months' follow-up. This investigation identified the use of contaminated gel as the common source causing an outbreak on a larger scale than had been recognized. Our findings halted production by the manufacturer and prompted revision of hospital guidelines.

A cluster of Mycobacterium massiliense keratitis in foundry workers

Three consecutive workers from the same foundry had Mycobacterium massiliense keratitis. The strains isolated from each patient were identical. This is the first report of a non-surgery-related outbreak of non-tuberculous mycobacterial ocular infection. An investigation revealed that injured cornea with exposure to aerosolized non-tuberculous mycobacteria might account for this outbreak.

Mycobacterium abscessus. "Pleased to meet you, hope you guess my name..."

Mycobacterium abscessus is a formidable and difficult-to-treat mycobacterial pathogen with multiple drug-resistance mechanisms. The most important of these mechanisms is the presence of an inducible erythromycin methylase (erm) gene, because it confers macrolide resistance. It has recently been found that "M. abscessus" can be split into three species or subspecies based on gene sequence analysis other than the 16S rRNA gene and the presence or absence of a functional erm(41) gene. Several names have been applied to these three organisms, including M. abscessus or M. abscessus subsp. abscessus, Mycobacterium massiliense or M. abscessus subsp. massiliense, and Mycobacterium bolletii or M. abscessus subsp. bolletii. No universally accepted or recognized species or subspecies designations have emerged, and no names have been universally adopted for these organisms. This uncertainty has led to inconsistencies in the medical literature and understandable confusion by clinicians about the appropriate labels for "M. abscessus" isolates. We discuss the complexities involved in mycobacterial species/subspecies identification and taxonomy and suggest possible ways to improve the present state of uncertainty surrounding the labels for "M. abscessus" clinical isolates. We also suggest necessary changes in mycobacterial laboratory processing and reporting procedures for mycobacterial isolates.

Mycobacterium abscessus Complex Infections in Humans

Mycobacterium abscessus complex comprises a group of rapidly growing, multidrug-resistant, nontuberculous mycobacteria that are responsible for a wide spectrum of skin and soft tissue diseases, central nervous system infections, bacteremia, and ocular and other infections. M. abscessus complex is differentiated into 3 subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. abscessus subsp. bolletii. The 2 major subspecies, M. abscessus subsp. abscessus and M. abscessus subsp. massiliense, have different erm(41) gene patterns. This gene provides intrinsic resistance to macrolides, so the different patterns lead to different treatment outcomes. M. abscessus complex outbreaks associated with cosmetic procedures and nosocomial transmissions are not uncommon. Clarithromycin, amikacin, and cefoxitin are the current antimicrobial drugs of choice for treatment. However, new treatment regimens are urgently needed, as are rapid and inexpensive identification methods and measures to contain nosocomial transmission and outbreaks.

Mycobacterium massiliense Type II genotype leads to higher level of colony forming units and TNF-α secretion from human monocytes than Type I genotype

Recently, we introduced a novel Mycobacterium massiliense Type II genotype from Korean patients, in which all isolates showed only a rough (R) colony morphotype. In this study, we sought to compare clinical factors and virulence potentials of two genotypes of M. massiliense, Type I and Type II. Patients infected with Type II tend to be younger at infection than those infected with Type I (56.7 vs 62.3, p = 0.051). Type II was more significantly related to R colony type than Type I (34.1% vs 94.1%, p < 0.001). The Type II strain showed significantly more colony forming units (CFUs) and higher levels of TNF-α secretion in infection of human monocytes than the Type I strain. The challenge of extracted glycopeptidolipid (GPL) into human monocytes indicated that the loss of GPL from the cell wall of the Type II genotype led to a higher level of TNF-α secretion in a toll-like receptor 2(TLR2)-dependent manner. Taken together, our data suggest that the M. massiliense Type II genotype shows higher virulence than Type I, which may be due to the induction of TNF-α via the loss of GPL from the Type II cell wall.

Isolation of Mycobacterium massiliense from a corneal biopsy in India

Introduction:

Rapidly growing mycobacteria (RGM) are ubiquitous and are usually considered as saprophytes, and have been recovered from the environment, particularly in dust, watery soil and water distribution systems. However, Mycobacterium massiliense is a rare causative agent of ocular infection.

Case presentation:

We report a case of M. massiliense in a 44-year-old female with signs and symptoms of a corneal ulcer. We carried out PCR-based DNA sequencing targeting the hsp 65 gene for the identification of M. massiliense. To confirm the identification, we also performed PCR-based RFLP targeting the hsp65 gene and PCR-based DNA sequencing targeting the internal transcribed spacer region, which showed 97 % nucleotide identity with M. massiliense.

Conclusion:

To the best of our knowledge, this is the first study in India to report the detection of M. massiliense from a corneal biopsy.

The treatment of rapidly growing mycobacterial infections

Rapidly growing mycobacteria (RGM) include a diverse group of species. We address the treatment of the most commonly isolated RGM-M abscessus complex, M fortuitum, and M chelonae. The M abscessus complex is composed of 3 closely related species: M abscessus senso stricto (hereafter M abscessus), M massiliense, and M bolletii. Most studies address treatment of M abscessus complex, which accounts for 80% of lung disease caused by RGM and is the second most common RGM to cause extrapulmonary disease (after M fortuitum). The M abscessus complex represent the most drug-resistant nontuberculous mycobacteria and are the most difficult to treat.

A shorter treatment duration may be sufficient for patients with Mycobacterium massiliense lung disease than with Mycobacterium abscessus lung disease

BACKGROUND

Mycobacterium abscessus complex is the second most common organism isolated from patients with nontuberculous mycobacterial (NTM) lung disease in South Korea. This study aimed to compare clinical features and treatment outcomes of M. abscessus and Mycobacterium massiliense lung disease.

METHODS

We retrospectively identified stored clinical isolates of M. abscessus complex as either M. abscessus or M. massiliense and reviewed medical records to compare clinical characteristics and treatment responses. All patients were treated empirically over several months with multidrug regimens, including a macrolide and one or more parenteral agents.

RESULTS

Of the 249 patient isolates tested, 128 (59 with M. abscessus and 69 with M. massiliense) met the American Thoracic Society diagnostic criteria for NTM pulmonary disease, and treatment outcomes were analyzed in 48 patients (26 with M. abscessus and 22 with M. massiliense). The clinical and radiologic findings were similar between the two groups. Although the durations of parenteral and total treatment were significantly shorter in patients with M. massiliense than in those with M. abscessus (4.7 months vs 7.4 months, P = .006, and 12.1 months vs 16.3 months, P = .043), the treatment success rate was significantly higher in patients with M. massiliense (95.5%) than in M. abscessus cases (42.3%, P < .001).

CONCLUSION

Patients with M. massiliense pulmonary infection responded better to this antibiotic strategy than those with M. abscessus infection. A shortened duration of treatment may be sufficient for M. massiliense pulmonary infection.

Cutaneous Mycobacterium massiliense Infection of the Sole of the Feet

Mycobacterium massiliense which is recognized as a separate species from M. abscessus is little known regarding its clinical patterns and the response to treatment. We present a case of a localized cutaneous infection due to M. massiliense of the sole associated with acupuncture. M. massiliense was identified via polymerase chain reaction-hybridization analysis. We treated the patient with single-drug therapy consisting of clarithromycin for 4 months and the patient showed a significant response to this treatment.

Extrapulmonary infections caused by a dominant strain of Mycobacterium massiliense (Mycobacterium abscessus subspecies bolletii)

A single strain of Mycobacterium massiliense (BRA 100), a subspecies of the Mycobacterium abscessus complex, has been responsible for an epidemic of post-surgical infections in Brazil. Outside Brazil, this is the first report to describe a single emerging strain of M. massiliense (TPE 101) associated with extrapulmonary infections. This phenomenon may be underestimated because sophisticated molecular typing of M. abscessus is not routinely performed. Our molecular epidemiology study was triggered by an outbreak investigation. Nine case isolates were grown from the surgical sites of nine mostly paediatric patients receiving operations from 2010 to 2011. All available non-duplicated isolates of M. abscessus during this period were obtained for comparison. Mycobacteria were characterized by multilocus sequence analysis (MLSA), repetitive sequence PCR (rep-PCR) and pulsed-field gel electrophoresis (PFGE). Of 58 isolates of M. abscessus overall, 56 were clinical isolates. MLSA identified 36 of the isolates as M. massiliense. All case isolates were indistinguishable by PFGE and named the TPE 101 pulsotype. Of the stored strains of M. abscessus, TPE 101 strains were over-represented among the control surgical wound (7/7, 100%) and subcutaneous tissue isolates (4/5, 80%) but rare among the respiratory isolates (1/16, 6%) and absent from external skin, ocular and environmental samples. In conclusion, a unique strain of M. massiliense has emerged as a distinctive pathogen causing soft tissue infections in Taiwan. Further study to identify whether this is due to an occult common source or to specific virulence factors dictating tissue tropism is warranted.

Mycobacterial genotypes are associated with clinical manifestation and progression of lung disease caused by Mycobacterium abscessus and Mycobacterium massiliense

BACKGROUND

Mycobacterium abscessus and Mycobacterium massiliense, which cause lung disease, are variable in their clinical manifestation and progression. We hypothesized that mycobacterial genotypes represent their pathogenic phenotypes, which would result in particular genotypes being associated with disease progression.

METHODS

Variable number tandem repeat (VNTR) loci were selected to establish a genotype assay that was capable of differentiating patients with heterogeneous prognoses in the development cohort (48 isolates). The analysis was reevaluated in the validation cohort (63 isolates).

RESULTS

A total of 53 M. abscessus and 58 M. massiliense isolates were assembled into 3 clusters based on their VNTR genotyping. The patients in cluster A were more likely to have stable disease of the nodular bronchiectatic form; 100% of M. abscessus patients and 96% of M. massiliense patients were followed without antibiotic treatment for >24 months after diagnosis. In contrast, the patients in cluster B were more likely to have progressive disease of the nodular bronchiectatic form; 96% of M. abscessus patients and 81% of M. massiliense patients started antibiotic treatment within 24 months after diagnosis. All patients in cluster C had fibrocavitary disease and started antibiotic treatment immediately after diagnosis. The genetic distance of each clinical isolate from the reference strain was associated with the highest likelihood of disease progression and a disease phenotype of the fibrocavitary form (P < .001).

CONCLUSIONS

Mycobacterial genotyping of M. abscessus and M. massiliense may provide valuable information for predicting disease phenotype and progression.

Inhaled therapies, azithromycin and Mycobacterium abscessus in cystic fibrosis patients

Cystic fibrosis (CF) patients are at particularly high risk of developing lung disease caused by Mycobacterium abscessus complex (MABSC). Over the last 10 years, changes in CF treatment, with increasing use of inhaled therapies and low-dose azithromycin, have been accompanied by an increase in the prevalence of MABSC infections in CF patients. There is therefore some concern about the role of new CF treatments in the emergence of MABSC infections. We addressed this issue by means of a case-control study including 30 MABSC-positive cases and 60 nontuberculous mycobacteria-negative CF controls matched for age, sex and centre. We also compared practices at the CF centres with the highest prevalence of MABSC with those at the other centres. No positive association was found between MABSC lung disease and the use of inhaled therapies or low-dose azithromycin in the 4 years preceding MABSC isolation. These treatments were not significantly more frequently used at the CF centres with the highest MABSC prevalence rates. In conclusion, there is no evidence for a link between M. abscessus complex lung disease and inhaled therapies or low-dose azithromycin in patients with CF.

Identification of Cutaneous Mycobacterium massiliense Infections Associated with Repeated Surgical Procedures

Mycobacterium massiliense, an emerging pathogen that is increasingly reported as a causative agent in infections occurring during medical procedures, is difficult to be identified using conventional methods. Here we report the case of a cutaneous M. massiliense infection that was associated with repeated surgical procedures and that was identified via a comparative sequence analysis of rpoB and hsp65. The patient showed a substantial response to treatment with a combination of antimicrobial therapies consisting of clarithromycin, amikacin, and cefoxitin for 6 months.