The therapeutic approach to non-tuberculous mycobacterial infection of the lung

Tolerability Outcomes of American Thoracic Society/Infectious Diseases Society of America Guideline-Recommended Multidrug Antibiotic Treatment for Mycobacterium avium Complex Pulmonary Disease in US Medicare Beneficiaries With Bronchiectasis

BACKGROUND

Nontuberculous mycobacteria are environmental organisms that are increasingly causing chronic and debilitating pulmonary infections, of which Mycobacterium avium complex (MAC) is the most common pathogen. MAC pulmonary disease (MAC-PD) is often difficult to treat, often requiring long-term multidrug antibiotic therapy.

RESEARCH QUESTION

Is there an association between various guideline-based three-drug therapy (GBT) regimens and (1) therapy-associated adverse events or (2) regimen change/discontinuation, within 12 months of therapy initiation?

STUDY DESIGN AND METHODS

In a retrospective cohort study, we examined tolerability outcomes of GBT regimens for MAC-PD in 4,626 US Medicare beneficiaries with bronchiectasis, who were prescribed a GBT as initial antibiotic treatment for presumed MAC-PD during 2006 to 2014. Using multivariable Cox proportional hazard regression, we estimated adjusted hazard ratios (aHRs) to compare the risk of adverse events and regimen change/discontinuations within 12 months of therapy initiation in various GBT regimens.

RESULTS

The cohort had a mean age ± SD of 77.9 ± 6.1 years at treatment start, were mostly female (77.7%), and were mostly non-Hispanic White (87.2%). The risk of regimen change/discontinuation within 12 months of therapy was higher for clarithromycin-based regimens than azithromycin-based regimens (aHR, 1.12; 95% CI, 1.04-1.20 with rifampin; aHR, 1.11; 95% CI, 0.93-1.32 with rifabutin as the companion rifamycin), and for rifabutin-containing regimens than rifampin-containing regimens (aHR, 1.49; 95% CI, 1.33-1.68 with azithromycin; aHR, 1.47; 95% CI, 1.27-1.70 with clarithromycin as the companion macrolide). The aHR comparing regimen change/discontinuation with clarithromycin-ethambutol-rifabutin and azithromycin-ethambutol-rifampin was 1.64 (95% CI, 1.43-1.64).

INTERPRETATION

Overall, an azithromycin-based regimen was less likely to be changed or discontinued than a clarithromycin-based regimen, and a rifampin-containing regimen was less likely to be changed or discontinued than a rifabutin-containing regimen within 12 months of therapy start. Our work provides a population-based assessment on the tolerability of multidrug antibiotic regimens used for the treatment of MAC-PD.

Prevalence and Characteristics of Non-tuberculous Mycobacteria (NTM) Infection in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation: a Systematic Review and Meta-analysis

PURPOSE

Non-tuberculous mycobacteria (NTM) infections in hematopoietic stem cell transplantation (HSCT) recipients represent a diagnostic and therapeutic challenge. Here, we aimed to review and analyze current literature on incidence, clinical presentation, and outcome of NTM infection after allogeneic HSCT.

METHODS

We performed a systematic review and meta-analysis of available literature regarding NTM infection in children and adults receiving allogeneic HSCT.

RESULTS

We identified 56 articles eligible for the analysis. Among 15 studies, describing 15,798 allogeneic HSCT, we estimated a prevalence of 1.26% (95% CI 0.72, 1.93) of NTM after transplant. Analysis of 175 patients with NTM infection showed a median time of diagnosis of 318 days after HSCT, an increased prevalence in adults (82.9%), and a most frequent pulmonary involvement (44%). Comparison between children and adults revealed an earlier post-transplant disease onset (median 130 days vs 287 days) and most frequent non-pulmonary presentation in children. A vast heterogeneity of therapeutic approach reflected the lack of universal recommendations regarding drug combination and duration of therapy. Overall, NTM-related mortality accounted for 33% in this systematic review.

CONCLUSION

Although rare, NTM infections can complicate post-transplant course with a high mortality rate in children and adults. The lack of prospective studies and guidelines prevents identification of risk factors and therapeutic recommendations.

Evaluation of Mycobacterium Avium Complex Pulmonary Disease Treatment Completion and Adherence to ATS/IDSA Guidelines

BACKGROUND

Nontuberculous mycobacteria are environmental organisms that cause infections leading to chronic, debilitating pulmonary disease, among which Mycobacterium avium complex (MAC) is the most common species.

METHODS

We described patterns of macrolide-based multidrug antibiotic therapies for MAC pulmonary disease (MAC-PD) in US Medicare beneficiaries with bronchiectasis between January 2006 and December 2014. MAC therapy was defined as a multidrug regimen containing a macrolide plus ≥1 other drug targeting MAC-PD (rifamycin, ethambutol, fluoroquinolone, or amikacin) prescribed concomitantly for >28 days.

RESULTS

We identified 9189 new MAC therapy users, with a mean age (standard deviation) of 74 (6 years) at the start of therapy; 75% female and 87% non-Hispanic white. A guideline-based regimen (a macrolide, ethambutol, and rifamycin, with or without amikacin) was prescribed for 51% of new MAC therapy users at treatment start, of whom 41% were continuing guideline-based therapy at 6 months, and only 18% at 12 months. Of all new MAC therapy users, by 18 months only 11% were still receiving MAC treatment, 55% had discontinued therapy, and 34% were censored owing to death or the end of the study period.

CONCLUSIONS

Overall, nearly half of new MAC therapy users were prescribed a non-guideline-recommended macrolide-based therapy, including regimens commonly associated with promoting macrolide resistance. Treatment discontinuation was common, and once discontinued, only a few beneficiaries resumed therapy at a later time. Our study adds important data to the current literature on treatment patterns for MAC-PD among older US populations. Future research should examine treatment patterns using more contemporary data sources.

Prevalence of nontuberculous mycobacteria and high efficacy of d-cycloserine and its synergistic effect with clarithromycin against Mycobacterium fortuitum and Mycobacterium abscessus

Background

The prevalence of pulmonary disease caused by nontuberculous mycobacteria (NTM) is reportedly on the rise in the world. Some of the species are resistant to various antibiotics; hence, limited treatment options are available. The aims of this study were to investigate the prevalence of NTM and to determine the effect of d-cycloserine against Mycobacterium fortuitum and Mycobacterium abscessus isolated from clinical specimens to find out the synergistic effect of d-cycloserine and clarithromycin.

Methods

A total of 95 nonduplicate pulmonary isolates of NTM were collected from three major Regional Tuberculosis (TB) Centers. NTM isolates were identified by conventional tests and PCR sequence analysis of the rpoB gene. PCR sequencing of erm-41 was performed for detecting the inducible resistance to macrolides. In vitro susceptibilities and activities of d-cycloserine-clarithromycin combinations were accessed using the broth microdilution method.

Results

Among 714-positive acid-fast bacilli from TB-suspected cases, 95 isolates were identified as NTM (13.3%). The prevalence of identified isolates was as follows: M. fortuitum 46 (48.4%), Mycobacterium simiae 16 (16.8%), Mycobacterium kansasii 15 (15.7%), M. abscessus 7 (7.3%), Mycobacterium thermoresistibile 4 (4.2%), Mycobacterium elephantis 3 (3.2%), Mycobacterium porcinum 2 (2.1%), and Mycobacterium chimaera 2 (2.1%). In addition, rpoB sequence analysis could identify all NTM isolates. The effect of d-cycloserine was better than that of clarithromycin. The synergistic effect of d-cycloserine with clarithromycin was observed for six (100%) and five (71.5%) strains of M. fortuitum and M. abscessus, respectively.

Conclusion

In the present study, we demonstrated a wide range of NTM in processed samples from different provinces of Iran. Our observations indicated that d-cycloserine was very active against M. abscessus and M. fortuitum; hence, d-cycloserine, either alone or in combination with clarithromycin, may be promising for the treatment of M. abscessus- and M. fortuitum-associated diseases.

Drug Susceptibility Testing of 31 Antimicrobial Agents on Rapidly Growing Mycobacteria Isolates from China

Objectives. Several species of rapidly growing mycobacteria (RGM) are now recognized as human pathogens. However, limited data on effective drug treatments against these organisms exists. Here, we describe the species distribution and drug susceptibility profiles of RGM clinical isolates collected from four southern Chinese provinces from January 2005 to December 2012. Methods. Clinical isolates (73) were subjected to in vitro testing with 31 antimicrobial agents using the cation-adjusted Mueller-Hinton broth microdilution method. The isolates included 55 M. abscessus, 11 M. fortuitum, 3 M. chelonae, 2 M. neoaurum, and 2 M. septicum isolates. Results. M. abscessus (75.34%) and M. fortuitum (15.07%), the most common species, exhibited greater antibiotic resistance than the other three species. The isolates had low resistance to amikacin, linezolid, and tigecycline, and high resistance to first-line antituberculous agents, amoxicillin-clavulanic acid, rifapentine, dapsone, thioacetazone, and pasiniazid. M. abscessus and M. fortuitum were highly resistant to ofloxacin and rifabutin, respectively. The isolates showed moderate resistance to the other antimicrobial agents. Conclusions. Our results suggest that tigecycline, linezolid, clofazimine, and cefmetazole are appropriate choices for M. abscessus infections. Capreomycin, sulfamethoxazole, tigecycline, clofazimine, and cefmetazole are potentially good choices for M. fortuitum infections. Our drug susceptibility data should be useful to clinicians.

Identification and characterization of non-tuberculous mycobacteria isolated from tuberculosis suspects in Southern-central China

The incidence of non-tuberculous mycobacteria (NTM)-related death has increased globally recently. To obtain information of the species and characterization of pathogens involved in NTM pulmonary infection in Southern-central China, we identified 160 non-tuberculous infection cases from 3995 acid-fast bacilli (AFB)-positive tuberculous suspects. We then randomly selected 101 non-tuberculous patients, isolated bacteria from their sputa and genotyped the pathogens using the 16S rRNA gene and 16S-23S rRNA internal transcribed spacer sequences. M. intracellulare (32.67%, 33/101), M. abscessus (32.67%, 33/101) and M. fortuitum (7.92%, 8/101) are identified in these isolates. Surprisingly, non-mycobacteria including Gordonia (8.91%, 9/101), Nocardia (5.94%, 6/101) and Tsukamurella (0.99%, 1/101) are also discovered, and the case of Tsukamurella pulmonis infection is first discovered in Southern-central China. Moreover, species of M. mucogenicum group, M. chubuense, M. kansasii, M. gastri, M. avium, M. porcinum and M. smegmatis are identified. In addition, nine immune compromised cases (8.91%, 9/101), including type two diabetes mellitus and HIV/AIDS are found to be infected with non-tuberculous bacteria. This study revealed the distribution and characteristics of non-tuberculous AFB pathogen infection occurred in Southern-central China, and suggested that physicians should be alert of the emerging of NTM and non-mycobacteria infection in AFB positive cases and take caution when choosing chemotherapy for tuberculosis-like pulmonary infections. Generally, this study may help with the development of new strategy for the diagnosis and treatment of mycobacterial infection.

Antimicrobial susceptibility and molecular characterization of Mycobacterium intracellulare in China

Mycobacterium avium complex (MAC) is the most common non-tuberculosis mycobacterial pathogen isolated from respiratory samples, mainly including two species, Mycobacterium avium (M. avium) and Mycobacterium intracellulare (M. intracellulare). Although these two species belong to the same group, M. avium and M. intracellulare reveal significantly differences in pathogenicity and biology. Nevertheless, little is known regarding the drug resistant details profile of M. avium or M. intracellulare instead of MAC. Here, we examined the antimicrobial susceptibility profiles of 52 clinical M. intracellulare isolates against fourteen antimicrobial agents, which are widely selected for the treatment of nontuberculous mycobacteria (NTM) infection. The drug susceptibility test revealed that clarithromycin (47/52, 90.4%), rifampicin (41/52, 78.8%) and capreomycin (40/52, 76.9%) revealed highly antimicrobial activities against M. intracellulare isolates in vitro. Furthermore, all clarithromycin resistant isolates harbored mutations in the 23S rRNA gene, and the percentage of amikacin resistant ones with mutation in the rrs gene is 62.5% (10/16). The Hunter-Gaston Discriminatory Index (HGDI) value for the 16-loci Variable Number of Tandem Repeat (VNTR) typing of M. intracellulare isolates was 0.994, and M. intracellulare resistance to moxifloxacin was significantly more commonly found in clustered strains than in nonclustered strains (χ(2)=5.551, P=0.040). In conclusion, our data demonstrated that clarithromycin and capreomycin revealed highly antimicrobial activities against M. intracellulare isolates, and clarithromycin and amikacin resistance could be detected more readily and rapidly using molecular scanning of corresponding drug target than conventional drug susceptibility testing. We also found that infection by clustered strains was significantly associated with resistance to moxifloxacin.

Critical pulmonary infection due to nontuberculous mycobacterium in pediatric leukemia: report of a difficult diagnosis and review of pediatric series

Nontuberculous mycobacterial infections are rare but severe complications of chemotherapy in children. In children with prolonged lymphopoenia after mieloablative regimens, symptoms can be nonspecific and fever and pulmonary impairment are the most common clinical features. Diagnosis is challenging for physicians and microbiologists and often requires invasive techniques. We report a girl affected by acute lymphoblastic leukemia, who developed a disseminated infection sustained by Mycobacterium avium complex. Identification of the microorganism was obtained by open lung biopsy and evidence of mycobacterium genome. We also reviewed 15 literature cases of disseminated infections of nontuberculous mycobacterium in children with leukemia.

Sulfatase-activated fluorophores for rapid discrimination of mycobacterial species and strains

Most current diagnostic tests for tuberculosis do not reveal the species or strain of pathogen causing pulmonary infection, which can lead to inappropriate treatment regimens and the spread of disease. Here, we report an assay for mycobacterial strain assignment based on genetically conserved mycobacterial sulfatases. We developed a sulfatase-activated probe, 7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one)-sulfate, that detects enzyme activity in native protein gels, allowing the rapid detection of sulfatases in mycobacterial lysates. This assay revealed that mycobacterial strains have distinct sulfatase fingerprints that can be used to judge both the species and lineage. Our results demonstrate the potential of enzyme-activated probes for rapid pathogen discrimination for infectious diseases.