Nontuberculous mycobacterial lung disease prevalence at four integrated health care delivery systems

Increasing nontuberculous mycobacteria reporting rates and species diversity identified in clinical laboratory reports

Background

Nontuberculous Mycobacteria (NTM) are environmental microorganisms that can affect human health. A 2009–2010 occurrence survey of NTM in potable tap water samples indicated an increased recovery rate for many clinically significant species such as M. avium (30%) and M. abscessus (12%). To determine if these trends by species were mirrored in human infections, isolation rates of NTM species identified in clinical laboratory reports from four states were evaluated.

Method

Clinical laboratory reports from the Mississippi, Missouri, Ohio, and Wisconsin Health Departments were used to investigate the species of NTM isolated from human specimens in 2014. The NTM positive specimen reports were tabulated for each species and complex/group. The number of reports by month were used to investigate seasonal trends. The 2014 isolation rates were compared to historic values to examine longitudinal trends.

Results

The positive rate of NTM specimens increased from 8.2 per 100,000 persons in 1994 to 16 per 100,000 persons in 2014 (or 13.3 per 100,000 after excluding Mycobacterium gordonae). Changes in NTM diversity were observed in complex/groups known to be clinically significant. Between 1994 and 2014 the rate implicating M. abscesses-chelonae group and M. avium complex increased by 322 and 149%, respectively.

Conclusions

Based on public health data supplied by the four State’s Health Departments and the 2014 U.S. population, 50,976 positive NTM specimen reports per year were projected for the nation; serving as an indicator for the national potential disease burden that year.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3043-7) contains supplementary material, which is available to authorized users.

NTM drug discovery: status, gaps and the way forward

Incidence of pulmonary diseases caused by non-tuberculous mycobacteria (NTM), relatives of Mycobacterium tuberculosis, is increasing at an alarming rate, surpassing tuberculosis in many countries. Current chemotherapies require long treatment times and the clinical outcomes are often disappointing. There is an urgent medical need to discover and develop new, more-efficacious anti-NTM drugs. In this review, we summarize the current status of NTM drug development, and highlight knowledge gaps and scientific obstacles in NTM drug discovery. We propose strategies to reduce biological uncertainties and to begin to populate a NTM drug pipeline with attractive leads and drug candidates.

Species-Specific Risk Factors, Treatment Decisions, and Clinical Outcomes for Laboratory Isolates of Less Common Nontuberculous Mycobacteria in Washington State

RATIONALE

Nontuberculous mycobacteria (NTM) are a diverse group of environmental organisms that infrequently cause human disease. Understanding of the epidemiologic and clinical characteristics associated with NTM disease is needed to refine diagnostic and treatment strategies, particularly among the less commonly isolated species.

OBJECTIVES

To improve knowledge of geographic variance of NTM species, to correlate detailed clinical information with isolation of specific NTM, and to examine the decision to treat and outcomes for specific NTM.

METHODS

Mycobacterial cultures submitted to the University of Washington mycobacterial laboratory from 1998 to 2011 were examined. We report isolation frequency and demographic information from all samples with clinical variables. We also examined treatment decisions and outcomes in a subset of patients with Mycobacterium abscessus complex, Mycobacterium chelonae, Mycobacterium fortuitum, Mycobacterium gordonae, Mycobacterium kansasii, Mycobacterium lentiflavum, Mycobacterium porcinum, and Mycobacterium xenopi.

RESULTS

Cultures of NTM were available from 3,470 patients, 937 of whom had clinical data available. When we compared patients born within or outside Washington State, we found that the mycobacterial species frequency varied. Among 168 patients with one of the studied environmental mycobacteria, 72% had major comorbid conditions. Bronchiectasis was common among patients with pulmonary isolation of any NTM, including those with nonpathogenic M. gordonae. Although mortality was high (37%), few deaths were directly attributable to mycobacterial infection. Among 56 patients who met American Thoracic Society criteria for NTM lung disease, 22 were treated, and 19 of those had M. abscessus complex and M. kansasii. The treatment regimens used tended to follow published guidelines.

CONCLUSIONS

Isolation of NTM varied by geographic region of origin and location within Washington State. Several clinical risk factors were specific to individual species. Comorbid conditions were common in patients with and without mycobacterial disease. Among patients with one of the studied organisms, there was a high mortality rate more frequently related to comorbid conditions than to mycobacterial disease.

Long-Term Outcomes in a Population-based Cohort with Respiratory Nontuberculous Mycobacteria Isolation

RATIONALE

The natural history of nontuberculous mycobacteria (NTM) respiratory infection in the general population is poorly understood.

OBJECTIVES

To describe the long-term clinical, microbiologic, and radiographic outcomes of patients with respiratory NTM isolates.

METHODS

We previously identified a population-based cohort of patients with respiratory NTM isolation during 2005-2006 and categorized patients as cases or noncases using the American Thoracic Society/Infectious Diseases Society of America pulmonary NTM disease criteria at that time. During 2014-2015, we reviewed medical charts of patients alive on January 1, 2007. Outcomes of interest were the proportion of baseline noncases who later met case criteria and the proportions of patients with culture conversion or findings consistent with persistent disease at least 2-5 years and at least 5 years after first isolation. We defined disease persistence radiographically as infiltrate, nodules, or cavities and microbiologically as a positive respiratory mycobacterial culture. We used logistic regression to evaluate factors associated with evidence of persistence.

RESULTS

The study included 172 patients (62% of 278 eligible); those not included either refused consent (n = 47) or were not located (n = 56). One hundred two (59%) included patients met case criteria at baseline. Mycobacterium avium complex was commonly isolated among baseline cases (n = 91 [89%]) and noncases (n = 52 [74%]). Overall, 57 (55%) baseline cases had died, as compared with 43 (61%) noncases (P = 0.47). Among baseline noncases, only four (5.7%) later met case criteria. Overall, 55 (54%) baseline cases and 6 (9%) noncases initiated NTM treatment. Among cases, cultures were converted in 25 (64.1%) treated versus 4 (40%) untreated patients (P = 0.04). Of 89 cases alive 2 years after isolation, 61 (69%) had additional radiography, and 35 (39%) had respiratory cultures. Of these individuals, 54 (89%) had radiographic evidence and 17 (49%) had microbiologic evidence of disease persistence. At 5 years after first isolation these figures were 36 (82%) and 13 (54%), respectively. Women were more likely to have persistent radiographic findings and microbiologic persistence, and patients with chronic obstructive pulmonary disease were less likely to have microbiologic persistence.

CONCLUSIONS

In the general population, follow-up beyond 2 years of patients with respiratory NTM isolation is limited. Among those with additional evaluations, at least half of individuals have persistent positive cultures or radiographic findings consistent with NTM at least 2 years after isolation.

Antibiotic Susceptibility and Genotyping of Mycobacterium avium Strains That Cause Pulmonary and Disseminated Infection

Mycobacterium avium subsp. hominissuis mainly causes disseminated infection in immunocompromised hosts, such as individuals with human immunodeficiency virus (HIV) infection, and pulmonary infection in immunocompetent hosts. However, many aspects of the different types of M. avium subsp. hominissuis infection remain unclear. We examined the antibiotic susceptibilities and genotypes of M. avium subsp. hominissuis isolates from different hosts by performing drug susceptibility testing using eight antibiotics (clarithromycin, rifampin, ethambutol, streptomycin, kanamycin, amikacin, ethionamide, and levofloxacin) and variable-number tandem-repeat (VNTR) typing analysis for 46 isolates from the sputa of HIV-negative patients with pulmonary M. avium subsp. hominissuis disease without previous antibiotic treatment and 30 isolates from the blood of HIV-positive patients with disseminated M. avium subsp. hominissuis disease. Interestingly, isolates from pulmonary M. avium subsp. hominissuis disease patients were more resistant to seven of the eight drugs, with the exception being rifampin, than isolates from HIV-positive patients. Moreover, VNTR typing analysis showed that the strains examined in this study were roughly classified into three clusters, and the genetic distance from reference strain 104 for isolates from pulmonary M. avium subsp. hominissuis disease patients was statistically significantly different from that for isolates from HIV-positive patients (P = 0.0018), suggesting that M. avium subsp. hominissuis strains that cause pulmonary and disseminated disease have genetically distinct features. Significant differences in susceptibility to seven of the eight drugs, with the exception being ethambutol, were noted among the three clusters. Collectively, these results suggest that an association between the type of M. avium subsp. hominissuis infection, drug susceptibility, and the VNTR genotype and the properties of M. avium subsp. hominissuis strains associated with the development of pulmonary disease are involved in higher levels of antibiotic resistance.

Pulmonary Nontuberculous Mycobacteria-Associated Deaths, Ontario, Canada, 2001-2013

Survival implications of nontuberculous mycobacterial pulmonary disease (NTM-PD) and NTM pulmonary isolation without disease (NTM-PI) are unclear. To study deaths associated with NTM-PD and NTM-PI and differences in survival between them, we conducted a population-based cohort study of persons with microbiologically defined NTM-PD or NTM-PI diagnosed during 2001–2013 in Ontario, Canada. We used propensity score matching and Cox proportional hazards models to compare survival. Among 9,681 NTM-PD patients and 10,936 NTM-PI patients, 87% and 91%, respectively, were successfully matched with unexposed controls. Both NTM-PD and NTM-PI were associated with higher rates of death for all species combined and for most individual species. Compared with NTM-PI, NTM-PD was associated with higher death rates for all species combined, Mycobacterium avium complex, and M. xenopi. NTM-PD and NTM-PI were significantly associated with death, NTM-PD more so than NTM-PI.

Epidemiology of Nontuberculous Mycobacterial Lung Disease and Tuberculosis, Hawaii, USA

Previous studies found Hawaiians and Asian-Americans/Pacific Islanders to be independently at increased risk for nontuberculous mycobacterial pulmonary disease (NTMPD) and tuberculosis (TB). To better understand NTM infection and TB risk patterns in Hawaii, USA, we evaluated data on a cohort of patients in Hawaii for 2005–2013. Period prevalence of NTMPD was highest among Japanese, Chinese, and Vietnamese patients (>300/100,000 persons) and lowest among Native Hawaiians and Other Pacific Islanders (50/100,000). Japanese patients were twice as likely as all other racial/ethnic groups to have Mycobacterium abscessus isolated (adjusted odds ratio 2.0, 95% CI 1.2–3.2) but were not at increased risk for infection with other mycobacteria species. In contrast, incidence of TB was stable and was lowest among Japanese patients (no cases) and highest among Filipino, Korean, and Vietnamese patients (>50/100,000). Substantial differences exist in the epidemiology of NTMPD by race/ethnicity, suggesting behavioral and biologic factors that affect disease susceptibility.

Pulmonary Cavity From Mycobacterium malmoense in an HIV-Infected Patient: Complicated by Bronchopleural Fistula

We present a case of M. malmoense and HIV co-infection complicated by aspergilloma leading to bronchopleural fistula with intractable pneumothorax and pleural aspergillosis, ultimately requiring surgical intervention. Treatment guidelines for M. malmoense are reviewed, literature regarding M. malmoense and HIV co-infection is reviewed, and the epidemiology of M. malmoense in North America is discussed.

On the Reportability of Nontuberculous Mycobacterial Disease to Public Health Authorities

Nontuberculous mycobacteria (NTM) are environmental pathogens that are an increasingly common cause of pulmonary and extrapulmonary disease. Electronic laboratory-based reporting is a straightforward mechanism for identifying NTM infections and for monitoring trends in disease. Oregon was the first state to make NTM reportable, although at this time the reporting requirement is limited to extrapulmonary infection. This has assisted authorities in detecting outbreaks and healthcare-related infections. However, further consideration should be given to the reportability of pulmonary NTM disease. Pulmonary NTM disease is more common than tuberculosis in the United States and is of emerging public health concern. Although the direct public health action that would be triggered by a pulmonary NTM disease report is not clear, without surveillance, public health is missing an opportunity to better understand pulmonary NTM disease trends and reasons for its increasing recognition within our population. We believe state health authorities should conduct surveillance for pulmonary NTM, either by mandating reporting of laboratory isolates or by other mechanisms as we have done in Oregon.

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

Objectives

To perform a systematic review and meta-analysis of the level of funding support and the sputum culture conversion rates in pulmonary Mycobacterium avium-intracellulare complex (P-MAC) disease in adult patients without cystic fibrosis or HIV infection, treated with recommended antibiotic regimens.

Methods

We performed a literature search to identify clinical trials, prospective studies and registries that reported outcomes in P-MAC patients. Studies that reported P-MAC diagnosis and treatments based on established guidelines met the inclusion criteria and were examined for bias and quality. We modified existing quality scales and came up with a 10 star quality score. Outcomes meta-analysed were sputum conversion incidence ratios (IR) and their 95% CI, weighted for study quality.

Results

Twenty-one studies that examined 28 regimens, including 2534 patients in intent-to-treat analyses and 1968 in per-protocol analyses, were identified. The study quality mean ± SD scores were 5.4 ± 2.2 out of 10 stars. Only two (9.5%) studies received public funding. There was significant heterogeneity of microbial effect among treatment regimens (I2 > 40%; P > 0.001). The pooled IR for sustained sputum conversion was 0.54 (95% CI 0.45-0.63) for macrolide-containing regimens versus 0.38 (0.25-0.52) with macrolide-free regimens. Prolonging therapy duration beyond 12 months was associated with an average decline in sputum conversion to 22% (95% CI 1%-44%).

Conclusions

Researchers working on P-MAC therapy have received very little public funding support. As a result, the evidence base for treatment guidelines is based on studies of relatively small numbers of patients in low-quality studies. Nevertheless, these studies showed poor sputum conversion rates in patients receiving recommended treatment regimens.

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.

Prevalence of Nontuberculous Mycobacterial Pulmonary Disease, Germany, 2009-2014

We analyzed routine statutory health insurance claim data to determine prevalence of nontuberculous mycobacterial pulmonary disease in Germany. Documented prevalence rates of this nonnotifiable disease increased from 2.3 to 3.3 cases/100,000 population from 2009 to 2014. Prevalence showed a strong association with advanced age and chronic obstructive pulmonary disease.

Patient-Centered Research Priorities for Pulmonary Nontuberculous Mycobacteria (NTM) Infection. An NTM Research Consortium Workshop Report

Nontuberculous mycobacteria (NTM) cause an increasingly important chronic and debilitating lung disease in older adults. Diagnosis is often delayed, although awareness among clinicians and patients is increasing. When necessary, treatment often lasts 18-24 months and consists of three or four antibiotics that can have serious side effects. Relapses are common and commonly require resumption of prolonged therapy. Given the need for improved diagnostic techniques and clinical trials to identify new therapies or to improve existing therapies, a group of North American clinicians and researchers formed the NTM Research Consortium (NTMRC) in 2014. The NTMRC recognized the importance of including the patient voice in determining research priorities for NTM. In November 2015, patients, caregivers, patient advocates, clinical experts, and researchers gathered for a 1-day meeting in Portland, Oregon funded by the Patient-Centered Outcomes Research Institute. The meeting goal was to define patient-centered research priorities for NTM lung infections. Patients expressed frustration with the number of people who have endured years of missed diagnoses or inadequate treatment of NTM. Participants identified as top research priorities the prevention of NTM infection; approval of more effective treatments with fewer side effects and easier administration; understanding the best chest physiotherapy methods; validating and using tools to measure quality of life; and developing a disease-specific activity and severity assessment tool. Workshop participants agreed that two complementary objectives are critical to ensure the best achievable outcomes for patients: (1) additional clinician education to improve screening and diagnosis of NTM infections; and (2) development of a geographically distributed network of experts in NTM disease to offer consultation or direct therapy after a diagnosis is made.

Deaths Related to Nontuberculous Mycobacterial Infections in the United States, 1999-2014

RATIONALE

Unlike tuberculosis, nontuberculous mycobacterial disease is not reportable to public health authorities in the United States, and the total burden of disease is uncertain.

OBJECTIVES

To estimate the mortality of nontuberculous mycobacterial disease in the United States over a 15-year period and to identify temporal trends.

METHODS

The U.S. Multiple Cause of Death Files from 1999 through 2014 were searched for a listing of nontuberculous mycobacterial disease by International Classification of Diseases, Tenth Revision code as either the underlying or a contributing cause of death. Characteristics of individuals with nontuberculous mycobacteria-related deaths in the United States were summarized according to demographic characteristics. Age-adjusted mortality rates and rate ratios were calculated using bridged-race population estimates of U.S. census population data. Time trends were evaluated with negative binomial regression.

MEASUREMENTS AND MAIN RESULTS

There was a significant increase in nontuberculous mycobacteria-related deaths among individuals without a diagnosis of HIV infection (P = 0.004). Mortality rates increased with advancing age. Age-adjusted mortality rate ratios were lower for men (risk ratio [RR], 0.84; 95% confidence interval [CI], 0.80-0.87) compared with women, and were lower for Hispanic individuals (RR, 0.53; 95% CI, 0.49-0.56) and black, non-Hispanic persons (RR, 0.83; 95% CI, 0.77-0.88) compared with white, non-Hispanic individuals.

CONCLUSIONS

The mortality rate of nontuberculous mycobacterial disease among HIV-uninfected individuals has increased in the United States between 1999 and 2014. These deaths occurred disproportionately in older white women. Considering the concurrent decline in tuberculosis-related deaths, these findings demonstrate a shift in the epidemiology of fatal mycobacterial infections in the United States.

Whole-Exome Sequencing Identifies the 6q12-q16 Linkage Region and a Candidate Gene, TTK, for Pulmonary Nontuberculous Mycobacterial Disease

RATIONALE

Pulmonary nontuberculous mycobacterial disease (PNTM) often affects white postmenopausal women, with a tall and lean body habitus and higher rates of scoliosis, pectus excavatum, mitral valve prolapse, and mutations in the CFTR gene. These clinical features and the familial clustering of the disease suggest an underlying genetic mechanism.

OBJECTIVES

To map the genes associated with PNTM, whole-exome sequencing was conducted in 12 PNTM families and 57 sporadic cases recruited at the National Institutes of Health Clinical Center during 2001-2013.

METHODS

We performed a variant-level and a gene-level parametric linkage analysis on nine PNTM families (16 affected and 20 unaffected) as well as a gene-level association analysis on nine PNTM families and 55 sporadic cases.

MEASUREMENTS AND MAIN RESULTS

The genome-wide variant-level linkage analysis using 4,328 independent common variants identified a 20-cM region on chromosome 6q12-6q16 (heterogeneity logarithm of odds score = 3.9), under a recessive disease model with 100% penetrance and a risk allele frequency of 5%. All genes on chromosome 6 were then tested in the gene-level linkage analysis, using the collapsed haplotype pattern method. The TTK protein kinase gene (TTK) on chromosome 6q14.1 was the most significant (heterogeneity logarithm of odds score = 3.38). In addition, the genes MAP2K4, RCOR3, KRT83, IFNLR1, and SLC29A1 were associated with PNTM in our gene-level association analysis.

CONCLUSIONS

The TTK gene encodes a protein kinase that is essential for mitotic checkpoints and the DNA damage response. TTK and other genetic loci identified in our study may contribute to the increased susceptibility to NTM infection and its progression to pulmonary disease.

Higher-than-expected prevalence of non-tuberculous mycobacteria in HIV setting in Botswana: Implications for diagnostic algorithms using Xpert MTB/RIF assay

Background

Non-tuberculous mycobacteria (NTM) can cause pulmonary infection and disease especially among people living with HIV (PLHIV). PLHIV with NTM disease may clinically present with one of the four symptoms consistent with tuberculosis (TB). We describe the prevalence of NTM and Mycobacterium tuberculosis complex (MTBC) isolated among PLHIV who presented for HIV care and treatment.

Methods

All PLHIV patients presenting for HIV care and treatment services at 22 clinical sites in Botswana were offered screening for TB and were recruited. Patients who had ≥1 TB symptom were asked to submit sputa for Xpert MTB/RIF and culture. Culture growth was identified as NTM and MTBC using the SD-Bioline TB Ag MPT64 Kit and Ziehl Neelsen microscopy. NTM and MTBC isolates underwent species identification by the Hain GenoType CM and AS line probe assays.

Results

Among 16, 259 PLHIV enrolled 3068 screened positive for at least one TB symptom. Of these, 1940 submitted ≥1 sputum specimen, 427 (22%) patients had ≥1 positive-culture result identified phenotypically for mycobacterial growth. Of these 247 and 180 patients were identified as having isolates were NTM and MTBC, respectively. Of the 247 patients identified with isolates containing NTM; 19 were later excluded as not having NTM based on additional genotypic testing. Among the remaining 408 patients 228 (56%, 95% confidence interval, 46–66%) with NTM. M. intracellulare was the most common isolated (47.8%). Other NTMs commonly associated with pulmonary disease included M. malmoense (3.9%), M. avium (2.2%), M. abscessus (0.9%) and M. kansasii (0.4%). After excluding NTM isolates that were non-speciated and M. gordonae 154 (67.5%) of the NTM isolates were potential pathogens.

Conclusions

In the setting of HIV care and treatment, over-half (56%) of a positive sputum culture among PLHIV with TB symptoms was NTM. Though we were not able to distinguish in our study NTM disease and colonization, the study suggests culture and species identification for PLHIV presenting with TB symptoms remains important to facilitate NTM diagnosis and hasten time to appropriate treatment.

Epidemiology and Predictors of NTM Pulmonary Infection in Taiwan - a Retrospective, Five-Year Multicenter Study

Multicenter, longitudinal studies on nontuberculous mycobacteria (NTM) pulmonary infection (PI) are lacking. This study provides a 5-year epidemiological overview of NTM-PI in Taiwan and investigated its predictors. The clinical relevance of each respiratory NTM isolate in six hospitals between 2008 and 2014 was determined according to current guidelines. Recurrent episodes were judged by serial bacteriological results. New episodes of NTM-PI and pulmonary colonization (PC) occurring since 2010 were analyzed. Logistic regression analysis was performed to identify the predictors of NTM-PI. Between 2010 and 2014, the incidence rate of NTM-PI was 46.0 episodes per 100,000 hospital-based patient-years. Mycobacterium avium intracellulare complex (MAC) was predominant in Northern Taiwan, whereas MAC and M. abscessus were copredominant in Southern Taiwan. Multiple episodes occurred in 9.5% of NTM-PI patients. No female predominance was observed, except for MAC-PI. Previous pulmonary tuberculosis and chronic obstructive pulmonary disease (COPD) were the most common pulmonary comorbidities and independent risk factors for NTM-PI. Other risk factors included M. kansasii, M. abscessus, and southern Taiwan. Geographical variation of NTM-PI exists in Taiwan. Clinicians should keep a high suspicion on NTM-PI in the risk population. In endemic area of tuberculosis and COPD, there may be no female predominance in NTM-PI.

Nontuberculous mycobacterial infection in rheumatoid arthritis patients: a single-center experience in South Korea

BACKGROUND/AIMS

Nontuberculous mycobacteria (NTM) infection has been increasing worldwide in both general population and immunocompromised patients, which has also been reported in rheumatoid arthritis (RA) patients. This study aimed to identify the incidence and clinical characteristics of NTM infection in RA patients living in tuberculosis (TB) infection endemic area.

METHODS

We performed a retrospective analysis of NTM infection cases in our RA registry at a tertiary referral center from January 1995 to December 2013. The clinical features of them were compared to those of 52 TB infection patients from same registry.

RESULTS

Among 1,397 patients with RA, NTM infection was newly developed in 26 patients and the incidence of NTM infection was 164.8 per 100,000 patient-years. The Mycobacterium avium complex was the most frequent isolate (76.9%). None of the NTM infections had extrapulmonary involvement, which was rather common in TB infection (26.9%). Patients with NTM infection were older, received higher cumulative steroid doses, and had higher rates of past TB infection history and concomitant interstitial lung disease (ILD) than cases with TB infection.

CONCLUSIONS

In South Korea, NTM infection is not rare in RA patients, and infection rates are growing. Physicians should be cautious about NTM infection in patients with a history of TB infection or concomitant ILD, even living in TB endemic area.

Mycobacterium abscessus WhiB7 Regulates a Species-Specific Repertoire of Genes To Confer Extreme Antibiotic Resistance

Mycobacterium abscessus causes acute and chronic bronchopulmonary infection in patients with chronic lung damage, of which cystic fibrosis (CF) patients are particularly vulnerable. The major threat posed by this organism is its high intrinsic antibiotic resistance. A typical treatment regimen involves a 6- to 12-month-long combination therapy of clarithromycin and amikacin, with cure rates below 50% and multiple side effects, especially due to amikacin. In the present work, we show that M. abscessuswhiB7, a homologue of Mycobacterium tuberculosis and Mycobacterium smegmatis whiB7 with previously demonstrated effects on intrinsic antibiotic resistance, is strongly induced when exposed to clinically relevant antibiotics that target the ribosome: erythromycin, clarithromycin, amikacin, tetracycline, and spectinomycin. The deletion of M. abscessuswhiB7 results in sensitivity to all of the above-mentioned antibiotics. Further, we have defined and compared the whiB7 regulon of M. abscessus with the closely related nontuberculous mycobacterium (NTM) M. smegmatis to demonstrate the induction of a species-specific repertoire of genes. Finally, we show that one such gene, eis2, is specifically induced in M. abscessus by whiB7 and contributes to its higher levels of intrinsic amikacin resistance. This species-specific pattern of gene induction might account for the differences in drug susceptibilities to other antibiotics and between different mycobacterial species.

Bedaquiline Inhibits the ATP Synthase in Mycobacterium abscessus and Is Effective in Infected Zebrafish

Pulmonary infections caused by Mycobacterium abscessus are emerging as a global threat, especially in cystic fibrosis patients. Further intensifying the concern of M. abscessus infection is the recent evidence of human-to-human transmission of the infection. M. abscessus is a naturally multidrug-resistant fast-growing pathogen for which pharmacological options are limited. Repurposing antitubercular drugs represents an attractive option for the development of chemotherapeutic alternatives against M. abscessus infections. Bedaquiline (BDQ), an ATP synthase inhibitor, has recently been approved for the treatment of multidrug-resistant tuberculosis. Herein, we show that BDQ has a very low MIC against a vast panel of clinical isolates. Despite being bacteriostatic in vitro, BDQ was highly efficacious in a zebrafish model of M. abscessus infection. Remarkably, a very short period of treatment was sufficient to protect the infected larvae from M. abscessus-induced killing. This was corroborated with reduced numbers of abscesses and cords, considered to be major pathophysiological signs in infected zebrafish. Mode-of-action studies revealed that BDQ triggered a rapid depletion of ATP in M. abscessusin vitro, consistent with the drug targeting the F_oF₁ ATP synthase. Importantly, despite a failure to select in vitro for spontaneous mutants that are highly resistant to BDQ, the transfer of single nucleotide polymorphisms leading to D29V or A64P substitutions in atpE conferred high resistance, thus resolving the target of BDQ in M. abscessus Overall, this study indicates that BDQ is active against M. abscessusin vitro and in vivo and should be considered for clinical use against the difficult-to-manage M. abscessus pulmonary infections.

Natural course of the nodular bronchiectatic form of Mycobacterium Avium complex lung disease: Long-term radiologic change without treatment

BACKGROUND/PURPOSE

Although the incidence of Mycobacterium avium complex (MAC) lung disease is increasing, the long-term natural course of the nodular bronchiectatic form of MAC lung disease is not well described. The objective of our study is to evaluate long-term radiologic changes in untreated MAC lung disease by analyzing serial chest computed tomography (CT) scan findings.

METHODS

Of 104 patients with MAC lung disease, we selected 40 untreated nodular bronchiectatic MAC patients who underwent serial chest CTs without treatment for at least four years (mean = 6.23 years). Majority of patients have minimal symptoms. Two chest radiologists retrospectively reviewed initial and final chest CT scans. Each chest CT scan was scored for presence and extent of bronchiectasis, cellular bronchiolitis, consolidation, cavity, and nodule (maximum score: 30).

RESULTS

Of 40 patients, 39 (97.5%) experienced a significant increase in overall CT score (overall difference = 4.89, p<0.001). On repeated measure analysis of variance analysis, cavity yielded the largest increase compared with cellular bronchiolitis (p = 0.013), nodule (p<0.001), and consolidation (p = 0.004). However, there was no significant difference in mean score change between cavity and bronchiectasis (p = 0.073). In analysis between radiologic parameters and the absolute number of involved segments, bronchiectasis showed most significant change compared with nodule (p<0.001) and consolidation (p<0.001).

CONCLUSIONS

Most untreated nodular bronchiectatic MAC lung disease cases showed radiologic deterioration over long-term observation periods when we compared serial chest CT scans. Careful monitoring of MAC lung disease with serial chest CT scan can be beneficial in these untreated patients.

Pulmonary Tuberculosis: Role of Radiology in Diagnosis and Management

Tuberculosis is a public health problem worldwide, including in the United States-particularly among immunocompromised patients and other high-risk groups. Tuberculosis manifests in active and latent forms. Active disease can occur as primary tuberculosis, developing shortly after infection, or postprimary tuberculosis, developing after a long period of latent infection. Primary tuberculosis occurs most commonly in children and immunocompromised patients, who present with lymphadenopathy, pulmonary consolidation, and pleural effusion. Postprimary tuberculosis may manifest with cavities, consolidations, and centrilobular nodules. Miliary tuberculosis refers to hematogenously disseminated disease that is more commonly seen in immunocompromised patients, who present with miliary lung nodules and multiorgan involvement. The principal means of testing for active tuberculosis is sputum analysis, including smear, culture, and nucleic acid amplification testing. Imaging findings, particularly the presence of cavitation, can affect treatment decisions, such as the duration of therapy. Latent tuberculosis is an asymptomatic infection that can lead to postprimary tuberculosis in the future. Patients who are suspected of having latent tuberculosis may undergo targeted testing with a tuberculin skin test or interferon-γ release assay. Chest radiographs are used to stratify for risk and to assess for asymptomatic active disease. Sequelae of previous tuberculosis that is now inactive manifest characteristically as fibronodular opacities in the apical and upper lung zones. Stability of radiographic findings for 6 months distinguishes inactive from active disease. Nontuberculous mycobacterial disease can sometimes mimic the findings of active tuberculosis, and laboratory confirmation is required to make the distinction. Familiarity with the imaging, clinical, and laboratory features of tuberculosis is important for diagnosis and management. ^©RSNA, 2017.

Non-tuberculous Mycobacteria isolated from Pulmonary samples in sub-Saharan Africa - A Systematic Review and Meta Analyses

Pulmonary non-tuberculous mycobacterial (NTM) disease epidemiology in sub-Saharan Africa is not as well described as for pulmonary tuberculosis. Earlier reviews of global NTM epidemiology only included subject-level data from one sub-Saharan Africa country. We systematically reviewed the literature and searched PubMed, Embase, Popline, OVID and Africa Wide Information for articles on prevalence and clinical relevance of NTM detection in pulmonary samples in sub-Saharan Africa. We applied the American Thoracic Society/Infectious Disease Society of America criteria to differentiate between colonisation and disease. Only 37 articles from 373 citations met our inclusion criteria. The prevalence of pulmonary NTM colonization was 7.5% (95% CI: 7.2%–7.8%), and 75.0% (2325 of 3096) occurred in males, 16.5% (512 of 3096) in those previously treated for tuberculosis and Mycobacterium avium complex predominated (27.7% [95% CI: 27.2–28.9%]). In seven eligible studies, 27.9% (266 of 952) of participants had pulmonary NTM disease and M. kansasii with a prevalence of 69.2% [95% CI: 63.2–74.7%] was the most common cause of pulmonary NTM disease. NTM species were unidentifiable in 29.2% [2,623 of 8,980] of isolates. In conclusion, pulmonary NTM disease is a neglected and emerging public health disease and enhanced surveillance is required.

The discovery of ceftazidime/avibactam as an anti-Mycobacterium avium agent

OBJECTIVES

To determine if ceftaroline and ceftazidime combined with avibactam are efficacious against pulmonary Mycobacterium avium complex (MAC) disease.

METHODS

First, we performed a concentration-effect study of ceftaroline and ceftaroline/avibactam against extracellular MAC in test tubes. Given the difficulty of obtaining avibactam at the time of experimentation, we used a single concentration of commercial ceftazidime/avibactam, and two sets of non-treated controls, one with ceftazidime/avibactam and the other without. After finding antimicrobial activity with the ceftazidime/avibactam 'control', we performed ceftazidime/avibactam dose-effect studies in test tubes against extracellular MAC and in 24-well plates against intracellular MAC. We then performed a ceftazidime/avibactam exposure-effect and dose-fractionation studies in the hollow-fibre system model of intracellular pulmonary MAC (HFS-MAC). In each experiment, we repetitively sampled each HFS-MAC at specified times to validate ceftazidime/avibactam pharmacokinetics and to quantify bacterial burden.

RESULTS

Ceftaroline killed extracellular MAC with maximal microbial kill (Emax) of 4.87 ± 0.26 log10 cfu/mL. However, the ceftazidime/avibactam 'control' also killed MAC compared with the non-treated control. Ceftazidime/avibactam Emax was 3.8 log10 cfu/mL against extracellular bacilli and 3.6 log10 cfu/mL against intracellular MAC. In the HFS-MAC, ceftazidime/avibactam achieved a half-life of 2.5-3.3 h and killed MAC 0.61-2.40 log10 cfu/mL below the starting bacterial burden. The ceftazidime/avibactam efficacy was linked to the proportion of the dosing interval for which the concentration persists above the MIC (fT>MIC), with optimal efficacy at free-drug fT>MIC of 52% (r2 = 0.95).

CONCLUSIONS

Ceftazidime/avibactam effectively kills MAC at exposures easily achieved in the lung by clinical doses. Efficacy was higher than with clinically achievable doses of azithromycin and ethambutol.

Nontuberculous mycobacteria in Denmark, incidence and clinical importance during the last quarter-century

Disease caused by nontuberculous mycobacteria (NTM) is reported to increase due to an ageing population and a rise in the proportion of immunosuppressed patients. We did a retrospective cohort study of NTM-disease in the Danish population through a quarter-century to determine the disease burden and trends in annual incidence rates. 524,119 clinical specimens were cultured for mycobacteria from 1991 through 2015 at the International Reference Laboratory of Mycobacteriology in Denmark. Among these, 8,227 NTM strains were identified from 3,462 patients and distributed according to microbiological disease criteria. We observed no increase in NTM disease incidence or proportion of patients with positive NTM cultures during the study period (Quasi-Poisson regression, p = 0.275 and 0.352 respectively). Annual incidence rates were 1.20/10⁵ for definite NTM disease, 0.49/10⁵ for possible NTM disease and 0.88/10⁵ for NTM colonization. The incidence rate of NTM disease was highest in children aged 0-4 years (5.36/10⁵/year), predominantly with cervical Mycobacterium avium complex (MAC) adenitis. Surprisingly, based on more than half a million clinical specimens cultured for mycobacteria in Denmark through 25 years, the NTM disease burden and trend in incidence in the Danish population has not increased opposed to numerous internationals reports.

Mortality after Respiratory Isolation of Nontuberculous Mycobacteria. A Comparison of Patients Who Did and Did Not Meet Disease Criteria

RATIONALE

The mortality of patients with respiratory tract isolates of nontuberculous mycobacteria (NTM) and their risk factors for death are not well described.

OBJECTIVES

To determine age-adjusted mortality rates for patients with respiratory NTM isolates and their causes of death and to examine whether American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) diagnostic criteria identify those at higher risk of death after NTM isolation.

METHODS

We linked vital records registries with a previously identified Oregon population-based cohort of patients with NTM respiratory isolation. We excluded patients with Mycobacterium gordonae (n = 33) and those who died (n = 21) at the time of first isolation. We calculated 5-year age-adjusted mortality rates. We used Kaplan-Meier and Cox proportional hazards analysis to examine the association of ATS/IDSA criteria and other risk factors with death.

RESULTS

Of 368 subjects with respiratory NTM isolates in 2005-2006, 316 were included in the survival analysis. Most (84%) of their cultures isolated Mycobacterium avium complex. 35.1% died in the 5 years following respiratory isolation. Five-year age-adjusted mortality rates were slightly higher for those meeting (28.7/1,000) versus not meeting (23.4/1,000) ATS/IDSA criteria. In multivariate analysis, older age (adjusted hazard ratio [aHR], 1.06; 95% confidence interval [CI], 1.04-1.07) and lung cancer (aHR, 2.77; 95% CI, 1.51-5.07) were associated with an increased risk of death. A trend was noted between meeting ATS/IDSA criteria and subsequent death (aHR, 1.37; 95% CI, 0.95-1.97). Among cases, male sex, older age, and immunosuppressive therapy use were independent risk factors for death.

CONCLUSIONS

In the State of Oregon, patients with NTM respiratory isolates have high mortality, regardless of whether they meet ATS/IDSA criteria for pulmonary NTM disease. Most patients die as a result of causes other than NTM infection.

Mycobacterium avium Complex Disease

Despite the ubiqitous nature of Mycobacterium avium complex (MAC) organisms in the environment, relatively few of those who are infected develop disease. Thus, some degree of susceptibility due to either underlying lung disease or immunosuppression is required. The frequency of pulmonary MAC disease is increasing in many areas, and the exact reasons are unknown. Isolation of MAC from a respiratory specimen does not necessarily mean that treatment is required, as the decision to treatment requires the synthesis of clinical, radiographic, and microbiologic information as well as a weighing of the risks and benefits for the individual patient. Successful treatment requires a multipronged approach that includes antibiotics, aggressive pulmonary hygiene, and sometimes resection of the diseased lung. A combination of azithromycin, rifampin, and ethambutol administered three times weekly is recommend for nodular bronchiectatic disease, whereas the same regimen may be used for cavitary disease but administered daily and often with inclusion of a parenteral aminoglycoside. Disseminated MAC (DMAC) is almost exclusively seen in patients with late-stage AIDS and can be treated with a macrolide in combination with ethambutol, with or without rifabutin: the most important intervention in this setting is to gain HIV control with the use of potent antiretroviral therapy. Treatment outcomes for many patients with MAC disease remain suboptimal, so new drugs and treatment regimens are greatly needed. Given the high rate of reinfection after cure, one of the greatest needs is a better understanding of where infection occurs and how this can be prevented.

Emergence and spread of a human-transmissible multidrug-resistant nontuberculous mycobacterium

Lung infections with Mycobacterium abscessus, a species of multidrug-resistant nontuberculous mycobacteria, are emerging as an important global threat to individuals with cystic fibrosis (CF), in whom M. abscessus accelerates inflammatory lung damage, leading to increased morbidity and mortality. Previously, M. abscessus was thought to be independently acquired by susceptible individuals from the environment. However, using whole-genome analysis of a global collection of clinical isolates, we show that the majority of M. abscessus infections are acquired through transmission, potentially via fomites and aerosols, of recently emerged dominant circulating clones that have spread globally. We demonstrate that these clones are associated with worse clinical outcomes, show increased virulence in cell-based and mouse infection models, and thus represent an urgent international infection challenge.

Characteristics of Mycobacterium avium complex (MAC) pulmonary disease in previously treated lung cancer patients

Introduction

Mycobacterium avium complex (MAC) is responsible for a large portion of non-tuberculous mycobacterial (NTM) infections worldwide. Host factors such as active malignancy, immunosuppression, chronic obstructive pulmonary disease (COPD) and bronchiectasis increase the risk of MAC infection. However, the relationship between previously treated lung cancer with subsequent development of MAC pulmonary disease and treatment outcomes have not been previously studied.

Methods

We retrospectively identified all patients with lung cancer and MAC pulmonary disease documented in medical records at Mayo Clinic between January 2005 and October 2016. Patients who were diagnosed with MAC pulmonary disease before or at the time of lung cancer diagnosis were excluded. Patients meeting all inclusion criteria underwent chart review for prior oncologic treatments, clinical characteristics, and MAC treatment response.

Results

We identified 13 patients with MAC pulmonary disease and prior lung cancer, including 4 men and 9 women. Eight patients had structural lung disease that can predispose to MAC pulmonary disease, including bronchiectasis (23.0%) and COPD (46.2%). Four (30.8%) had no apparent immunosuppression or other risk factor(s) for MAC pulmonary disease. Primary pulmonary malignancies included pulmonary carcinoid, adenocarcinoma, and squamous cell carcinoma. Ten (76.9%) patients were started on antimicrobial treatment for MAC, and 8 (61.5%) patients completed MAC treatment with 6 (46.1%) patients achieving symptomatic improvement.

Conclusion

MAC pulmonary disease in previously treated lung cancer can occur without apparent risk factors for this NTM infection. Symptomatic improvement with MAC antimicrobial therapy appears to be lower than expected but comorbidities might influence outcomes in this patient population.

Development and validation of a prognostic scoring model for Mycobacterium avium complex lung disease: an observational cohort study

Background

Patients with Mycobacterium avium complex (MAC) lung disease (LD) have a heterogeneous prognosis. This study aimed to develop and validate a prognostic scoring model for these patients using independent risk factors for survival.

Methods

We retrospectively analyzed the data of patients with MAC-LD from two hospitals (cohort 1, n = 368; cohort 2, n = 118). Cohort 1 was evaluated using a multivariate Cox proportional hazards model to identify independent risk factors for overall survival (OS). A prognostic scoring model composed of these factors was developed, and cohort 1 was stratified into three groups according to risk using the log-rank test. Finally, the prognostic scoring model was validated using the data of cohort 2.

Results

Seven independent risk factors for OS were selected from cohort 1, including the male sex, age ≥ 70 years, the presence of a malignancy, body mass index <18.5 kg/m², lymphocyte count <1000 cells/μL, serum albumin levels <3.5 g/dL, and fibrocavitary disease. The areas under the receiver operating characteristic curves for the prognostic scoring model were 0.84 [95% confidence interval (CI), 0.80 − 0.89] for cohort 1 and 0.84 (95% CI, 0.75 − 0.92) for cohort 2. The 5-year OS rates of patients stratified into low-risk, intermediate-risk, and high-risk groups were 97.6, 76.6, and 30.8%, respectively (P < 0.001), in cohort 1, and 97.2, 82.3, and 45.4%, respectively (P < 0.001), in cohort 2.

Conclusions

This study is the first to develop and validate a prognostic scoring model for patients with MAC-LD. This model may prove useful in clinical settings and practical in estimating the prognosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2544-0) contains supplementary material, which is available to authorized users.

Targeting Mycolic Acid Transport by Indole-2-carboxamides for the Treatment of Mycobacterium abscessus Infections

Mycobacterium abscessus is a fast-growing, multidrug-resistant organism that has emerged as a clinically significant pathogen in cystic fibrosis (CF) patients. The intrinsic resistance of M. abscessus to most commonly available antibiotics seriously restricts chemotherapeutic options. Herein, we report the potent activity of a series of indolecarboxamides against M. abscessus. The lead compounds, 6 and 12, exhibited strong activity in vitro against a wide panel of M. abscessus isolates and in infected macrophages. High resistance levels to the indolecarboxamides appear to be associated with an A309P mutation in the mycolic acid transporter MmpL3. Biochemical analyses demonstrated that while de novo mycolic acid synthesis remained unaffected, the indolecarboxamides strongly inhibited the transport of trehalose monomycolate, resulting in the loss of trehalose dimycolate production and abrogating mycolylation of arabinogalactan. Our data introduce a hereto unexploited chemical structure class active against M. abscessus infections with promising translational development possibilities for the treatment of CF patients.

Mycobacterium llatzerense, a waterborne Mycobacterium, that resists phagocytosis by Acanthamoeba castellanii

Nontuberculous mycobacteria (NTM) are environmental bacteria increasingly associated to public health problems. In water systems, free-living amoebae (FLA) feed on bacteria by phagocytosis, but several bacteria, including many NTM, are resistant to this predation. Thus, FLA can be seen as a training ground for pathogenic bacteria. Mycobacterium llatzerense was previously described as frequently associated with FLA in a drinking water network. The present study aimed to characterize the interactions between M. llatzerense and FLA. M. llatzerense was internalised by phagocytosis and featured lipid inclusions, suggesting a subversion of host resources. Moreover, M. llatzerense survived and even multiplied in presence of A. castellanii. Using a genomic-based comparative approach, twelve genes involved in phagocytosis interference, described in M. tuberculosis, were identified in the M. llatzerense genome sequenced in this study. Transcriptomic analyses showed that ten genes were significantly upregulated during the first hours of the infection, which could partly explain M. llatzerense resistance. Additionally, M. llatzerense was shown to actively inhibit phagosome acidification. In conclusion, M. llatzerense presents a high degree of resistance to phagocytosis, likely explaining its frequent occurrence within FLA in drinking water networks. It underscores that NTM should be carefully monitored in water networks to prevent human health concerns.

Resistance to Thiacetazone Derivatives Active against Mycobacterium abscessus Involves Mutations in the MmpL5 Transcriptional Repressor MAB_4384

Available chemotherapeutic options are very limited against Mycobacterium abscessus, which imparts a particular challenge in the treatment of cystic fibrosis (CF) patients infected with this rapidly growing mycobacterium. New drugs are urgently needed against this emerging pathogen, but the discovery of active chemotypes has not been performed intensively. Interestingly, however, the repurposing of thiacetazone (TAC), a drug once used to treat tuberculosis, has increased following the deciphering of its mechanism of action and the detection of significantly more potent analogues. We therefore report studies performed on a library of 38 TAC-related derivatives previously evaluated for their antitubercular activity. Several compounds, including D6, D15, and D17, were found to exhibit potent activity in vitro against M. abscessus, Mycobacterium massiliense, and Mycobacterium bolletii clinical isolates from CF and non-CF patients. Similar to TAC in Mycobacterium tuberculosis, the three analogues act as prodrugs in M. abscessus, requiring bioactivation by the EthA enzyme, MAB_0985. Importantly, mutations in the transcriptional TetR repressor MAB_4384, with concomitant upregulation of the divergently oriented adjacent genes encoding an MmpS5/MmpL5 efflux pump system, accounted for high cross-resistance levels among all three compounds. Overall, this study uncovered a new mechanism of drug resistance in M. abscessus and demonstrated that simple structural optimization of the TAC scaffold can lead to the development of new drug candidates against M. abscessus infections.

Increasing isolation of rapidly growing mycobacteria in a low-incidence setting of environmental mycobacteria, 1994-2015

To determine trends in incidence and clinical relevance of rapidly growing mycobacteria (RGM) in a low-prevalence region of non-tuberculous mycobacteria. We retrospectively identified all patients with RGM-positive cultures between January 1994 and December 2015. Trends in incidence, clinical significance, and outcomes were assessed. One hundred and forty patients had RGM-positive cultures (116 respiratory and 24 extra-respiratory sources). The incidence of RGM isolates increased steadily from 2003 (0.34 per 100,000) to 2015 (1.73 per 100,000), with an average annual increase of 8.3%. Thirty-two patients (22.9%) had clinical disease, which trended to cluster in the second half of the study period. A positive acid-fast bacilli smear (odds ratio [OR] 97.7, 95 % CI 13.8-689.4), the presence of extra-respiratory isolates (OR 19.4, 95 % CI 5.2-72.7), and female gender (OR 5.9, 95 % CI 1.9-19.1) were independently associated with clinical disease. Cure rates were 73.3 and 87.5% for pulmonary and extra-pulmonary disease respectively. Although the burden of disease remains low, the presence of RGM isolates is increasing in our geographical setting. Whether this rise will be sustained over time and will coincide with an increase in clinical disease, or whether it is merely a cycle in the poorly understood epidemiological behaviour of environmental mycobacteria, will be seen in the near future.

Identification of nontuberculous mycobacteria using multilocous sequence analysis of 16S rRNA, hsp65, and rpoB

BACKGROUND

The isolation of nontuberculous mycobacteria (NTM) from clinical specimens has increased, and they now are considered significant opportunistic pathogens. The aims of this study were to develop a database and interpretive criteria for identifying individual species. In addition, using clinical isolates, we evaluated the clinical usefulness of 16S rRNA, hsp65, and rpoB as target genes for this method.

METHODS

The sequences of NTM for 16S rRNA, hsp65, and rpoB were collected from GenBank and checked by manual inspection. Clinical isolates collected between 2005 and 2010 were used for DNA extraction, polymerase chain reaction, and sequencing of these three genes. We constructed a database for the genes and evaluated the clinical utility of multilocus sequence analysis (MLSA) using 109 clinical isolates.

RESULTS

A total 131, 130, and 122 sequences were collected from GenBank for 16S rRNA, hsp65, and rpoB, respectively. The percent similarities of the three genes ranged from 96.57% to 100% for the 16S rRNA gene, 89.27% to 100% for hsp65, and 92.71% to 100% for rpoB. When we compared the sequences of 109 clinical strains with those of the database, the rates of species-level identification were 71.3%, 86.79%, and 81.55% with 16S rRNA, hsp65, and rpoB, respectively. We could identify 97.25% of the isolates to the species level when we used MLSA.

CONCLUSION

There were significant differences among the utilities of the three genes for species identification. The MLSA technique would be helpful for identification of NTM.

Combinations of avibactam and carbapenems exhibit enhanced potencies against drug-resistant Mycobacterium abscessus

AIM

The objective of this study was to assess if avibactam, a new β-lactamase inhibitor, can restore the potency of carbapenems, a sub-class of β-lactams, against Mycobacterium abscessus clinical isolates.

MATERIALS & METHODS

28 M. abscessus clinical isolates that are resistant to multiple drugs currently used to treat its infection were included. MIC of carbapenems alone and in combination with avibactam against these strains were determined.

RESULTS

Tebipenem, an oral carbapenem, and ertapenem and panipenem exhibited the greatest shift in MIC when supplemented with avibactam.

CONCLUSION

Avibactam restores MICs of tebipenem, ertapenem and panipenem against M. abscessus to therapeutically achievable concentrations and raises the possibility of usefulness of these carbapenems to treat drug-resistant M. abscessus infections.

Clinical Impact and Cost-effectiveness of Xpert MTB/RIF Testing in Hospitalized Patients With Presumptive Pulmonary Tuberculosis in the United States

Background

Microscopic examination of acid-fast-stained sputum smears is the current standard of care in the United States to determine airborne infection isolation (AII) of inpatients with presumptive pulmonary tuberculosis (PTB). However, nucleic acid amplification testing (NAAT) with the Xpert MTB/RIF assay (Xpert) may be more efficient and less costly.

Methods

This prospective observational cohort study enrolled a consecutive sample of 318 AII-eligible inpatients from a public hospital in Seattle, Washington, from March 2012 to October 2013. Sputum samples were collected from each inpatient and analyzed using smear microscopy, culture, drug susceptibility testing, and NAAT. The performance, clinical utility (AII duration and survival), and cost-effectiveness from an institutional perspective were compared for 5 testing strategies.

Results

Among the 318 admissions with presumptive PTB, 20 (6.3%) were culture-positive for Mycobacterium tuberculosis. The sensitivity of 1 Xpert, 2 Xperts, 2 smears, or 3 smears compared to culture was 0.85 (95% confidence interval [CI], .61–.96), 0.95 (95% CI, .73–1.0), 0.70 (95% CI, .46–.88), and 0.80 (95% CI, .56–.93), respectively. A cost-effectiveness analysis of the study results demonstrated that an Xpert test on 1 unconcentrated sputum sample (assuming equivalent results for unconcentrated and concentrated sputum samples) is the most cost-effective strategy (99.9% preferred at willingness-to-pay of US$50000) and on average would save 51.5 patient-hours in AII and up to $11466 relative to microscopy without a compromise in sensitivity.

Conclusions

In hospitalized patients with presumptive PTB in a low-burden setting, NAAT can reduce AII and is comparably sensitive, more specific, and more cost-effective than smear microscopy.

Dose response models and a quantitative microbial risk assessment framework for the Mycobacterium avium complex that account for recent developments in molecular biology, taxonomy, and epidemiology

Mycobacterium avium complex (MAC) is a group of environmentally-transmitted pathogens of great public health importance. This group is known to be harbored, amplified, and selected for more human-virulent characteristics by amoeba species in aquatic biofilms. However, a quantitative microbial risk assessment (QMRA) has not been performed due to the lack of dose response models resulting from significant heterogeneity within even a single species or subspecies of MAC, as well as the range of human susceptibilities to mycobacterial disease. The primary human-relevant species and subspecies responsible for the majority of the human disease burden and present in drinking water, biofilms, and soil are M. avium subsp. hominissuis, M. intracellulare, and M. chimaera. A critical review of the published literature identified important health endpoints, exposure routes, and susceptible populations for MAC risk assessment. In addition, data sets for quantitative dose-response functions were extracted from published in vivo animal dosing experiments. As a result, seven new exponential dose response models for human-relevant species of MAC with endpoints of lung lesions, death, disseminated infection, liver infection, and lymph node lesions are proposed. Although current physical and biochemical tests used in clinical settings do not differentiate between M. avium and M. intracellulare, differentiating between environmental species and subspecies of the MAC can aid in the assessment of health risks and control of MAC sources. A framework is proposed for incorporating the proposed dose response models into susceptible population- and exposure route-specific QMRA models.

Mortality among patients with pulmonary non-tuberculous mycobacteria disease

SETTING

Tertiary referral center, National Institutes of Health (NIH), USA.

OBJECTIVE

To estimate the mortality rate and its correlates among persons with pulmonary non-tuberculous mycobacteria (PNTM) disease.

DESIGN

A retrospective review of 106 patients who were treated at the NIH Clinical Center and met American Thoracic Society/Infectious Diseases Society of America criteria for PNTM. Eligible patients were aged ⩾18 years and did not have cystic fibrosis or human immunodeficiency virus (HIV) infection.

RESULTS

Of 106 patients followed for a median of 4.9 years, 27 (25%) died during follow-up, for a mortality rate of 4.2 per 100 person-years. The population was predominantly female (88%) and White (88%), with infrequent comorbidities. Fibrocavitary disease (adjusted hazard ratio [aHR] 3.3, 95% confidence interval [CI] 1.3-8.3) and pulmonary hypertension (aHR 2.1, 95%CI 0.9-5.1) were associated with a significantly elevated risk of mortality in survival analysis.

CONCLUSIONS

PNTM remains a serious public health concern, with a consistently elevated mortality rate across multiple populations. Significant risk factors for death include fibrocavitary disease and pulmonary hypertension. Further research is needed to more specifically identify clinical and microbiologic factors that jointly influence disease outcome.

Comparative genome analyses of Mycobacterium avium reveal genomic features of its subspecies and strains that cause progression of pulmonary disease

Pulmonary disease caused by nontuberculous mycobacteria (NTM) is increasing worldwide. Mycobacterium avium is the most clinically significant NTM species in humans and animals, and comprises four subspecies: M. avium subsp. avium (MAA), M. avium subsp. silvaticum (MAS), M. avium subsp. paratuberculosis (MAP), and M. avium subsp. hominissuis (MAH). To improve our understanding of the genetic landscape and diversity of M. avium and its role in disease, we performed a comparative genome analysis of 79 M. avium strains. Our analysis demonstrated that MAH is an open pan-genome species. Phylogenetic analysis based on single nucleotide variants showed that MAH had the highest degree of sequence variability among the subspecies, and MAH strains isolated in Japan and those isolated abroad possessed distinct phylogenetic features. Furthermore, MAP strains, MAS and MAA strains isolated from birds, and many MAH strains that cause the progression of pulmonary disease were grouped in each specific cluster. Comparative genome analysis revealed the presence of genetic elements specific to each lineage, which are thought to be acquired via horizontal gene transfer during the evolutionary process, and identified potential genetic determinants accounting for the pathogenic and host range characteristics of M. avium.

Spectrum and Clinical Course of Visual Field Abnormalities in Ethambutol Toxicity

Visual toxicities from ethambutol are rare but represent one of the few causes of non-glaucomatous and non-compressive bitemporal hemianopsia. The authors present a six-patient case series illustrating variable clinical presentation and reversibility of visual loss in patients treated with ethambutol for Mycobacterium avium complex, including four patients who presented with visual field defects suggestive of bitemporal hemianopsia. Two additional patients were being followed for glaucoma, developed visual field defects with ethambutol treatment, and subsequently recovered with cessation of drug. In patients being treated with ethambutol, reversible bitemporal hemianopsia was the most commonly noted presentation of ethambutol toxicity.

Understanding nontuberculous mycobacterial lung disease: it's been a long time coming

With a surprising predictability, most studies and reviews addressing therapy for nontuberculous mycobacterial (NTM) lung disease either start or end by mentioning the paucity of data from randomized and controlled trials. That is a legitimate criticism for NTM lung disease therapy, but it also somehow seems to influence attitudes toward all aspects of NTM investigation. Certainly the study of NTM diseases in general and NTM lung disease in particular is a recent development. Previously, NTM were viewed as minor, if inconvenient, pathogens similar to Mycobacterium tuberculosis. However, over the last three decades, NTM have emerged as increasingly important pathogens that are clearly different compared with tuberculosis. Although there has been frustratingly slow progress in the treatment of NTM diseases, in contrast there has unquestionably been impressive progress in almost every other realm of investigation into NTM disease. Our understanding of NTM lung disease a) pathophysiology, including mechanisms of organism acquisition, b) epidemiology, including estimates of disease prevalence, c) mycobacteriology, including application of molecular laboratory techniques and matrix-assisted laser desorption ionization–time of flight (MALDI–TOF) mass spectrometry, and d) even treatment strategies, including the recognition of innate drug resistance mechanisms, has immeasurably and permanently changed and advanced the landscape for NTM lung disease. It is no longer necessary to apologize for the state of NTM lung disease knowledge and understanding, but rather it is time to recognize the great distance we have travelled over the last 30 years.

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.

Treatment of Mycobacterium abscessus Infection

Mycobacterium abscessus is often resistant to multiple antimicrobial drugs, and data supporting effective drugs or dosing regimens are limited. To better identify treatment approaches and associated toxicities, we collected a series of case reports from the Emerging Infections Network. Side effects were common and often led to changing or discontinuing therapy.