Mycobacterial lung disease in cystic fibrosis: a prospective study

Nontuberculous Mycobacterial Infections in Cystic Fibrosis

Nontuberculous mycobacteria (NTM) are important pathogens, with a longitudinal prevalence of up to 20% within the cystic fibrosis (CF) population. Diagnosis of NTM pulmonary disease in people with CF (pwCF) is challenging, as a majority have NTM infection that is transient or indolent, without evidence of clinical consequence. In addition, the radiographic and clinical manifestations of chronic coinfections with typical CF pathogens can overlap those of NTM, making diagnosis difficult. Comprehensive care of pwCF must be optimized to assess the true clinical impact of NTM and to improve response to treatment. Treatment requires prolonged, multidrug therapy that varies depending on NTM species, resistance pattern, and extent of disease. With a widespread use of highly effective modulator therapy (HEMT), clinical signs and symptoms of NTM disease may be less apparent, and sensitivity of sputum cultures further reduced. The development of a disease-specific approach to the diagnosis and treatment of NTM infection in pwCF is a research priority, as a lifelong strategy is needed for this high-risk population.

High Prevalence of Nontuberculous Mycobacteria in Cystic Fibrosis Patients in Tropical French Reunion Island

BACKGROUND

Reunion Island is a French overseas department located in a tropical area, where cystic fibrosis incidence is high. Cystic fibrosis (CF) patients are at risk of developing nontuberculous mycobacteria (NTM) infection. Epidemiologic studies are lacking in Reunion Island.

METHODS

From 2002 to 2015, a retrospective review was performed in university hospitals on Reunion Island. All CF patients having at least 1 positive NTM isolate were included. Clinical, radiologic, and microbiologic data were collected from patient records.

RESULTS

Fifty-one CF patients were included. The overall estimated prevalence of NTM was 26.4% in total CF population and 36.9% in patients over 12 years of age. Mycobacterium abscessus and Mycobacterium avium were the most frequently identified species found in 31 patients (60.8%) and 14 patients (27.4%), respectively. A rare NTM species: Mycobacterium simiae was found in 4 patients (7.8%). Twenty-nine patients (56.9%) met the American Thoracic Society (ATS) criteria for infection. They were more likely younger with a low body mass index and more frequently infected by Mycobacterium abscessus (22/29).

CONCLUSION

The overall prevalence of NTM in tropical Reunion Island is 3 times higher than in metropolitan France. A different environmental exposure in a tropical climate or risk factors related to cystic fibrosis or its treatment in Reunion patients could explain it.

General Overview of Nontuberculous Mycobacteria Opportunistic Pathogens: Mycobacterium avium and Mycobacterium abscessus

Nontuberculous mycobacteria (NTM) are emerging human pathogens, causing a wide range of clinical diseases affecting individuals who are immunocompromised and who have underlying health conditions. NTM are ubiquitous in the environment, with certain species causing opportunistic infection in humans, including Mycobacterium avium and Mycobacterium abscessus. The incidence and prevalence of NTM infections are rising globally, especially in developed countries with declining incidence rates of M. tuberculosis infection. Mycobacterium avium, a slow-growing mycobacterium, is associated with Mycobacterium avium complex (MAC) infections that can cause chronic pulmonary disease, disseminated disease, as well as lymphadenitis. M. abscessus infections are considered one of the most antibiotic-resistant mycobacteria and are associated with pulmonary disease, especially cystic fibrosis, as well as contaminated traumatic skin wounds, postsurgical soft tissue infections, and healthcare-associated infections (HAI). Clinical manifestations of diseases depend on the interaction of the host's immune response and the specific mycobacterial species. This review will give a general overview of the general characteristics, vulnerable populations most at risk, pathogenesis, treatment, and prevention for infections caused by Mycobacterium avium, in the context of MAC, and M. abscessus.

Antibiotic treatment for nontuberculous mycobacteria lung infection in people with cystic fibrosis

BACKGROUND

Nontuberculous mycobacteria are mycobacteria, other than those in the Mycobacterium tuberculosis complex, and are commonly found in the environment. Nontuberculous mycobacteria species (most commonly Mycobacterium avium complex and Mycobacterium abscessus) are isolated from the respiratory tract of approximately 5% to 40% of individuals with cystic fibrosis; they can cause lung disease in people with cystic fibrosis leading to more a rapid decline in lung function and even death in certain circumstances. Although there are guidelines for the antimicrobial treatment of nontuberculous mycobacteria lung disease, these recommendations are not specific for people with cystic fibrosis and it is not clear which antibiotic regimen may be the most effective in the treatment of these individuals. This is an update of a previous review.

OBJECTIVES

The objective of our review was to compare antibiotic treatment to no antibiotic treatment, or to compare different combinations of antibiotic treatment, for nontuberculous mycobacteria lung infections in people with cystic fibrosis. The primary objective was to assess the effect of treatment on lung function and pulmonary exacerbations and to quantify adverse events. The secondary objectives were to assess treatment effects on the amount of bacteria in the sputum, quality of life, mortality, nutritional parameters, hospitalizations and use of oral antibiotics.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and hand searching of journals and conference abstract books. Date of last search: 24 February 2020. We also searched a register of ongoing trials and the reference lists of relevant articles and reviews. Date of last search: 21 March 2019.

SELECTION CRITERIA

Any randomized controlled trials comparing nontuberculous mycobacteria antibiotics to no antibiotic treatment, as well as one nontuberculous mycobacteria antibiotic regimen compared to another nontuberculous mycobacteria antibiotic regimen, in individuals with cystic fibrosis.   DATA COLLECTION AND ANALYSIS: Data were not collected because in the one trial identified by the search, data specific to individuals with cystic fibrosis could not be obtained from the pharmaceutical company.

MAIN RESULTS

One completed trial was identified by the searches, but data specific to individuals with cystic fibrosis could not be obtained from the pharmaceutical company.

AUTHORS' CONCLUSIONS

This review did not find any evidence for the effectiveness of different antimicrobial treatment for nontuberculous mycobacteria lung disease in people with cystic fibrosis. Until such evidence becomes available, it is reasonable for clinicians to follow published clinical practice guidelines for the diagnosis and treatment of nodular or bronchiectatic pulmonary disease due to Mycobacterium avium complex or Mycobacterium abscessus in patients with cystic fibrosis.

Disease caused by non-tuberculous mycobacteria in children with cystic fibrosis

Non-tuberculous mycobacterial (NTM) (especially M. abscessus complex) infections pose a considerable challenge in the management of lung disease in patients with cystic fibrosis (CF). The apparent increase in prevalence is likely multifactorial. Emergent evidence of patient-to-patient transmission and isolation of highly resistant strains is a concern for all CF centers around the world. Treatment is often long and burdensome with multiple agents. Treatment side effects are frequent and can cause significant morbidity. Although consensus guidelines provide some direction, many units are faced with the challenges of: finding drug combinations for highly resistant strains; dealing with interruptions of treatment; discussing additional facilitating procedures in the form of gastrostomy and long-term vascular access devices; as well as supporting families emotionally and psychologically through the process.

Nontuberculous Mycobacterial Infections in Cystic Fibrosis

Nontuberculous mycobacteria (NTM) are important emerging cystic fibrosis (CF) pathogens, with estimates of prevalence ranging from 6% to 13%. Diagnosis of NTM disease in patients with CF is challenging, as the infection may remain indolent in some, without evidence of clinical consequence, whereas other patients suffer significant morbidity and mortality. Treatment requires prolonged periods of multiple drugs and varies depending on NTM species, resistance pattern, and extent of disease. The development of a disease-specific approach to the diagnosis and treatment of NTM infection in CF patients is a research priority, as a lifelong strategy is needed for this high-risk population.

Nontuberculous mycobacteria in cystic fibrosis: Updates and the path forward

Nontuberculous mycobacteria (NTM) are troublesome pathogens that can cause significant pulmonary disease in patients with cystic fibrosis (CF). Diagnosis can be difficult in the setting of underlying CF and treatment regimens are burdensome on both patients and providers. Recent consensus guidelines for treatment of NTM in CF have provided a guide for the CF community, however research is lagging regarding accuracy of our diagnostic abilities and treatment efficacy. In this review, we provide new insights into the complexity of NTM from emerging whole genome sequencing data, a summary of current NTM diagnosis and treatment guidelines, highlight new treatment options, and discuss future research projects which aim to better define which patients to treat and timing and duration of treatment.

Rapidly Growing Mycobacteria

Rapidly growing mycobacteria (RGM) compose approximately one-half of the currently validated mycobacterial species and are divided into six major groups, including the Mycobacterium fortuitum group, M. chelonae/M. abscessus complex, M. smegmatis group, M. mucogenicum group, M. mageritense / M. wolinskyi , and the pigmented RGM. This review discusses each group and highlights the major types of infections associated with each group. Additionally, phenotypic and molecular laboratory identification methods, including gene sequencing, mass spectrometry, and the newly emerging whole-genome sequencing, are detailed, along with a discussion of the current antimicrobial susceptibility methods and patterns of the most common pathogenic species.

Antibiotic treatment for nontuberculous mycobacteria lung infection in people with cystic fibrosis

BACKGROUND

Nontuberculous mycobacteria are mycobacteria, other than those in the Mycobacterium tuberculosis complex, and are commonly found in the environment. Nontuberculous mycobacteria species (most commonly Mycobacterium avium complex and Mycobacterium abscessus) are isolated from the respiratory tract of approximately 5% to 40% of individuals with cystic fibrosis; they can cause lung disease in people with cystic fibrosis leading to more a rapid decline in lung function and even death in certain circumstances. Although there are guidelines for the antimicrobial treatment of nontuberculous mycobacteria lung disease, these recommendations are not specific for people with cystic fibrosis and it is not clear which antibiotic regimen may be the most effective in the treatment of these individuals. This is an update of a previous review.

OBJECTIVES

The objective of our review was to compare antibiotic treatment to no antibiotic treatment, or to compare different combinations of antibiotic treatment, for nontuberculous mycobacteria lung infections in people with cystic fibrosis. The primary objective was to assess the effect of treatment on lung function and pulmonary exacerbations and to quantify adverse events. The secondary objectives were to assess treatment effects on the amount of bacteria in the sputum, quality of life, mortality, nutritional parameters, hospitalizations and use of oral antibiotics.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and hand searching of journals and conference abstract books. Date of last search: 02 September 2016.We also searched a register of ongoing trials and the reference lists of relevant articles and reviews. Date of last search: 03 November 2016.

SELECTION CRITERIA

Any randomized controlled trials comparing nontuberculous mycobacteria antibiotics to no antibiotic treatment, as well as one nontuberculous mycobacteria antibiotic regimen compared to another nontuberculous mycobacteria antibiotic regimen, in individuals with cystic fibrosis.   DATA COLLECTION AND ANALYSIS: Data were not collected because in the one trial identified by the search, data specific to individuals with cystic fibrosis could not be obtained from the pharmaceutical company.

MAIN RESULTS

One completed trial was identified by the searches, but data specific to individuals with cystic fibrosis could not be obtained from the pharmaceutical company.

AUTHORS' CONCLUSIONS

This review did not find any evidence for the effectiveness of different antimicrobial treatment for nontuberculous mycobacteria lung disease in people with cystic fibrosis. Until such evidence becomes available, it is reasonable for clinicians to follow published clinical practice guidelines for the diagnosis and treatment of nodular or bronchiectatic pulmonary disease due to Mycobacterium avium complex or Mycobacterium abscessus in patients with cystic fibrosis.

Nontuberculous Mycobacteria in Cystic Fibrosis

Nontuberculous mycobacteria (NTM) are found in approximately 10 % of cystic fibrosis (CF) patients, but only a portion will develop NTM disease. The management of CF lung disease should be optimized, including antibiotic therapy targeted to the individual's usual airway bacteria, prior to considering treatment for NTM lung disease. Those who meet criteria for NTM lung disease may not necessarily require treatment and could be monitored expectantly if symptoms and radiographic findings are minimal. However, the presence of Mycobacterium abscessus complex (MABSC), severe lung disease, and/or anticipated lung transplant should prompt NTM therapy initiation. For CF patients with Mycobacterium avium complex (MAC), recommended treatment includes triple antibiotic therapy with a macrolide, rifampin, and ethambutol. Azithromycin is generally our preferred macrolide in CF as it is better tolerated and has fewer drug-drug interactions. MABSC treatment is more complex and requires an induction phase (oral macrolide and two IV agents including amikacin) as well as a maintenance phase (nebulized amikacin and two to three oral antibiotics including a macrolide). The induction phase may range from one to three months (depending on infection severity, treatment response, and medication tolerability). For both MAC and MABSC, treatment duration is extended 1-year post-culture conversion. However, in patients who do not achieve culture negative status but tolerate therapy, we consider ongoing treatment for mycobacterial suppression and prevention of disease progression.

Diagnosis of Adult Patients with Cystic Fibrosis

The diagnosis of cystic fibrosis (CF) is being made with increasing frequency in adults. Patients with CF diagnosed in adulthood typically present with respiratory complaints, and often have recurrent or chronic airway infection. At the time of initial presentation individuals may appear to have clinical manifestation limited to a single organ, but with subclinical involvement of the respiratory tract. Adult-diagnosed patients have a good response to CF center care, and newly available cystic fibrosis transmembrane receptor-modulating therapies are promising for the treatment of residual function mutation, thus increasing the importance of the diagnosis in adults with unexplained bronchiectasis.

Nontuberculous Mycobacterial Infections in Cystic Fibrosis

Nontuberculous mycobacteria (NTM) are important emerging cystic fibrosis (CF) pathogens, with estimates of prevalence ranging from 6% to 13%. Diagnosis of NTM disease in patients with CF is challenging, as the infection may remain indolent in some, without evidence of clinical consequence, whereas other patients suffer significant morbidity and mortality. Treatment requires prolonged periods of multiple drugs and varies depending on NTM species, resistance pattern, and extent of disease. The development of a disease-specific approach to the diagnosis and treatment of NTM infection in CF patients is a research priority, as a lifelong strategy is needed for this high-risk population.

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.

Antibiotic treatment for nontuberculous mycobacteria lung infection in people with cystic fibrosis

BACKGROUND

Nontuberculous mycobacteria are mycobacteria, other than those in the Mycobacterium tuberculosis complex, and are commonly found in the environment. Nontuberculous mycobacteria species (most commonly Mycobacterium avium complex and Mycobacterium abscessus) are isolated from the respiratory tract of approximately 5% to 20% of individuals with cystic fibrosis; they can cause lung disease in people with cystic fibrosis leading to more a rapid decline in lung function and even death in certain circumstances. Although there are guidelines for the antimicrobial treatment of nontuberculous mycobacteria lung disease, these recommendations are not specific for people with cystic fibrosis and it is not clear which antibiotic regimen may be the most effective in the treatment of these patients.

OBJECTIVES

The objective of our review was to compare antibiotic treatment to no antibiotic treatment, or to compare different combinations of antibiotic treatment, for nontuberculous mycobacteria lung infections in people with cystic fibrosis. The primary objective was to assess the effect of treatment on lung function and pulmonary exacerbations and to quantify adverse events. The secondary objectives were to assess treatment effects on the amount of bacteria in the sputum, quality of life, mortality, nutritional parameters, hospitalizations and use of oral antibiotics.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and hand searching of journals and conference abstract books. Date of last search: 13 November 2014.We also searched a register of ongoing trials and the reference lists of relevant articles and reviews. Date of last search: 24 September 2014.

SELECTION CRITERIA

Any randomized controlled trials comparing nontuberculous mycobacteria antibiotics to no antibiotic treatment, as well as one nontuberculous mycobacteria antibiotic regimen compared to another nontuberculous mycobacteria antibiotic regimen, in individuals with cystic fibrosis.  

DATA COLLECTION AND ANALYSIS

Data were not collected because no completed trials were identified by the searches.

MAIN RESULTS

No completed trials were identified by the searches, but one ongoing trial was identified, which may be eligible for inclusion in this review when completed.

AUTHORS' CONCLUSIONS

This review did not find any evidence for the effectiveness of different antimicrobial treatment for nontuberculous mycobacteria lung disease in people with cystic fibrosis. Until such evidence becomes available, it is reasonable for clinicians to follow the American Thoracic Society guidelines for the diagnosis and treatment of nodular or bronchiectatic pulmonary disease due to Mycobacterium avium complex or Mycobacterium abscessus in patients with cystic fibrosis.

Clinical significance of a first positive nontuberculous mycobacteria culture in cystic fibrosis

RATIONALE

Little is known about outcomes of infection with nontuberculous mycobacteria (NTM) in cystic fibrosis (CF) or about the significance of a positive NTM culture. Determining which patients are at risk for active NTM disease is clinically valuable.

OBJECTIVES

To examine the clinical course of subjects with CF with an initial positive NTM culture and identify characteristics associated with active NTM disease.

METHODS

We performed a retrospective study of pediatric and adult subjects with CF with at least one positive NTM culture at the Colorado CF Center from 2000 to 2010.

MEASUREMENTS AND MAIN RESULTS

Mycobacterium avium complex was the first identified NTM in the majority of subjects (73%). The frequency of growing a second NTM species was 26% at 5 years. Clinical characteristics and distribution of NTM species between pediatric and adult subjects were similar except for differences in baseline FEV1 (89% vs. 71%; P < 0.001) and coinfection with Pseudomonas aeruginosa (33% vs. 55%; P = 0.04). Over 60% of subjects had transient or persistent infection but not active NTM disease. Subjects who developed active NTM disease were distinguished from those with transient or persistent infection, respectively, by FEV1 at the time of first positive NTM culture (72% vs. 84 or 86%; P = 0.02) and FEV1 decline in the prior year (-5.8%/yr vs. -0.7%/yr [P = 0.009] or -0.4%/yr [P = 0.001]).

CONCLUSIONS

The majority of patients with CF with a first positive NTM culture do not progress to active disease. Lower lung function and accelerated lung function decline appear to be indicators of the significance of an initial positive NTM culture.

Nontuberculous mycobacteria: the changing epidemiology and treatment challenges in cystic fibrosis

PURPOSE OF REVIEW

Although patients with cystic fibrosis (CF) face numerous infectious pathogens over the course of their lifespan, increasing attention has recently been paid to nontuberculous mycobacteria (NTM). As reported prevalence rates rise across many countries such as the United States, the ability to recognize disease caused by NTM and subsequently treat such disease has become increasingly important. This review summarizes new observations on the epidemiology of NTM in CF as well as key elements to consider during the treatment phase.

RECENT FINDINGS

Although overall rates of NTM isolation appear to be increasing, particular concern has focused on the emerging predominance of Mycobacterium abscessus. New data suggest that chronic macrolide therapy now part of routine CF care has contributed to this rise; however, these have yet to be confirmed prospectively. Transmission of M. abscessus between CF patients has also now been described through the use of genome sequencing. Although the greater virulence of M. abscessus makes it a challenging species to treat, identification of the subspecies type can now determine the presence of inducible macrolide resistance, thereby helping to guide treatment.

SUMMARY

Given increasing prevalence rates, clinicians should maintain a high level of suspicion for NTM as disease-causing organisms in CF, particularly for M. abscessus. New knowledge regarding this species, however, can help to tailor appropriate therapy.

Shifting paradigms of nontuberculous mycobacteria in cystic fibrosis

Important paradigms of pulmonary disease with nontuberculous mycobacteria (NTM) are currently shifting based on an increasing attention within the field of cystic fibrosis (CF). These shifts are likely to benefit the management of all patients with pulmonary NTM, regardless of underlying pathology. Currently several key areas are being revised: The first outbreak of human NTM transmission has been proven and new evidence of biofilm growth in vivo has been demonstrated. A better understanding of the clinical impact of NTM infection has led to increased diagnostic vigilance and new recommendations for lung transplantation are under way. While recent changes have reinvigorated the interest in NTM disease, the challenge remains, whether such advances can be successfully translated into improved management and care.

Mycobacterium abscessus induces a limited pattern of neutrophil activation that promotes pathogen survival

Mycobacterium abscessus is a rapidly growing mycobacterium increasingly detected in the neutrophil-rich environment of inflamed tissues, including the cystic fibrosis airway. Studies of the immune reaction to M. abscessus have focused primarily on macrophages and epithelial cells, but little is known regarding the neutrophil response despite the predominantly neutrophillic inflammation typical of these infections. In the current study, human neutrophils released less superoxide anion in response to M. abscessus than to Staphylococcus aureus, a pathogen that shares common sites of infection. Exposure to M. abscessus induced neutrophil-specific chemokine and proinflammatory cytokine genes. Although secretion of these protein products was confirmed, the quantity of cytokines released, and both the number and level of gene induction, was reduced compared to S. aureus. Neutrophils mediated killing of M. abscessus, but phagocytosis was reduced when compared to S. aureus, and extracellular DNA was detected in response to both bacteria, consistent with extracellular trap formation. In addition, M. abscessus did not alter cell death compared to unstimulated cells, while S. aureus enhanced necrosis and inhibited apoptosis. However, neutrophils augment M. abscessus biofilm formation. The response of neutrophils to M. abscessus suggests that the mycobacterium exploits neutrophil-rich settings to promote its survival and that the overall neutrophil response was reduced compared to S. aureus. These studies add to our understanding of M. abscessus virulence and suggest potential targets of therapy.

Antibiotic treatment for nontuberculous mycobacteria lung infection in people with cystic fibrosis

BACKGROUND

Nontuberculous mycobacteria are mycobacteria, other than those in the Mycobacterium tuberculosis complex, and are commonly found in the environment. Nontuberculous mycobacteria species (most commonly Mycobacterium avium complex and Mycobacterium abscessus) are isolated from the respiratory tract of approximately 5% to 20% of individuals with cystic fibrosis; they can cause lung disease in people with cystic fibrosis leading to more a rapid decline in lung function and even death in certain circumstances. Although there are guidelines for the antimicrobial treatment of nontuberculous mycobacteria lung disease, these recommendations are not specific for people with cystic fibrosis and it is not clear which antibiotic regimen may be the most effective in the treatment of these patients.

OBJECTIVES

The objective of our review was to compare antibiotic treatment to no antibiotic treatment, or to compare different combinations of antibiotic treatment, for nontuberculous mycobacteria lung infections in people with cystic fibrosis. The primary objective was to assess the effect of treatment on lung function and pulmonary exacerbations and to quantify adverse events. The secondary objectives were to assess treatment effects on the amount of bacteria in the sputum, quality of life, mortality, nutritional parameters, hospitalizations and use of oral antibiotics.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and hand searching of journals and conference abstract books. Date of last search: 19 July 2012.We also searched a register of ongoing trials and the reference lists of relevant articles and reviews. Date of last search: 10 August 2012.

SELECTION CRITERIA

Any randomized controlled trials comparing nontuberculous mycobacteria antibiotics to no antibiotic treatment, as well as one nontuberculous mycobacteria antibiotic regimen compared to another nontuberculous mycobacteria antibiotic regimen, in individuals with cystic fibrosis.  

DATA COLLECTION AND ANALYSIS

Data were not collected because no completed trials were identified by the searches.

MAIN RESULTS

No completed trials were identified by the searches, but one ongoing trial was identified, which may be eligible for inclusion in this review when completed.

AUTHORS' CONCLUSIONS

This review did not find any evidence for the effectiveness of different antimicrobial treatment for nontuberculous mycobacteria lung disease in people with cystic fibrosis. Until such evidence becomes available, it is reasonable for clinicians to follow the American Thoracic Society guidelines for the diagnosis and treatment of nodular or bronchiectatic pulmonary disease due to Mycobacterium avium complex or Mycobacterium abscessus in patients with cystic fibrosis.

Nontuberculous Mycobacterial Pulmonary Infection in Patients with Cystic Fibrosis

The prevalence of nontuberculous mycobacteria (NTM) recovered from patients with cystic fibrosis (CF) appears to be increasing, probably related to improved surveillance and microbiological procedures and an increase in the life expectancy of patients with CF. The distinction between active lung infection and colonization is often difficult to assess in patients with CF because of the marked overlap in the clinical and radiological presentation of CF lung disease and lung disease caused by NTM infection. The possibility of active NTM lung infection should be considered in those patients with compatible radiographic changes and/or progressive deterioration in lung function who do not improve with specific antibiotic therapy and who have repeatedly positive sputum cultures and smears for NTM. Patients with repeatedly positive results of acid-fast smears are more likely to be infected than colonized. Pseudomonas overgrowth may confuse the results of sputum and bronchoalveolar lavage fluid cultures. Decontamination of respiratory samples from patients with CF with 5% oxalic acid results in improved bacteriological recovery of NTM. Skin tests are of limited value as a screening tool for NTM. Since the course of NTM lung infection is often slow, careful follow-up with repeated sputum cultures, chest radiographs and computed tomography (CT) scans may be needed. Treatment of NTM lung disease in patients with CF presents great difficulties because of abnormal gastrointestinal drug absorption and pharmacokinetics in this patient population. Treatment varies according to the mycobacterial species isolated. Long-term multidrug regimens including rifampin (rifampicin) and ethambutol are usually required. Monitoring serum drug levels is a useful indicator of correct dosage in order to prevent adverse effects due to potential drug interactions and altered pharmacokinetics in patients with CF.

Antimicrobial susceptibility testing, drug resistance mechanisms, and therapy of infections with nontuberculous mycobacteria

Within the past 10 years, treatment and diagnostic guidelines for nontuberculous mycobacteria have been recommended by the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA). Moreover, the Clinical and Laboratory Standards Institute (CLSI) has published and recently (in 2011) updated recommendations including suggested antimicrobial and susceptibility breakpoints. The CLSI has also recommended the broth microdilution method as the gold standard for laboratories performing antimicrobial susceptibility testing of nontuberculous mycobacteria. This article reviews the laboratory, diagnostic, and treatment guidelines together with established and probable drug resistance mechanisms of the nontuberculous mycobacteria.

Mycobacterium abscessus glycopeptidolipid prevents respiratory epithelial TLR2 signaling as measured by HβD2 gene expression and IL-8 release

Mycobacterium abscessus has emerged as an important cause of lung infection, particularly in patients with bronchiectasis. Innate immune responses must be highly effective at preventing infection with M. abscessus because it is a ubiquitous environmental saprophyte and normal hosts are not commonly infected. M. abscessus exists as either a glycopeptidolipid (GPL) expressing variant (smooth phenotype) in which GPL masks underlying bioactive cell wall lipids, or as a variant lacking GPL which is immunostimulatory and invasive in macrophage infection models. Respiratory epithelium has been increasingly recognized as playing an important role in the innate immune response to pulmonary pathogens. Respiratory epithelial cells express toll-like receptors (TLRs) which mediate the innate immune response to pulmonary pathogens. Both interleukin-8 (IL-8) and human β-defensin 2 (HβD2) are expressed by respiratory epithelial cells in response to toll-like receptor 2 (TLR2) receptor stimulation. In this study, we demonstrate that respiratory epithelial cells respond to M. abscessus variants lacking GPL with expression of IL-8 and HβD2. Furthermore, we demonstrate that this interaction is mediated through TLR2. Conversely, M. abscessus expressing GPL does not stimulate expression of IL-8 or HβD2 by respiratory epithelial cells which is consistent with "masking" of underlying bioactive cell wall lipids by GPL. Because GPL-expressing smooth variants are the predominant phenotype existing in the environment, this provides an explanation whereby initial M. abscessus colonization of abnormal lung airways escapes detection by the innate immune system.

Deletion of the mmpL4b gene in the Mycobacterium abscessus glycopeptidolipid biosynthetic pathway results in loss of surface colonization capability, but enhanced ability to replicate in human macrophages and stimulate their innate immune response

Mycobacterium abscessus is considered to be the most virulent of the rapidly growing mycobacteria. Generation of bacterial gene knockout mutants has been a useful tool for studying factors that contribute to virulence of pathogenic bacteria. Until recently, the optimal genetic approach to generation of M. abscessus gene knockout mutants was not clear. Based on the recent identification of genetic recombineering as the preferred approach, a M. abscessus mutant was generated in which the gene mmpL4b, critical to glycopeptidolipid synthesis, was deleted. Compared to the previously well-characterized parental strain 390S, the mmpL4B deletion mutant had lost sliding motility and the ability to form biofilm, but acquired the ability to replicate in human macrophages and stimulate macrophage Toll-like receptor 2. This study demonstrates that deletion of a gene associated with expression of a cell-wall lipid can result in acquisition of an immunostimulatory, invasive bacterial phenotype and has important implications for the study of M. abscessus pathogenesis at the cellular level.

Clinical significance of microbial infection and adaptation in cystic fibrosis

A select group of microorganisms inhabit the airways of individuals with cystic fibrosis. Once established within the pulmonary environment in these patients, many of these microbes adapt by altering aspects of their structure and physiology. Some of these microbes and adaptations are associated with more rapid deterioration in lung function and overall clinical status, whereas others appear to have little effect. Here we review current evidence supporting or refuting a role for the different microbes and their adaptations in contributing to poor clinical outcomes in cystic fibrosis.

The changing microbial epidemiology in cystic fibrosis

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Non-tuberculous mycobacteria in children with cystic fibrosis: isolation, prevalence, and predictors

BACKGROUND

Screening for non-tuberculous mycobacteria (NTM) is recommended for adults with cystic fibrosis (CF). The relevance of this organism in North American pediatric CF patients is unclear as there is limited NTM prevalence data for children. We aimed to determine the prevalence of NTM in children with CF from a single expectorated sputum and identify clinical predictors of NTM isolation. Additionally, we compared two different sputum decontamination methods before mycobacterial culture.

METHODS

From March to November 2004, all sputum-producing patients aged 6-18 years attending the CF clinic at the Hospital for Sick Children in Toronto, Canada, were screened for NTM. Sputum samples were processed by both a single (N-acetyl-l-cysteine + NaOH) and double (N-acetyl-l-cysteine + NaOH + oxalic Acid) decontamination method. Using our CF clinic database and patient charts we analyzed differences in FEV(1), age, sex, pancreatic sufficiency, body mass index, bacterial colonization, and antibiotic use between NTM positive and negative patients.

RESULTS

Of 98 study patients, 6 (6.1%) were positive for NTM, 2 with Mycobacterium abscessus, and 4 with Mycobacterium avium complex. One patient with M. abscessus had clinically significant lung disease requiring treatment. We found no predictors of NTM isolation. The double decontamination method allowed detection of only half (3/6) of the positive NTM cultures.

CONCLUSIONS

As the NTM prevalence rate in children with CF is within the range previously reported in adults and there are no reliable clinical predictors for isolation, annual sputum screening is needed to identify NTM in children. Further research is needed to determine the best sputum decontamination method for NTM culture in pediatric patients.

Multicenter study of prevalence of nontuberculous mycobacteria in patients with cystic fibrosis in france

We performed a multicenter prevalence study of nontuberculous mycobacteria (NTM) involving 1,582 patients (mean age, 18.9 years; male/female ratio, 1.06) with cystic fibrosis in France. The overall NTM prevalence (percentage of patients with at least one positive culture) was 6.6% (104/1,582 patients), with prevalences ranging from 3.7% (in the east of France) to 9.6% (in the greater Paris area). Mycobacterium abscessus complex (MABSC; 50 patients) and Mycobacterium avium complex (MAC; 23 patients) species were the most common NTM, and the only ones associated with fulfillment of the American Thoracic Society bacteriological criteria for NTM lung disease. The "new" species, Mycobacterium bolletii and Mycobacterium massiliense, accounted for 40% of MABSC isolates. MABSC species were isolated at all ages, with a prevalence peak between 11 and 15 years of age (5.8%), while MAC species reached their highest prevalence value among patients over 25 years of age (2.2%).

The antioxidant mimetic, MnTE-2-PyP, reduces intracellular growth of Mycobacterium abscessus

Mycobacterium abscessus is a rapidly growing environmental mycobacterium that can cause severe skin, soft tissue, and lung infections. M. abscessus grows inside macrophages, and these cells release a vast number of proinflammatory cytokines in response to infections. The metalloporphyrin, MnTE-2-PyP, is a broad antioxidant that reduces inflammatory cell signaling. Macrophage-like THP-1 cells were infected with M. abscessus in the presence or absence of MnTE-2-PyP. MnTE-2-PyP significantly decreased, in a dose-dependent manner, the number of M. abscessus organisms recovered from infected THP-1 cells 4 and 8 days after infection. Furthermore, when combined with clarithromycin, MnTE-2-PyP additively reduced the number of cells associated with M. abscessus. A mechanism of bacterial growth inhibition by MnTE-2-PyP was then elucidated. It was found that MnTE-2-PyP promoted the survival of infected THP-1 cells and increased fusion of M. abscessus-containing phagosomes with lysosomes.

Acute respiratory failure involving an R variant of Mycobacterium abscessus

We report the case of a cystic fibrosis patient colonized with a smooth-morphotype form of Mycobacterium abscessus who developed acute respiratory failure with the emergence of an isogenic rough (R) variant while he was recovering from peritonitis-induced shock. This report emphasizes the role of R forms in severe M. abscessus infections.

Multicenter cross-sectional study of nontuberculous mycobacterial infections among cystic fibrosis patients, Israel

This 2-year cross-sectional evaluation of nontuberculous mycobacterial (NTM) infections involved all Israeli medical centers that treat cystic fibrosis patients. The study comprised 186 patients whose sputum was analyzed for NTM. The prevalence of NTM isolates was 22.6%, and 6.5% and 10.8% of the patients fulfilled the 1997 and 2007 American Thoracic Society criteria for NTM lung disease, respectively. Mycobacterium simiae (40.5%), M. abscessus (31.0%), and M. avium complex (14.3%) were the most prevalent. Presence of Aspergillus spp. in sputum and the number of sputum specimens processed for mycobacteria were the most significant predictors for isolation of NTM (odds ratio [OR] = 5.14, 95% confidence interval [CI] 1.87-14.11 and OR = 1.47, 95% CI 1.17-1.85, respectively). The incidence of NTM pulmonary infections is increasing among cystic fibrosis patients, reflecting the increase in longevity of such patients as well as environmental exposure to various species of mycobacteria.

Differential antibiotic susceptibility of Mycobacterium abscessus variants in biofilms and macrophages compared to that of planktonic bacteria

Mycobacterium abscessus causes refractory pulmonary infections requiring surgery for cure. It exists as a smooth biofilm-forming phenotype which is noninvasive and a rough, non-biofilm-forming phenotype which can invade macrophages and cause persistent pulmonary infection in mice. We have postulated that the dissociation of the smooth phenotype to the rough phenotype may lead to invasive lung disease following initial colonization of the airways. Amikacin, cefoxitin, and clarithromycin are standard therapies for this infection. We determined the MICs of these antibiotics against this pathogen in biofilms and macrophages, the niches that it likely occupies in the human host. Our results demonstrate that even though the MICs indicate sensitivity to these antibiotics, the minimal bactericidal concentrations for amikacin and clarithromycin were substantially higher and were out of the range of the concentrations achievable in serum. Cefoxitin demonstrated only bacteriostatic activity. In addition, although amikacin had modest activity against M. abscessus in biofilms, clarithromycin demonstrated only minimal activity at the highest concentrations tested. Our results indicate that M. abscessus in mature biofilms is in a stationary-phase state and that clarithromycin is relatively inactive against stationary-phase M. abscessus. In human macrophages, all three antibiotics were only bacteriostatic for M. abscessus variants at 10 times their MICs. These results suggest why treatment failure with antibiotics alone is common in the clinical setting of M. abscessus pulmonary infection. Determination of the efficacies of new antibiotics should include an assessment of their activities against the smooth and rough M. abscessus morphotypes in biofilms and macrophages.

Atypical mycobacterial infection in patients with cystic fibrosis: update on clinical microbiology methods

While patients with cystic fibrosis (CF) have had dramatic improvement in their survival rates, this has been accompanied by the emergence of more virulent pathogens such as Pseudomonas aeruginosa and Burkholderia cepacia complex organisms. In addition, there has been emergence of organisms of increasing clinical significance such as the nontuberculous mycobacterial (NTM). Although TB infection in patients with CF is extremely uncommon, there is growing concern with regard to atypical Mycobacterium spp, in particular Mycobacterium abscessus. Many methods of decontamination of sputum, which have been adapted from TB methodologies, are ineffective; as shown by the overgrowth of P. aeruginosa, it is essential that decontamination methods are optimized to overcome this. Establishing optimal methods of isolation and determining accurate levels of prevalence is of importance as, although NTM may be isolated relatively infrequently in CF populations, their clinical status in pulmonary disease is now beginning to emerge.

Spontaneous reversion of Mycobacterium abscessus from a smooth to a rough morphotype is associated with reduced expression of glycopeptidolipid and reacquisition of an invasive phenotype

Mycobacterium abscessus is an increasingly important cause of human disease; however, virulence determinants are largely uncharacterized. Previously, it was demonstrated that a rough, wild-type human clinical isolate (390R) causes persistent, invasive infection, while a smooth isogenic mutant (390S) has lost this capability. During serial passage of 390S, a spontaneous rough revertant was obtained, which was named 390V. This revertant regained the ability to cause persistent, invasive infection in human monocytes and the lungs of mice. Glycopeptidolipid (GPL), which plays a role in environmental colonization, was present in abundance in the cell wall of 390S, and was associated with sliding motility and biofilm formation. In contrast, a marked reduction in the amount of GPL in the cell wall of 390R and 390V was correlated with cord formation, a property associated with mycobacterial virulence. These results indicate that the ability to switch between smooth and rough morphologies may allow M. abscessus to transition between a colonizing phenotype and a more virulent, invasive form.

Mycobacterium abscessus: an emerging rapid-growing potential pathogen. Review article

Mycobacterium abscessus is the most pathogenic and chemotherapy-resistant rapid-growing mycobacterium. It is commonly associated with contaminated traumatic skin wounds and with post-surgical soft tissue infections. It is also one of the mycobacteria that are most often isolated from cystic fibrosis patients. It is essential to differentiate this species from the formerly indistinct "M. chelonae-complex", as chemotherapy is especially difficult in M. abscessussenso strictu. Clarithromycin or azithromycin are the only regular oral antimycobacterial agents with an effect on M. abscessus, and should preferably be supplemented with other drugs since long-term monotherapy may cause resistance. Amikacin is a major parenteral drug against M. abscessus that should also be given in combination with another drug. The recently introduced drug tigecycline may prove to be an important addition to chemotherapy, but has yet to be fully clinically evaluated as an antimycobacterial agent. Surgery can be curative, or at least helpful, in the healing of M. abscessus infection, and if conducted, it should include the removal of all foreign or necrotic material. There is increasing awareness of M. abscessus as an emerging pathogen.

Clinical, microbiological, and epidemiological findings of an outbreak of Mycobacterium abscessus hand-and-foot disease

In 2003, we identified an outbreak of clinically distinct lesions involving the hands and feet associated with a public wading pool in Edmonton, Alberta, Canada. A total of 85 cases were identified. The management and follow-up of 41 children and 1 adult patients is presented. Skin lesions occurred within a median incubation period of 29 days and approximately 88 days for the adult patient. Lesions resolved within a median of 58 days and approximately 150 days for the adult patient. Patients were treated with clarithromycin, topical antibiotic dressings, and/or incision and drainage of pustules or followed without treatment. All resolved without complication. The pool was closed and cleaned. The M. abscessus hand-and-foot disease is characterized by the onset, mainly in children, of tender, erythematous papules, pustules, and abscesses with a self-limited course. This is the first documented M. abscessus outbreak associated with wading pool exposure.

Manifestations of cystic fibrosis diagnosed in adulthood

PURPOSE OF REVIEW

This review highlights the phenotypic features that lead to the diagnosis of cystic fibrosis in adults, and the prognosis of these patients.

RECENT FINDINGS

With the widespread availability of genetic testing and a greater appreciation of the clinical spectrum of the disease, the diagnosis of cystic fibrosis is being made with increasing frequency in adults. Clinical features that lead to the diagnosis include respiratory symptoms and chronic airway infection with typical cystic fibrosis pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus, as well as nontuberculous mycobacteria. Often these patients have previously received diagnoses of asthma, chronic bronchitis, or emphysema. Pancreatic insufficiency is much less common in the adult receiving the diagnosis, but pancreatitis occurs with greater frequency. Occasionally, individuals receive diagnoses of apparent single-organ manifestations such as idiopathic pancreatitis or congenital bilateral absence of the vas deferens, but with negligible involvement of the respiratory tract. On rare occasions, patients receiving the diagnosis as adults can present with classic features of the disease. Although lung disease is generally less severe in cystic fibrosis patients receiving the diagnosis as adults than in adult patients who received the diagnosis as infants, the extent of bronchiectasis can nonetheless be severe. The clinical course of patients receiving a diagnosis of cystic fibrosis in adulthood is largely unknown, but frequently they have milder disease and a more favorable prognosis.

SUMMARY

Clinicians must be aware of the potential for adults with chronic respiratory tract infections, unexplained bronchiectasis, congenital bilateral absence of the vas deferens, or pancreatitis to have cystic fibrosis despite the age at presentation.

Mycobacterium chelonae in a CF patient with anaplastic large cell lymphoma

A 13-year-old patient with cystic fibrosis was diagnosed with anaplastic large cell lymphoma. At the same time colonization with Mycobacterium chelonae was detected in sputum cultures. Despite massive immunosuppression, the patient did not show evidence of mycobacterial invasive disease. Colonisation persisted for 18 months after discontinuation of chemotherapy and was not detected in the 6 years thereafter. This case highlights the dilemma of differentiating between colonisation and infection if mycobacteria are found in CF sputum samples.

[Nontuberculous mycobacteria in patients with cystic fibrosis]

OBJECTIVE

Patients with cystic fibrosis are at great risk of infection by nontuberculous mycobacteria from the environment because of certain predisposing factors such as bronchiectasis, malnutrition, and diabetes. The aim of this study was to analyze the mycobacterial content of sputum smears and cultures from adult patients with cystic fibrosis attended at a specialized unit for adults from March 1997 through December 2001.

PATIENTS AND METHODS

Sputum samples were collected prospectively according to a protocol applied at each visit, and during most exacerbations staining and culture for mycobacteria were ordered in addition to the usual cultures for bacteria and fungi. A tuberculin test was performed at the end of the study.

RESULTS

Twenty-eight patients (16 men) with cystic fibrosis were enrolled. The mean (SD) age was 25.3 (6.7) years. A total of 251 samples were cultured (range in number of samples per patient, 1-31). The mean period of follow up was 40.3 (22.1) months. The sputum smear was positive in 29 cases (4 patients); the culture was positive in 7 patients. More than 3 samples were positive in only 4 patients. Mycobacterium abscessus was isolated in 3 cases, Mycobacterium avium complex in 2 and Mycobacterium simiae in 1 and other an unidentified rapid growth Mycobacterium species. The Mantoux test was positive in 5 patients. Two of the 4 patients in whose samples mycobacteria were isolated repeatedly required treatment.

CONCLUSIONS

The prevalence of nontuberculous mycobacterial infection is high in patients with cystic fibrosis. Staining and culture for mycobacteria should be carried out regularly and whenever exacerbation of pulmonary symptoms cannot be attributed to bacteria usually found in such patients. Patients with recurrent isolations of mycobacteria should be monitored closely.

Age-related prevalence and distribution of nontuberculous mycobacterial species among patients with cystic fibrosis

We studied the prevalence and species distribution of nontuberculous mycobacteria (NTM) in relation to age in 385 patients with cystic fibrosis (CF) (mean age +/- standard deviation [range], 12.0 +/- 6.1 [1 to 24] years; sex ratio, 0.53) attending three Parisian centers. The overall prevalence of NTM in sputum was 8.1% (31 out of 385). The following NTM were isolated (n = 33): Mycobacterium abscessus (n = 13, 39.4%), Mycobacterium avium complex (MAC) (n = 7, 21.2%), Mycobacterium gordonae (n = 6, 18.2%), and other (n = 7, 21.2%). Sixteen patients met the American Thoracic Society microbiological criteria for NTM infection, including 11 patients positive for M. abscessus, 4 for MAC, and 1 for MAC and Mycobacterium kansasii. The overall prevalence of NTM was significantly lower in patients under 15 years old than for patients equal to or more than 15 years old (4.8 versus 14.9%, respectively; P = 0.001). M. abscessus was isolated at all ages, while MAC was not recovered before 15 years (prevalence of 0.0 and 5.2% in patients aged 1 to 14 and 15 to 24, respectively; P = 0.001).

Intra- and interpatient variability of the hsp65 and 16S-23S intergenic gene region in Mycobacterium abscessus strains from patients with cystic fibrosis

To establish the exact pathogenic role of Mycobacterium abscessus in cystic fibrosis (CF), molecular tests are required for accurate identification. Forty-eight M. abscessus isolates from seven patients with CF were analyzed by sequence analysis for sequence variants within the hsp65 gene and the 16S-23S intergenic sequence (ITS). We detected two different hsp65 genes and correspondingly two ITS sequevars belonging to M. abscessus type I and type II.