Non-tuberculous mycobacteria in end stage cystic fibrosis: implications for lung transplantation

[Indications and contraindications to lung transplant: patient selection]

Lung transplant (LT) is a valid treatment for patients with end-stage lung disease such as cystic fibrosis, emphysema, pulmonary fibrosis and pulmonary arterial hypertension (85% of indications) and for selected candidates. The "good recipient" was introduced early to a specialised center, has had complete pre-LT assessment and complete information. At the end of this assessment, the absolute contraindications were eliminated (cardiovascular pathologies, recent neoplasia, active viral diseases, severe psychiatric disorders), advanced age risks were discussed, co-morbidities to treat were listed and an individualised therapeutic pre-LT program has been decided (based on exercise and muscle rehabilitation, nutritional support, anti-infectious treatments, active management of co-morbidities such as diabetes, hypertension, gastro-esophageal reflux…) with a psychological follow-up if necessary. Timely inscription on waiting list must be decided, early enough to avoid extreme handicap or risk pre-LT death, but not too early to have a survival benefit linked to LT. Death without LT prognosis criteria are still studied, and even if they do not fully define the risk of death of an individualised patient, they are taken into account by the recommendations of the societies; since 2006, LT indications are based on severity criteria of the selected patient, defined for each recipient diagnosis. LT aims to improve survival and quality of life of the patient, and this is especially true when the patient is referred, prepared and monitored early enough by the transplant team; the aim is to limit the risk of death before LT (before listing and on waiting list) and early post-LT morbimortality.

[Medical complications of lung transplantation]

In 2010, lung transplantation is a valuable therapeutic option for a number of patients suffering from of end-stage non-neoplastic pulmonary diseases. The patients frequently regain a very good quality of life, however, long-term survival is often hampered by the development of complications such as the bronchiolitis obliterans syndrome, metabolic and infectious complications. As the bronchiolitis obliterans syndrome is the first cause of death in the medium and long term, an intense immunosuppressive treatment is maintained for life in order to prevent or stabilize this complication. The immunosuppression on the other hand induces a number of potentially severe complications including metabolic complications, infections and malignancies. The most frequent metabolic complications are arterial hypertension, chronic renal insufficiency, diabetes, hyperlipidemia and osteoporosis. Bacterial, viral and fungal infections are the second cause of mortality. They are to be considered as medical emergencies and require urgent assessment and targeted therapy after microbiologic specimens have been obtained. They should not, under any circumstances, be treated empirically and it has also to be kept in mind that the lung transplant recipient may present several concomitant infections. The most frequent malignancies are skin cancers, the post-transplant lymphoproliferative disorders, Kaposi's sarcoma and some types of bronchogenic carcinomas, head/neck and digestive cancers. Lung transplantation is no longer an exceptional procedure; thus, the pulmonologist will be confronted with such patients and should be able to recognize the symptoms and signs of the principal non-surgical complications. The goal of this review is to give a general overview of the most frequently encountered complications. Their assessment and treatment, though, will most often require the input of other specialists and a multidisciplinary and transversal approach.

Mycobacterium abscessus: a new player in the mycobacterial field

Mycobacterium abscessus, a relative of Koch's bacillus (the bacterium that causes tuberculosis), has recently emerged as the cause of an increasing number of both community- and hospital-acquired infections in humans; it also constitutes a serious threat for cystic fibrosis patients. This situation is worsened by its exceptionally high natural and acquired antibiotic resistance that complicates treatment. Although a rapid grower, it shares some traits with Koch's bacillus, including the ability to induce a persistent lung disease associated with caseous lesions, a landmark of Mycobacterium tuberculosis infection. Its genome sequence and microarrays are now available, and efficient genetic tools have recently been developed. Here we consider the various advantages of using this species as an experimental model to study tuberculosis and other related mycobacterial diseases.

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.

Non mycobacterial virulence genes in the genome of the emerging pathogen Mycobacterium abscessus

Mycobacterium abscessus is an emerging rapidly growing mycobacterium (RGM) causing a pseudotuberculous lung disease to which patients with cystic fibrosis (CF) are particularly susceptible. We report here its complete genome sequence. The genome of M. abscessus (CIP 104536T) consists of a 5,067,172-bp circular chromosome including 4920 predicted coding sequences (CDS), an 81-kb full-length prophage and 5 IS elements, and a 23-kb mercury resistance plasmid almost identical to pMM23 from Mycobacterium marinum. The chromosome encodes many virulence proteins and virulence protein families absent or present in only small numbers in the model RGM species Mycobacterium smegmatis. Many of these proteins are encoded by genes belonging to a “mycobacterial” gene pool (e.g. PE and PPE proteins, MCE and YrbE proteins, lipoprotein LpqH precursors). However, many others (e.g. phospholipase C, MgtC, MsrA, ABC Fe(3+) transporter) appear to have been horizontally acquired from distantly related environmental bacteria with a high G+C content, mostly actinobacteria (e.g. Rhodococcus sp., Streptomyces sp.) and pseudomonads. We also identified several metabolic regions acquired from actinobacteria and pseudomonads (relating to phenazine biosynthesis, homogentisate catabolism, phenylacetic acid degradation, DNA degradation) not present in the M. smegmatis genome. Many of the “non mycobacterial” factors detected in M. abscessus are also present in two of the pathogens most frequently isolated from CF patients, Pseudomonas aeruginosa and Burkholderia cepacia. This study elucidates the genetic basis of the unique pathogenicity of M. abscessus among RGM, and raises the question of similar mechanisms of pathogenicity shared by unrelated organisms in CF patients.

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.

Nontuberculous mycobacterial pulmonary disease

PURPOSE OF REVIEW

Pulmonary disease caused by nontuberculous mycobacteria is occurring with greater frequency, and previously unrecognized manifestations of nontuberculous mycobacteria are being identified. Paralleling this increase, improvements in laboratory techniques now allow for more precise identification of nontuberculous mycobacteria and recognition of new species. Consequently, clinicians are more often confronted with diagnostic and therapeutic challenges relevant to the care of patients with nontuberculous mycobacterial lung disease.

RECENT FINDINGS

In response to this burgeoning clinical need, the American Thoracic Society and Infectious Disease Society of America jointly published an updated consensus statement on nontuberculous mycobacterial pulmonary disease in 2007. This document, in conjunction with original investigations in the field, has advanced our understanding of the pathogenesis of nontuberculous mycobacterial lung disease, its clinical manifestations, and the efficacy of medical and surgical therapy.

SUMMARY

The present article will review our current understanding of nontuberculous mycobacterial pulmonary disease with particular emphasis on pathogenesis, diagnosis, and therapeutic decision making. Areas of clinical controversy in which current data are inadequate to guide our decision making will be highlighted.

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.

Successful recovery after disseminated infection due to mycobacterium abscessus in a lung transplant patient: subcutaneous nodule as first manifestation--a case report

Mycobacterium abscessus infection following lung transplantation (LT) has been described in a few cases. It is characterized by a variable initial location and subsequent course in this special risk group of patients, particularly those with cystic fibrosis (CF). Herein we have presented the case of a patient subjected to LT due to CF, who 1 year after transplantation developed a subcutaneous nodule produced by M abscessus, with subsequent hematogenous spread as well as bronchial and bone marrow involvement. Antecedents prior to LT included Staphylococcus aureus colonization and sputum positivity for Aspergillus fumigatus and Scedosporium apioespermum. Treatment with ciprofloxacin and linezolid was started on the basis of the antibiogram findings. The latter antibiotic was replaced by clarithromycin for 6 months. Two years later, the patient remains asymptomatic with respiratory function parameters in the normal range. The infected patient described herein was our only case with sepsis and multisystemic spread. The important mortality among such cases reported in the literature makes early diagnosis and treatment essential.

Lung transplantation for cystic fibrosis: Current concepts and one center's experience

BACKGROUND

Although new approaches to the treatment of patients with cystic fibrosis (CF) are significantly prolonging their lives, most patients will eventually develop respiratory failure due to progressive bronchiectasis caused by chronic lung infection and inflammation and die from to respiratory failure. We examined our center's (University of Wisconsin Hospital and Clinics) experience with lung transplantation for patients with CF and reviewed the literature to examine current and evolving approaches to transplantation for this indication.

METHODS

We reviewed all published literature pertaining to lung transplantation for CF through 2006, and we reviewed all aspects of transplantation for patients with CF at our institution from 1994 to 2005.

RESULTS

Major complications following lung transplantation include acute rejection, bacterial infection, and bronchiolitis obliterans. Five-year survival at UWHC (Kaplan-Meier) is 67%, and survival was not adversely affected by transplanting patients receiving mechanical ventilation. The major cause of death for transplant recipients was bronchiolitis obliterans syndrome (BOS).

CONCLUSIONS

Lung transplantation for CF is associated with acceptable survival rates and can improve quality of life. Lung transplant should be offered to all patients with advanced CF lung disease if they meet currently accepted inclusion and exclusion criteria.