Nontuberculous mycobacteria. II: nested-cohort study of impact on cystic fibrosis lung disease

Infections in chronic lung diseases

Chronic lung diseases are prevalent worldwide and cause significant mortality and suffering. This article discusses infections that occur in three chronic lung diseases: chronic obstructive pulmonary disease, bronchiectasis, and cystic fibrosis. Rather than discussing the role of infections as etiology of these diseases, this article focuses on infections that occur in the background of established chronic lung disease.

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.

First isolations of Segniliparus rugosus from patients with cystic fibrosis

We report three cases of the new genus Segniliparus isolated from patients with cystic fibrosis. All isolates were unambiguously identified by 16S rRNA gene sequencing as Segniliparus rugosus (GenBank accession no. AY 60892). Drug susceptibility results that may enhance treatment for cystic fibrosis patients with this opportunistic pathogen are presented.

Cystic fibrosis: a review of epidemiology and pathobiology

Improvements in outcomes for patients who have cystic fibrosis (CF) have been striking in the last 30 years. Median survival now approaches the fifth decade of life. Advances in the understanding of the basic defect and the pathobiology of CF have led to new treatments, some of which have undoubtedly contributed to this success. Improved understanding of the basic defect and the acquisition and maintenance of epidemiologic resources for the CF population in the United States have allowed us to determine predictors of survival and identify genetic, environmental, and therapeutic factors that may influence it. This article reviews some of the key epidemiologic and pathobiologic factors discovered thus far.

Infection Control Practice in Cystic Fibrosis Centers

In this article, the authors outline some of the major historical events that signaled the need to better understand mechanisms of infection in cystic fibrosis (CF). The authors discuss general principles of infection control, focusing on issues of particular importance to patients who have CF. The authors also describe the major pathogens associated with the CF airway, provide a review of findings from inpatient and outpatient studies of infection control, and provide an outline of future directions for investigation.

Special considerations for patients with cystic fibrosis undergoing lung transplantation

This article reviews lung transplantation in patients with cystic fibrosis (CF). Lung transplantation is commonly utilized for patients with end-stage CF. There are several characteristics of CF that present unique challenges before and after lung transplantation. There is new information available that can be utilized to predict outcomes in patients with end-stage CF, and therefore can help in decisions of referral and listing for lung transplantation. The new lung allocation score, which allocates organs to patients who are on the lung transplant waiting list in the United States, presents new challenges and opportunities for patients with end-stage CF. In addition, the effect of the presence of microbiological flora prior to lung transplantation has been better linked to outcomes after lung transplantation. It is now known that, other than those patients harboring Burkholderia cepacia in their lungs before transplantation, most CF patients can undergo transplantation successfully. Nutrition remains an important issue among CF patients, and diabetes is a common problem after lung transplantation. In contrast, liver disease does not usually present major problems but, if it is severe, can necessitate liver and lung transplantation. Mechanical ventilation prior to transplantation might not be an absolute contraindication for CF patients. CF lung transplant recipients have good outcomes after lung transplantation compared with those of other lung transplant recipients. Quality of life is dramatically improved. However, they are still prone to common complications that all lung transplant recipients are prone to, including primary graft dysfunction, acute and chronic rejection, a variety of infections and malignancies, and renal failure.

Molecular epidemiology of Mycobacterium abscessus, with focus on cystic fibrosis

Mycobacterium abscessus has been isolated increasingly often from the respiratory tracts of cystic fibrosis (CF) patients. It is not known whether these organisms are transmitted from person to person or acquired from environmental sources. Here, colony morphology and pulsed-field gel electrophoresis (PFGE) pattern were examined for 71 isolates of M. abscessus derived from 14 CF patients, three non-CF patients with chronic respiratory M. abscessus infection or colonization, one patient with mastoiditis, and four patients with infected wounds, as well as for six isolates identified as environmental contaminants in various clinical specimens. Contaminants and wound isolates mainly exhibited smooth colony morphology, while a rough colony phenotype was significantly associated with chronic airway colonization (P=0.014). Rough strains may exhibit increased airway-colonizing capacity, the cause of which remains to be determined. Examination by PFGE of consecutive isolates from the same patient showed that they all represented a single strain, even in cases where both smooth and rough isolates were present. When PFGE patterns were compared, it was shown that 24 patients had unique strains, while four patients harbored strains indistinguishable by PFGE. Two of these were siblings with CF. The other two patients, one of whom had CF, had not had contact with each other or with the siblings. Our results show that most patients colonized by M. abscessus in the airways have unique strains, indicating that these strains derive from the environment and that patient-to-patient transmission rarely occurs.

Multidrug-resistant organisms in cystic fibrosis: management and infection-control issues

Chronic infection and inflammation are the hallmarks of cystic fibrosis lung disease. As cystic fibrosis patients are living longer owing to more intense treatment, multidrug-resistant organisms are being isolated increasingly from patients' respiratory tracts. While the adverse effects of Pseudomonas aeruginosa and Burkholderia cepacia complex are well described, less is known about the clinical significance of other emerging multidrug-resistant organisms, such as methicillin-resistant Staphylococcus aureus and Stenotrophomonas maltophilia. Owing to multiple mechanisms of antimicrobial resistance, these organisms are difficult to treat and often require combination antibiotic therapy. Until more is known about their pathogenicity and effect on clinical outcomes, physicians should be aware of the potential transmissibility of these organisms and implement adequate infection control strategies.

Prospective analysis of cystic fibrosis transmembrane regulator mutations in adults with bronchiectasis or pulmonary nontuberculous mycobacterial infection

BACKGROUND

Bronchiectasis and pulmonary infection with nontuberculous mycobacteria (NTM) may be associated with disease-causing mutations in the cystic fibrosis transmembrane regulator (CFTR).

METHODS

Fifty adult patients at Stanford University Medical Center with a diagnosis of bronchiectasis and/or pulmonary NTM infection were prospectively characterized by sweat chloride measurement, comprehensive mutational analysis of CFTR, and sputum culture results.

RESULTS

A de novo diagnosis of cystic fibrosis (CF) was established in 10 patients (20%). Patients with CF were more likely than those without CF to have mucus plugging seen on chest high-resolution CT, and women with a CF diagnosis were thinner, with a significantly lower mean body mass index than the non-CF subjects. Thirty CFTR mutations were identified in 24 patients (50% prevalence). Sweat chloride concentration was elevated > 60 mEq/dL (diagnostic of CF) in seven patients (14%), and from 40 to 60 mEq/dL in eight patients (16%). The frequency of CFTR mutations was elevated above that expected in the general population: heterozygous DeltaF508 (12% vs 3%), R75Q (14% vs 1%), and intron 8 5T (17% vs 5 to 10%). Other known CFTR mutations identified were V456A, G542X, R668C, I1027T, D1152, R1162L, W1282X, and L183I. Three novel CFTR mutations were identified: A394V, F650L, and C1344S.

CONCLUSIONS

Mutations in CFTR that alter RNA splicing and/or functional chloride conductance are common in this population, and are likely to contribute to the susceptibility and pathogenesis of adult bronchiectasis and pulmonary NTM infection. Careful clinical evaluation for disease cause should be undertaken in this clinical context.

The Expanding Spectrum of Mycobacterium avium Complex-Associated Pulmonary Disease

Nontuberculous mycobacteria (NTM) are increasingly recognized as important pulmonary pathogens. Mycobacterium avium intracellulare complex (MAC) causes most lung infections due to NTM. Patients with preexisting lung disease or immunodeficiency are at greatest risk for developing MAC infection. The majority of MAC pulmonary cases, however, occur in immunocompetent elderly women in association with nodular infiltrates and bronchiectasis. More recently, pulmonary disease has also been described in immunocompetent patients after exposure to MAC-contaminated hot tubs. We describe a case of aggressive MAC lung disease in a young immunocompetent female patient without preexisting lung disease whose clinical and pathologic characteristics do not fit into any of these categories and may represent a unique manifestation of MAC lung disease.

Survival of environmental mycobacteria in Acanthamoeba polyphaga

Free-living amoebae in water are hosts to many bacterial species living in such an environment. Such an association enables bacteria to select virulence factors and survive in adverse conditions. Waterborne mycobacteria (WBM) are important sources of community- and hospital-acquired outbreaks of nontuberculosis mycobacterial infections. However, the interactions between WBM and free-living amoebae in water have been demonstrated for only few Mycobacterium spp. We investigated the ability of a number (n = 26) of Mycobacterium spp. to survive in the trophozoites and cysts of Acanthamoeba polyphaga. All the species tested entered the trophozoites of A. polyphaga and survived at this location over a period of 5 days. Moreover, all Mycobacterium spp. survived inside cysts for a period of 15 days. Intracellular Mycobacterium spp. within amoeba cysts survived when exposed to free chlorine (15 mg/liter) for 24 h. These data document the interactions between free-living amoebae and the majority of waterborne Mycobacterium spp. Further studies are required to examine the effects of various germicidal agents on the survival of WBM in an aquatic environment.

Mycobacterium abscessus chest wall and pulmonary infection in a cystic fibrosis lung transplant recipient

Mycobacterial infections are increasingly recognized in cystic fibrosis (CF) patients before transplant; however, knowledge about the clinical significance or spectrum of infections observed with mycobacterial infections in lung transplant recipients is still evolving. Herein, we report a case of infection with Mycobacterium abscessus in a CF lung transplant recipient. Despite aggressive treatment before and peri-operatively with anti-mycobacterial therapy, the patient developed skin and soft tissue infection of the incision and of bilateral breast implants, eventually leading to disseminated pulmonary infection and death. This report highlights the potential for M abscessus to cause post-transplant disease in CF patients undergoing lung transplant, despite peri-operative anti-mycobacterial therapy. Thus, pre-transplant colonization with M abscessus should be viewed as a strong relative, if not absolute, contraindication to lung transplantation. The combination of the virulent pre-transplant pathogen M abscessus and foreign bodies in the chest likely acted synergistically to contribute to the unfortunate outcome in this patient.

Lung Disease Due to the More Common Nontuberculous Mycobacteria

As the prevalence of tuberculosis (TB) declines in the developed world, the proportion of mycobacterial lung disease due to nontuberculous mycobacteria (NTM) is increasing. It is not clear whether there is a real increase in prevalence or whether NTM disease is being recognized more often because of the introduction of more sensitive laboratory techniques, and that more specimens are being submitted for mycobacterial staining and culture as the result of a greater understanding of the role of NTM in conditions such as cystic fibrosis, posttransplantation and other forms of iatrogenic immunosuppression, immune reconstitution inflammatory syndrome, fibronodular bronchiectasis, and hypersensitivity pneumonitis. The introduction of BACTEC liquid culture systems (BD; Franklin Lakes, NJ) and the development of nucleic acid amplification and DNA probes allow more rapid diagnosis of mycobacterial disease and the quicker differentiation of NTM from TB isolates. High-performance liquid chromatography, polymerase chain reaction, and restriction fragment length polymorphism analysis have helped to identify new NTM species. Although treatment regimens that include the newer macrolides are more effective than the earlier regimens, failure rates are still too high and relapse may occur after apparently successful therapy. Moreover, treatment regimens are difficult to adhere to because of their long duration, adverse effects, and interactions with the other medications that these patients require. The purpose of this article is to review the common presentations of NTM lung disease, the conditions associated with NTM lung disease, and the clinical features and treatment of the NTM that most commonly cause lung disease.

Is limited computed tomography the future for imaging the lungs of children with cystic fibrosis?

Perspective on the paper by Jiménez et al (see page 388)

Outcomes of Adults with Cystic Fibrosis Infected with Antibiotic-Resistant Pseudomonas aeruginosa

BACKGROUND

Although Pseudomonas aeruginosa is the most common bacterial infection in adults with cystic fibrosis and frequently develops resistance to multiple classes of antibiotics, it has not been determined whether patients with multiple antibiotic-resistant Pseudomonas aeruginosa have worse clinical outcomes than patients with more susceptible strains.

OBJECTIVES

This study assessed the impact of multiply-resistant P. aeruginosa on lung function, hospitalizations, antibiotic use, lung transplantation and survival in adults with cystic fibrosis.

METHODS

In a cohort study at a university-based adult cystic fibrosis program, 75 consecutive adult cystic fibrosis patients who had P. aeruginosa isolated from sputum cultures were studied over a 4-year period. Outcomes included decline in FEV1, clinic visits, hospitalizations, courses and days of intravenous antibiotics, and lung transplantation. Multiple linear and Poisson regression for repeated measures were used to assess the outcomes.

RESULTS

In comparison to patients with susceptible strains, patients with resistant P. aeruginosa had more severe baseline lung disease, more rapid decline in FEV1 (160 ml/year, p = 0.003) and were significantly more likely to undergo lung transplantation (17.6 vs. 0%, p = 0.005).

CONCLUSIONS

Infection with multiple-antibiotic-resistant P. aeruginosa is associated with accelerated progression of cystic fibrosis, and has important implications for infection control strategies, antibiotic use and lung transplantation.

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.

Host genetic factors and mycobacterial infections: lessons from single gene disorders affecting innate and adaptive immunity

This review summarizes the association of increased susceptibility to mycobacterial disease in patients with genetic defects affecting innate and adaptive immunity. The optimum function of CD4 T-cell and macrophage function is critically important for immunity against mycobacteria. Antibody, complement and neutrophil function is not required for effective anti-mycobacterial immunity.

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.

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.

Cystic fibrosis lung disease: genetic influences, microbial interactions, and radiological assessment

Cystic fibrosis (CF) is a multiorgan disease caused by mutation of the CF transmembrane conductance regulator (CFTR) gene. Obstructive lung disease is the predominant cause of morbidity and mortality; thus, most efforts to improve outcomes are directed toward slowing or halting lung-disease progression. Current therapies, such as mucolytics, airway clearance techniques, bronchodilators, and antibiotics, aim to suppress airway inflammation and the processes that stimulate it, namely, retention and infection of mucus plaques at the airway surface. New approaches to therapy that aim to ameliorate specific CFTR mutations or mutational classes by restoring normal expression or function are being investigated. Because of its sensitivity in detecting changes associated with early airway obstruction and regional lung disease, high-resolution CT (HRCT) complements pulmonary function testing in defining disease natural history and measuring response to both conventional and experimental therapies. In this review, perspectives on the genetics and microbiology of CF provide a context for understanding the increasing importance of HRCT and other imaging techniques in assessing CF therapies.

Mycobactéries atypiques et mucoviscidose

Patients with cystic fibrosis are particularly at risk of infection with non-tuberculous mycobacteria (NTM). Prevalence of these infections increases with age to around 15 %. The main species involved are M. abscessus and M. avium, the latter not found in children under 15. Diagnosis relies on clinical, radiological and above all bacteriological criteria defined by the ATS. Identification of the causal species of NTM is essential and requires genetic techniques, some of which are currently evaluated. Treatment depends on the mycobacterial species. For M. avium, combined therapy with rifampicin, clarithromycin and ethambutol must be extended 12 months after negativation. M. abscessus infection is particularly resistant to therapy. Usual treatment is a one month course of intravenous imipenem or cefoxitin plus amikacin followed by oral clarithromycin plus ethambutol for at least 12 months after negativation. In case of local lesions, surgery is an option.

Prospective evaluation of emerging bacteria in cystic fibrosis

BACKGROUND

Bacteria contribute considerably to the progression of lung disease in cystic fibrosis. In this prospective, multi-centre study, we aimed to evaluate the occurrence of emerging bacteria and the physicians' assessments of the clinical importance of these findings.

METHODS

Twelve CF centres (total number of patients: 1419) reported the detection of any Stenotrophomonas maltophilia, Burkholderia cepacia complex, MRSA, Alcaligenes xylosoxidans, Klebsiella species and Mycobacteria during an observation period of 6 months.

RESULTS

213 specimens with emerging bacteria were reported from 145 different patients. The proportion of patients with emerging bacteria differed between centres (3-38%, mean: 12.6%) and increased with age. The predominant bacterium was S. maltophilia (n=106 positive specimens), followed by Klebsiellae (n=36), B. cepacia complex (n=31), A. xylosoxidans (n=16), Mycobacteria (n=11), MRSA (n=11), and others (n=2). In many instances the same microorganisms had already been reported earlier, indicating intermittent or chronic colonisation. The clinical status was reported to be stable in 70% of patients, and antibiotic treatment was anticipated for 46% of positive specimens. Comparison of clinical data to age matched controls did not reveal any significant differences with regard to pulmonary and nutritional status prior to detection of emerging bacteria.

CONCLUSION

These data suggest a high variability between centres regarding the prevalence of emerging bacteria. Most patients maintained a stable clinical condition during the 6-month study period despite being colonised with emerging bacteria.

Nontuberculous mycobacterial infection in young children with cystic fibrosis

Although nontuberculous mycobacteria (NTM) are recognized pathogens in adolescent and adult patients with cystic fibrosis (CF), the role of NTM in younger CF patients is not well-defined. To explore NTM infection in CF patients less than 12 years old, a retrospective review was performed. Prevalence was estimated from routine mycobacterial cultures of bronchoalveolar lavage (BAL) specimens collected over a 3-year period. NTM-positive cultures were obtained from 9 of 258 BALs collected from 7 of 114 different patients (5 months to 11 years of age). Further data were acquired from microbiological and clinical records of all pediatric patients with CF over a 10-year period. A total of 17 patients had at least one positive mycobacterial culture at less than 12 years of age, 5 of whom had positive cultures before age 5. The most commonly identified organisms were Mycobacterium avium-complex and Mycobacterium abscessus. Of the 17 patients, 10 met American Thoracic Society (ATS) microbiological criteria for mycobacterial disease, and 7 did not. The two groups did not differ with respect to age, gender, or presence of other respiratory pathogens. Patients who met ATS microbiological criteria for disease were more likely to have positive smears for acid-fast bacilli and grow Mycobacterium abscessus from culture. These patients also had a greater decline in lung function over time than patients who did not meet the microbiologic criteria. These data suggest that NTM represent a clinically significant pathogen, even in young patients with cystic fibrosis.

Antiinflammatory Therapies for Cystic Fibrosis: Past, Present, and Future

Inflammation is a major component of the vicious cycle characterizing cystic fibrosis pulmonary disease. If untreated, this inflammatory process irreversibly damages the airways, leading to bronchiectasis and ultimately respiratory failure. Antiinflammatory drugs for cystic fibrosis lung disease appear to have beneficial effects on disease parameters. These agents include oral corticosteroids and ibuprofen, as well as azithromycin, which, in addition to its antimicrobial effects, also possesses antiinflammatory properties. Inhaled corticosteroids, colchicine, methotrexate, montelukast, pentoxifylline, nutritional supplements, and protease replacement have not had a significant impact on the disease. Therapy with oral corticosteroids, ibuprofen, and fish oil is limited by adverse effects. Azithromycin appears to be safe and effective, and is thus the most promising antiinflammatory therapy available for patients with cystic fibrosis. Pharmacologic therapy with antiinflammatory agents should be started early in the disease course, before extensive irreversible lung damage has occurred.

Late Diagnosis Defines a Unique Population of Long-term Survivors of Cystic Fibrosis

Although the median survival for patients with cystic fibrosis (CF) is 32.9 years, a small group of patients live much longer. We analyzed the genotype and phenotype of CF patients 40 years and older seen between 1992 and 2004 at the National Jewish Medical and Research Center (n = 55). These patients were divided into two groups according to age at diagnosis: an early diagnosis (ED) group, median age at diagnosis 2.0 years (range 0.1-15 years, n = 28), and a late diagnosis (LD) group, median age of diagnosis 48.8 years (range 24-72.8 years, n = 27). Consistent with the hypothesis that the CFTR genotype affects the age at diagnosis, CFTR DeltaF508 homozygous individuals were more common in the ED group. Although patients in the ED group were predominantly male, the majority of LD patients were female. Patients with CF diagnosed late had a significantly lower prevalence of pancreatic insufficiency and CF-related diabetes, and better lung function. Fewer patients in the LD groups were infected with Pseudomonas aeruginosa, whereas a greater percentage had cultures positive for nontuberculous mycobacteria. This is the largest cohort of older patients with CF described to date, and our findings indicate that patients diagnosed as adults differ distinctly from survivors of long-term CF diagnosed as children.

Update on cystic fibrosis epidemiology

PURPOSE OF REVIEW

With the improving survival of cystic fibrosis (CF) patients, the clinical spectrum of this complex multisystem disease continues to evolve. Epidemiologic studies have provided important insight into the disease course, prognosis, and complications. This review summarizes recent advances in our understanding of predictors of survival and outcome and modifiers of disease in CF. This review is not meant to be comprehensive, but highlights selected studies, many of which have particular relevance to the growing number of older CF patients.

RECENT FINDINGS

Survival rates of US CF patients improved remarkably over the past 15 years, but most of the improvement was limited to patients 2 to 15 years of age. Both median household income and ambient air pollutants were found to be important modifiers of disease, echoing research reported in other chronic lung diseases. Genotype classified according to functional mutation class was highly associated with outcome (class I, II, and III mutations were associated with the highest mortality). Of the emerging pathogens, B. cepacia complex and B. gladioli are the most prominent. A small but significant percentage of patients have been shown to acquire new B. cepacia complex or B. gladioli strains with time.

SUMMARY

Epidemiologic research in cystic fibrosis continues to inform patient care and clinical research, and to generate new hypotheses regarding pathophysiology. Survival and outcomes continue to improve in this multisystem disease. With continued improving survival, epidemiologic studies will be critical to tracking changes in prognosis and outcome.

Mycobacteria in drinking water distribution systems: ecology and significance for human health

In contrast to the notorious pathogens Mycobacterium tuberculosis and M. leprae, the majority of the mycobacterial species described to date are generally not considered as obligate human pathogens. The natural reservoirs of these non-primary pathogenic mycobacteria include aquatic and terrestrial environments. Under certain circumstances, e.g., skin lesions, pulmonary or immune dysfunctions and chronic diseases, these environmental mycobacteria (EM) may cause disease. EM such as M. avium, M. kansasii, and M. xenopi have frequently been isolated from drinking water and hospital water distribution systems. Biofilm formation, amoeba-associated lifestyle, and resistance to chlorine have been recognized as important factors that contribute to the survival, colonization and persistence of EM in water distribution systems. Although the presence of EM in tap water has been linked to nosocomial infections and pseudo-infections, it remains unclear if these EM provide a health risk for immunocompromised people, in particular AIDS patients. In this regard, control strategies based on maintenance of an effective disinfectant residual and low concentration of nutrients have been proposed to keep EM numbers to a minimum in water distribution systems.

Measurement of Immunoglobulin G against Mycobacterial Antigen A60 in Patients with Cystic Fibrosis and Lung Infection Due to Mycobacterium abscessus

BACKGROUND

The diagnosis and prognosis of lung infections due to the emerging nontuberculous mycobacterium (NTM) Mycobacterium abscessus are difficult to establish in children with cystic fibrosis.

METHODS

We evaluated the usefulness of an enzyme-linked immunosorbent assay for detecting serum IgG antibodies against the ubiquitous mycobacterial antigen A60.

RESULTS

A total of 186 patients with cystic fibrosis (mean age+/-SD, 12.0+/-5.0 years) were studied, including 15 M. abscessus-positive patients who fulfilled American Thoracic Society (ATS) criteria for NTM infection (M. abscessus-infected patients), 7 M. abscessus-positive patients who did not fulfill ATS criteria, 20 patients positive for various other NTM who did not fulfill ATS criteria, and 144 NTM-negative control patients; mean IgG titers (+/-SD) for these 4 groups were 718+/-342 U, 193+/-113 U, 129+/-49 U, and 121+/-53 U, respectively (M. abscessus-infected patients vs. each of the other groups, P<.005). The A60 IgG test was both sensitive (approximately 87%) and specific (approximately 95%) if adapted cutoff values were used (150 U and 250 U for patients aged <or=10 years and patients aged >10 years, respectively) and correlated well with results of acid-fast bacilli smears.

CONCLUSION

Measurement of anti-A60 IgG may be useful for both the diagnosis and assessment of activity of M. abscessus lung infection in persons with cystic fibrosis.

The use of macrolide antibiotics in patients with cystic fibrosis

PURPOSE OF REVIEW

There has been much recent interest in the use of macrolide antibiotics as chronic suppressive therapy in patients with cystic fibrosis. Three recent randomized, placebo-controlled trials have been conducted.

RECENT FINDINGS

All three trials used similar regimens of azithromycin, and lung function improved after 3 to 6 months of treatment. The relative change in forced expiratory volume in 1 second predicted improved between 3.6% and 6.2%. Furthermore, the azithromycin treatment groups had improvement in a variety of secondary outcomes related to pulmonary exacerbations, including a reduction in antibiotic use (both intravenous and oral) and hospitalization rate. Furthermore, azithromycin was well tolerated: Only nausea, diarrhea, and wheezing (described as mild to moderate) occurred more frequently in the azithromycin group compared with the placebo group. The evidence for the clinical benefit of azithromycin in cystic fibrosis has been summarized in a Cochrane review in which a meta-analysis confirmed a significant improvement in forced expiratory volume in 1 second among the 286 pooled participants.

SUMMARY

Azithromycin has entered the therapeutic armamentarium for patients with cystic fibrosis who are chronically infected with Pseudomonas aeruginosa. Improved lung function, a reduction in pulmonary exacerbations and antibiotic use, and weight gain are potential benefits of this drug. Future studies should address the use of azithromycin in other cystic fibrosis patient populations, including those patients without chronic infection with P. aeruginosa, children younger than 6 years of age, and those infected with Burkholderia cepacia complex. The mechanism of action of macrolide antibiotics in cystic fibrosis remains unknown.

Prospective study on nontuberculous mycobacteria in patients with and without cystic fibrosis

Recent reports indicated an increase of nontuberculous mycobacteria (NTM) in cystic fibrosis (CF) patients. However, it is still a matter of discussion whether criteria for diagnosis of NTM pulmonary infection established by the American Thoracic Society (ATS) are applicable for CF patients. We determined incidence and prevalence of NTM in CF patients and non-CF patients without HIV infection, and validity of ATS criteria for CF patients. Over a period of 2 years, 1,251 respiratory samples were investigated for mycobacteria from 91 CF and 162 non-CF patients. For all patients with NTM recovery, we reviewed clinical charts and determined outcome for up to 2 years. Incidence and prevalence for repeated recovery of NTM were higher in CF patients, but not significantly. CF patients with repeated recovery of NTM met clinical and bacteriological ATS criteria, but radiographic criteria were not met. Treated CF patients showed favorable clinical outcomes, as opposed to untreated patients. We propose a modified definition for diagnosis and hence treatment of NTM pulmonary infection in CF patients.

Mycobacterium avium complex pulmonary disease in patients without HIV infection

Mycobacterium avium complex (MAC) is ubiquitous. It is found in various freshwater and saltwater sources around the world, including hot water pipes. Although the organism was identified in the 1890s, its potential to cause human disease was only recognized 50 years later. Only a minority of people exposed to the organism will acquire MAC lung disease, usually those with underlying lung disease or immunosuppression. MAC may, however, cause progressive parenchymal lung disease and bronchiectasis in patients without underlying lung disease, particularly in middle-aged and elderly women. Preliminary data suggest that the interferon-gamma pathways may be deficient in elderly women with MAC lung disease. Other groups of patients who are more likely to harbor MAC in their lungs include patients with a cystic fibrosis or an abnormal alpha(1)-antiproteinase gene and patients with certain chest wall abnormalities. Treatment results continue to be disappointing, and the mortality of patients with MAC lung disease remains high. A PubMed search identified 38 reports of the treatment of MAC lung disease. Apart from the British Thoracic Society study, the only published controlled investigation, the studies published since 1994 have included a macrolide, either clarithromycin or azithromycin, usually in combination with ethambutol and a rifamycin. If success is defined as eradication of the organism without relapse over a period of several years after treatment has been discontinued, the reported treatment success rate with the macrolide containing regimens is approximately 55%. The prolonged treatment period, side effects, and possibly reinfection rather than relapse are responsible for the high failure rate.

Early intervention and prevention of lung disease in cystic fibrosis: a European consensus

In patients with cystic fibrosis (CF), early intervention and prevention of lung disease is of paramount importance. Principles to achieve this aim include early diagnosis of CF, regular monitoring of the clinical status, various hygienic measures to prevent infection and cross-infection, early use of antibiotic courses in patients with recurrent or continuous bacterial colonisation and appropriate use of chest physiotherapy.

Detection of mycobacterial DNA from sputum of patients with cystic fibrosis

BACKGROUND

Patients with cystic fibrosis (CF) are at high risk from atypical mycobacterial infections. There have been few attempts to delineate the intensity of mycobacterial infection in CF patients in Ireland.

AIMS

To examine the incidence of mycobacterial DNA in an archived collection of genomic DNA extracted from the sputa of CF patients within the Northern Ireland population.

METHODS

One hundred and eighty-two CF patients (66 adults and 116 children) were examined for the presence of mycobacterial DNA in their sputum by a genus specific PCR assay based on 16S rRNA, followed by direct automated sequencing of the PCR amplicons.

RESULTS

One of 116 (0.9%) children and 2 of 66 adults were positive. Sequence identity revealed Mycobacterium xenopi in the paediatric patient and M. xenopi and M. chelonei in the two adult patients. False-positive results occurred in 11 patients (four adults), mainly due to Corynebacterium spp.

CONCLUSIONS

There was a low prevalence of Mycobacterium spp in the CF patient population. All PCR positive results should be confirmed by direct automated sequencing and an alternative specific assay employed. Enhanced molecular screening will contribute in understanding their role as opportunistic pathogens in patients with worsening lung function.

Infection control in cystic fibrosis

Over the past 20 years there has been a greater interest in infection control in cystic fibrosis (CF) as patient-to-patient transmission of pathogens has been increasingly demonstrated in this unique patient population. The CF Foundation sponsored a consensus conference to craft recommendations for infection control practices for CF care providers. This review provides a summary of the literature addressing infection control in CF. Burkholderia cepacia complex, Pseudomonas aeruginosa, and Staphylococcus aureus have all been shown to spread between patients with CF. Standard precautions, transmission-based precautions including contact and droplet precautions, appropriate hand hygiene for health care workers, patients, and their families, and care of respiratory tract equipment to prevent the transmission of infectious agents serve as the foundations of infection control and prevent the acquisition of potential pathogens by patients with CF. The respiratory secretions of all CF patients potentially harbor clinically and epidemiologically important microorganisms, even if they have not yet been detected in cultures from the respiratory tract. CF patients should be educated to contain their secretions and maintain a distance of >3 ft from other CF patients to avoid the transmission of potential pathogens, even if culture results are unavailable or negative. To prevent the acquisition of pathogens from respiratory therapy equipment used in health care settings as well as in the home, such equipment should be cleaned and disinfected. It will be critical to measure the dissemination, implementation, and potential impact of these guidelines to monitor changes in practice and reduction in infections.

Antimicrobial susceptibility and synergy studies of Stenotrophomonas maltophilia isolates from patients with cystic fibrosis

Stenotrophomonas maltophilia is a newly emerging pathogen being detected with increasing frequency in patients with cystic fibrosis (CF). The impact of this multidrug-resistant organism on lung function is uncertain. The optimal treatment for S. maltophilia in CF patients is unknown. We studied the in vitro activity of ten antimicrobial agents, and conducted synergy studies by using checkerboard dilutions of eight pairs of antimicrobial agents against strains isolated from 673 CF patients from 1996 to 2001. This represents approximately 7 to 23% of the CF patients in the United States who harbor S. maltophilia annually. Doxycycline was the most active agent and inhibited 80% of 673 initial patient isolates, while trimethoprim-sulfamethoxazole inhibited only 16%. High concentrations of colistin proved more active than high concentrations of tobramycin and gentamicin. Serial isolates (n = 151) from individual patients over time (median, 290 days) showed minimal changes in resistance. Synergistic or additive activity was demonstrated by trimethoprim-sulfamethoxazole paired with ticarcillin-clavulanate (65% of strains), ciprofloxacin paired with ticarcillin-clavulanate (64% of strains), ciprofloxacin paired with piperacillin-tazobactam (59% of strains), trimethoprim-sulfamethoxazole paired with piperacillin-tazobactam (55% of strains), and doxycycline paired with ticarcillin-clavulanate (49% of strains). In all, 522 (78%) isolates were multidrug resistant (i.e., resistant to all agents in two or more antimicrobial classes) but 473 (91%) of these were inhibited by at least one antimicrobial combination (median, four; range, one to eight). To determine appropriate treatment for patients with CF, it is important to monitor the prevalence, antimicrobial susceptibility, and clinical impact of S. maltophilia in this patient population.

Primary ciliary dyskinesia: diagnostic and phenotypic features

Primary ciliary dyskinesia (PCD) is a genetic disease characterized by abnormalities in ciliary structure/function. We hypothesized that the major clinical and biologic phenotypic markers of the disease could be evaluated by studying a cohort of subjects suspected of having PCD. Of 110 subjects evaluated, PCD was diagnosed in 78 subjects using a combination of compatible clinical features coupled with tests of ciliary ultrastructure and function. Chronic rhinitis/sinusitis (n = 78; 100%), recurrent otitis media (n = 74; 95%), neonatal respiratory symptoms (n = 57; 73%), and situs inversus (n = 43; 55%) are strong phenotypic markers of the disease. Mucoid Pseudomonas aeruginosa (n = 12; 15%) and nontuberculous mycobacteria (n = 8; 10%) were present in older (> 30 years) patients with PCD. All subjects had defects in ciliary structure, 66% in the outer dynein arm. Nasal nitric oxide production was very low in PCD (nl/minute; 19 +/- 17 vs. 376 +/- 124 in normal control subjects). Rigorous clinical and ciliary phenotyping and measures of nasal nitric oxide are useful for the diagnosis of PCD. An increased awareness of the clinical presentation and diagnostic criteria for PCD will help lead to better diagnosis and care for this orphan disease.

Pathophysiology and management of pulmonary infections in cystic fibrosis

This comprehensive State of the Art review summarizes the current published knowledge base regarding the pathophysiology and microbiology of pulmonary disease in cystic fibrosis (CF). The molecular basis of CF lung disease including the impact of defective cystic fibrosis transmembrane regulator (CFTR) protein function on airway physiology, mucociliary clearance, and establishment of Pseudomonas aeruginosa infection is described. An extensive review of the microbiology of CF lung disease with particular reference to infection with P. aeruginosa is provided. Other pathogens commonly associated with CF lung disease including Staphylococcal aureus, Burkholderia cepacia, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and atypical mycobacteria are also described. Clinical presentation and assessment of CF lung disease including diagnostic microbiology and other measures of pulmonary health are reviewed. Current recommendations for management of CF lung disease are provided. An extensive review of antipseudomonal therapies in the settings of treatment for early P. aeruginosa infection, maintenance for patients with chronic P. aeruginosa infection, and treatment of exacerbation in pulmonary symptoms, as well as antibiotic therapies for other CF respiratory pathogens, are included. In addition, the article discusses infection control policies, therapies to optimize airway clearance and reduce inflammation, and potential future therapies.

Controlled trial of continuous positive airway pressure in obstructive sleep apnea and heart failure

Obstructive sleep apnea (OSA) is highly prevalent among patients with congestive heart failure (CHF) and may contribute to progression of cardiac dysfunction via hypoxia, elevated sympathetic nervous system activity, and systemic hypertension. Our aim was to assess the long-term effect of OSA treatment with nocturnal continuous positive airway pressure (CPAP) on systolic heart function, sympathetic activity, blood pressure, and quality of life in patients with CHF. Fifty-five patients with CHF and OSA were randomized to 3 months of CPAP or control groups. End points were changes in left ventricular ejection fraction, overnight urinary norepinephrine excretion, blood pressure, and quality of life. Nineteen patients in the CPAP group and 21 control subjects completed the study. Compared with the control group, CPAP treatment was associated with significant improvements in left ventricular ejection fraction (delta 1.5 +/- 1.4% vs. 5.0 +/- 1.0%, respectively, p = 0.04), reductions in overnight urinary norepinephrine excretion (delta 1.6 +/- 3.7 vs. -9.9 +/- 3.6 nmol/mmol creatinine, p = 0.036), and improvements in quality of life. There were no significant changes in systemic blood pressure. In conclusion, treatment of OSA among patients with CHF leads to improvement in cardiac function, sympathetic activity, and quality of life.