Lung transplant outcomes in cystic fibrosis patients with pre-operativeMycobacterium abscessusrespiratory infections

The Many Hosts of Mycobacteria 9 (MHM9): A conference report

The Many Hosts of Mycobacteria (MHM) meeting series brings together basic scientists, clinicians and veterinarians to promote robust discussion and dissemination of recent advances in our knowledge of numerous mycobacterial diseases, including human and bovine tuberculosis (TB), nontuberculous mycobacteria (NTM) infection, Hansen's disease (leprosy), Buruli ulcer and Johne's disease. The 9th MHM conference (MHM9) was held in July 2022 at The Ohio State University (OSU) and centered around the theme of "Confounders of Mycobacterial Disease." Confounders can and often do drive the transmission of mycobacterial diseases, as well as impact surveillance and treatment outcomes. Various confounders were presented and discussed at MHM9 including those that originate from the host (comorbidities and coinfections) as well as those arising from the environment (e.g., zoonotic exposures), economic inequality (e.g. healthcare disparities), stigma (a confounder of leprosy and TB for millennia), and historical neglect (a confounder in Native American Nations). This conference report summarizes select talks given at MHM9 highlighting recent research advances, as well as talks regarding the historic and ongoing impact of TB and other infectious diseases on Native American Nations, including those in Southwestern Alaska where the regional TB incidence rate is among the highest in the Western hemisphere.

Mycobacteria in Organ Transplant Recipients

This review describes the epidemiology and risk factors of tuberculosis (TB) in solid organ transplant recipients. We discuss the pre-transplant screening for risk of TB and management of latent TB in this population. We also discuss the challenges of management of TB and other difficult to treat mycobacteria such as Mycobacterium abscessus and Mycobacterium avium complex. The drugs for the management of these infections include rifamycins which have significant drug interactions with immunosuppressants and must be monitored closely.

Update on Lung Transplantation for Cystic Fibrosis

Lung transplantation provides a treatment option for many individuals with advanced lung disease due to cystic fibrosis (CF). Since the first transplants for CF in the 1980s, survival has improved and the opportunity for transplant has expanded to include individuals who previously were not considered candidates for transplant. Criteria to be a transplant candidate vary significantly among transplant programs, highlighting that the engagement in more than one transplant program may be necessary. Individuals with highly resistant CF pathogens, malnutrition, osteoporosis, CF liver disease, and other comorbidities may be suitable candidates for lung transplant, or if needed, multi-organ transplant. The transplant process involves several phases, from discussion of prognosis and referral to a transplant center, to transplant evaluation, to listing, transplant surgery, and care after transplant. While the availability of highly effective CF transmembrane conductance regulator (CFTR) modulators for many individuals with CF has improved lung function and slowed progression to respiratory failure, early discussion regarding transplant as a treatment option and referral to a transplant program are critical to maximizing opportunity and optimizing patient and family experience. The decision to be evaluated for transplant and to list for transplant are distinct, and early referral may provide a treatment option that can be urgently executed if needed. Survival after transplant for CF is improving, to a median survival of approximately 10 years, and most transplant survivors enjoy significant improvement in quality of life.

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.

Opportunistic Pathogens in Cystic Fibrosis: Epidemiology and Pathogenesis of Lung Infection

Cystic fibrosis (CF) is one of the most common life-shortening genetic diseases in Caucasians. Due to abnormal accumulation of mucus, respiratory failure caused by chronic infections is the leading cause of mortality in this patient population. The microbiology of these respiratory infections includes a distinct set of opportunistic pathogens, including Pseudomonas aeruginosa, Burkholderia spp., Achromobacter spp., Stenotrophomonas maltophilia, anaerobes, nontuberculous mycobacteria, and fungi. In recent years, culture-independent methods have shown the polymicrobial nature of lung infections, and the dynamics of microbial communities. The unique environment of the CF airway predisposes to infections caused by opportunistic pathogens. In this review, we will highlight how the epidemiology and role in disease of these pathogens in CF differ from that in individuals with other medical conditions. Infectious diseases (ID) physicians should be aware of these differences and the specific characteristics of infections associated with CF.

Molecular Epidemiology of Mycobacterium abscessus Isolates Recovered from German Cystic Fibrosis Patients

Infections due to Mycobacterium abscessus are a major cause of mortality and morbidity in cystic fibrosis (CF) patients. Furthermore, M. abscessus has been suspected to be involved in person-to-person transmissions. In 2016, dominant global clonal complexes (DCCs) that occur worldwide among CF patients have been described. To elucidate the epidemiological situation of M. abscessus among CF patients in Germany and to put these data into a global context, we performed whole-genome sequencing of a set of 154 M. abscessus isolates from 123 German patients treated in 14 CF centers. We used MTBseq pipeline to identify clusters of closely related isolates and correlate those with global findings. Genotypic drug susceptibility for macrolides and aminoglycosides was assessed by characterization of the erm(41), rrl, and rrs genes. By this approach, we could identify representatives of all major DCCs (Absc 1, Absc 2, and Mass 1) in our cohort. Intrapersonal isolates showed higher genetic relatedness than interpersonal isolates (median 3 SNPs versus 16 SNPs; P < 0.001). We further identified four clusters with German patients from same centers clustering with less than 25 SNPs distance (range 3 to 18 SNPs) but did not find any hint for in-hospital person-to-person transmission. This is the largest study investigating phylogenetic relations of M. abscessus isolates in Germany. We identified representatives of all reported DCCs but evidence for nosocomial transmission remained inconclusive. Thus, the occurrence of genetically closely related isolates of M. abscessus has to be interpreted with care, as a direct interhuman transmission cannot be directly deduced. IMPORTANCE Mycobacterium abscessus is a major respiratory pathogen in cystic fibrosis (CF) patients. Recently it has been shown that dominant global clonal complexes (DCCs) have spread worldwide among CF patients. This study investigated the epidemiological situation of M. abscessus among CF patients in Germany by performing whole-genome sequencing (WGS) of a set of 154 M. abscessus from 123 German patients treated in 14 CF centers. This is the largest study investigating the phylogenetic relationship of M. abscessus CF isolates in Germany.

Antibiotic Therapy for Difficult-to-Treat Infections in Lung Transplant Recipients: A Practical Approach

Lung transplant recipients are at higher risk to develop infectious diseases due to multi-drug resistant pathogens, which often chronically colonize the respiratory tract before transplantation. The emergence of these difficult-to-treat infections is a therapeutic challenge, and it may represent a contraindication to lung transplantation. New antibiotic options are currently available, but data on their efficacy and safety in the transplant population are limited, and clinical evidence for choosing the most appropriate antibiotic therapy is often lacking. In this review, we provide a summary of the best evidence available in terms of choice of antibiotic and duration of therapy for MDR/XDR P. aeruginosa, Burkholderia cepacia complex, Mycobacterium abscessus complex and Nocardia spp. infections in lung transplant candidates and recipients.

Cystic fibrosis: candidate selection and impact of the cystic fibrosis transmembrane conductance regulator therapy

PURPOSE OF REVIEW

Over the past decade, the development of highly effective cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulators has dramatically ameliorated the manifestations of CF for most patients. Perhaps most importantly, CFTR modulators impact the development and progression of advanced lung disease (ALD) and are changing the CF population accessing lung transplant.

RECENT FINDINGS

A recent phase 3 trial of elexacaftor/tezacaftor/ivacaftor (ETI) demonstrated efficacy for individuals with at least one copy of the most common CF mutation, F508del. Studies of CFTR modulator therapy in patients with ALD have demonstrated similar improvements in lung function, nutrition, and pulmonary exacerbation frequency as seen in individuals with higher lung function. Due to improvements with ETI, rates of lung transplant for CF have declined and individuals are achieving stability in lung function. Nevertheless, the Cystic Fibrosis Foundation guidelines for lung transplant referral should be used to guide referral decisions for all individuals with CF, including those on CFTR modulator therapy, to allow remediation of modifiable barriers to transplant. ETI may be used in the posttransplant setting but for selected individuals and with close monitoring.

SUMMARY

Increasing access to highly effective CFTR modulators has changed the trajectory of lung disease in CF for many, but not all, individuals and there remain individuals who cannot access therapy or whose mutations do not respond to modulators. Lung transplant remains an important treatment option for individuals with advanced CF lung disease. Increasing attention will be required to optimize decisions of when to list for transplant.

Bacterial infections in lung transplantation

Lung transplantation has lower survival rates compared to other than other solid organ transplants (SOT) due to higher rates of infection and rejection-related complications, and bacterial infections (BI) are the most frequent infectious complications. Excess morbidity and mortality are not only a direct consequence of these BI, but so are subsequent loss of allograft tolerance, rejection, and chronic lung allograft dysfunction due to bronchiolitis obliterans syndrome (BOS). A wide variety of pathogens can cause infections in lung transplant recipients (LTRs), including a number of nosocomial pathogens and other multidrug-resistant (MDR) pathogens. Although pneumonia and intrathoracic infections predominate, LTRs are at risk of a number of types of infections. Risk factors include altered anatomy and function of airways, impaired immunity, the microbial flora of the donor and recipient, underlying medical conditions, and genetic factors. Further work on immune monitoring has the potential to improve outcomes. The infecting agents can be derived from the donor lung, pre-existing recipient flora, or acquired from the environment over time. Certain infections may preclude lung transplantation, but this varies from center to center, and more recent studies suggest fewer patients should be disqualified. New molecular methods allow microbiome studies of the lung, gut, and other sites that may further our knowledge of how airway colonization can result in infection and allograft loss. Surveillance, early diagnosis, and aggressive antimicrobial therapy of BI is critical in LTRs. Antibiotic resistance is a major barrier to successful management of these infections. The availability of new agents for MDR Gram-negatives may improve outcomes. Other new therapies, such as bacteriophage therapy, show promise for the future. Finally, it is important to prevent infections through peri-transplant prophylaxis, vaccination, and infection control measures.

Consensus document for the selection of lung transplant candidates: An update from the International Society for Heart and Lung Transplantation

Tens of thousands of patients with advanced lung diseases may be eligible to be considered as potential candidates for lung transplant around the world each year. The timing of referral, evaluation, determination of candidacy, and listing of candidates continues to pose challenges and even ethical dilemmas. To address these challenges, the International Society for Heart and Lung Transplantation appointed an international group of members to review the literature, to consider recent advances in the management of advanced lung diseases, and to update prior consensus documents on the selection of lung transplant candidates. The purpose of this updated consensus document is to assist providers throughout the world who are caring for patients with pulmonary disease to identify potential candidates for lung transplant, to optimize the timing of the referral of these patients to lung transplant centers, and to provide transplant centers with a framework for evaluating and selecting candidates. In addition to addressing general considerations and providing disease specific recommendations for referral and listing, this updated consensus document includes an ethical framework, a recognition of the variability in acceptance of risk between transplant centers, and establishes a system to account for how a combination of risk factors may be taken into consideration in candidate selection for lung transplantation.

Whole Genome Sequencing in the Management of Non-Tuberculous Mycobacterial Infections

Infections caused by non-tuberculous mycobacteria (NTM) have been a public health problem in recent decades and contribute significantly to the clinical and economic burden globally. The diagnosis of infections is difficult and time-consuming and, in addition, the conventional diagnostics tests do not have sufficient discrimination power in species identification due to cross-reactions and not fully specific probes. However, technological advances have been made and the whole genome sequencing (WGS) method has been shown to be an essential part of routine diagnostics in clinical mycobacteriology laboratories. The use of this technology has contributed to the characterization of new species of mycobacteria, as well as the identification of gene mutations encoding resistance and virulence factors. Sequencing data also allowed to track global outbreaks of nosocomial NTM infections caused by M. abscessus complex and M. chimaera. To highlight the utility of WGS, we summarize recent scientific studies on WGS as a tool suitable for the management of NTM-induced infections in clinical practice.

Current and Emerging Therapies to Combat Cystic Fibrosis Lung Infections

The ultimate aim of any antimicrobial treatment is a better infection outcome for the patient. Here, we review the current state of treatment for bacterial infections in cystic fibrosis (CF) lung while also investigating potential new treatments being developed to see how they may change the dynamics of antimicrobial therapy. Treatment with antibiotics coupled with regular physical therapy has been shown to reduce exacerbations and may eradicate some strains. Therapies such as hypertonic saline and inhaled PulmozymeTM (DNase-I) improve mucus clearance, while modifier drugs, singly and more successfully in combination, re-open certain mutant forms of the cystic fibrosis transmembrane conductance regulator (CFTR) to enable ion passage. No current method, however, completely eradicates infection, mainly due to bacterial survival within biofilm aggregates. Lung transplants increase lifespan, but reinfection is a continuing problem. CFTR modifiers normalise ion transport for the affected mutations, but there is conflicting evidence on bacterial clearance. Emerging treatments combine antibiotics with novel compounds including quorum-sensing inhibitors, antioxidants, and enzymes, or with bacteriophages, aiming to disrupt the biofilm matrix and improve antibiotic access. Other treatments involve bacteriophages that target, infect and kill bacteria. These novel therapeutic approaches are showing good promise in vitro, and a few have made the leap to in vivo testing.

Outcome according to subspecies following lung transplantation in cystic fibrosis pediatric patients infected with Mycobacterium abscessus

BACKGROUND

Mycobacterium abscessus infection has been associated with variable outcomes following lung transplantation. M abscessus comprises three subspecies (M abscessus subsp abscessus, M abscessus subsp massiliense, and M abscessus subsp bolletii). We investigated whether lung transplantation outcome in cystic fibrosis (CF) patients in a single center was related to the M abscessus subspecies and genetic cluster.

METHODS

CF patients with chronic M abscessus infection transplanted at Great Ormond Street Hospital between 2004 and 2017 were retrospectively examined. All M abscessus isolates were identified to subspecies level by polymerase chain reaction and sequencing. Genetic cluster was determined by variable number tandem repeat profiling and whole-genome sequencing (WGS), and sequence type inferred from WGS.

RESULTS

Thirteen patients with chronic M abscessus infection underwent heart/lung or lung transplantation. Subspecies identification showed n = 1 with M abscessus bolletii, n = 5 with M abscessus massiliense, and n = 7 with M abscessus abscessus infection. Eight (62%) patients (one with M abscessus massiliense and seven with M abscessus abscessus) died post-lung transplant. The patient with M abscessus bolletii and three patients with M abscessus massiliense did well post-transplant. One patient with M abscessus massiliense is receiving ongoing treatment.

CONCLUSIONS

Dramatically worse outcomes are observed in patients infected with M abscessus subspecies abscessus, the majority of whom were infected with ST-1 and ST-26 strains. Patients infected with other M abcsessus strains can have acceptable outcomes.

Mycobacterium abscessus, an Emerging and Worrisome Pathogen among Cystic Fibrosis Patients

Nontuberculous mycobacteria (NTM) have recently emerged as important pathogens among cystic fibrosis (CF) patients worldwide. Mycobacterium abscessus is becoming the most worrisome NTM in this cohort of patients and recent findings clarified why this pathogen is so prone to this disease. M. abscessus drug therapy takes up to 2 years and its failure causes an accelerated lung function decline. The M. abscessus colonization of lung alveoli begins with smooth strains producing glycopeptidolipids and biofilm, whilst in the invasive infection, "rough" mutants are responsible for the production of trehalose dimycolate, and consequently, cording formation. Human-to-human M. abscessus transmission was demonstrated among geographically separated CF patients by whole-genome sequencing of clinical isolates worldwide. Using a M. abscessus infected CF zebrafish model, it was demonstrated that CFTR (cystic fibrosis transmembrane conductance regulator) dysfunction seems to have a specific role in the immune control of M. abscessus infections only. This pathogen is also intrinsically resistant to many drugs, thanks to its physiology and to the acquisition of new mechanisms of drug resistance. Few new compounds or drug formulations active against M. abscessus are present in preclinical and clinical development, but recently alternative strategies have been investigated, such as phage therapy and the use of β-lactamase inhibitors.

Indications for lung transplant referral and listing

Lung transplantation is a valuable therapeutic option for many patients with severe lung disease who have exhausted other medical or surgical therapies. However, since lungs are not a manufacturable organ like artificial heart valves or left ventricular assist devices, and since they are a limited resource compared to number of patients requiring the organs, the Department of Health and Human Services set the Final Rule of organ allocation in 1998. This led to development and implementation of Lung Allocation Score (LAS) in 2005. The score broadly divides lung diseases into 4 diagnostic criteria with a coefficient factor given to each category. The score is based on the prognostic factors of each patient to determine the risk of mortality without a transplant combined with the probability of patient survival post-transplant. Most of the guidelines for "Indications for referral and listing in lung transplant" is based on consensus opinion as there is limited amount of robust data and trials about this topic. The International Society for Heart and Lung Transplant (ISHLT) has published three editions for candidate selection and listing. In this article, we have attempted to highlight the guidelines and incorporated other disease specific prognostic factors that are not captured in the LAS. Ultimately, there are other factors like geographic location, height, blood group, preformed antibodies, transplant center experience, past wait times and transplant rate, availability of organs, etc., which also play a role especially when considering listing a patient for lung transplant. We also highlighted a representative disease in each category and most criteria for that disease will apply to other diseases in that category. Finally, this article does not delve into the history and reasoning behind each guideline but is meant to provide a general overview of indications and contraindications applicable in the field of adult lung transplantation.

Outcomes in Lung Transplant Recipients With Mycobacterium abscessus Infection: A 15-Year Experience From a Large Tertiary Care Center

BACKGROUND

Mycobacterium abscessus (M abscessus) infection is a serious complication post-lung transplant (LTx). We examined determinants of outcomes in LTx recipients infected with M abscessus.

METHODS

Electronic records of all patients who underwent LTx in a single transplant center between 2000 and 2015 were screened for isolation of M abscessus before or after LTx.

RESULTS

Twenty-six cases of M abscessus isolation were identified. Twenty-four had M abscessus isolation post-LTx. Two had M abscessus isolated from a surgical site, while the others were pulmonary isolates. Out of these 22 with pulmonary isolates, 12 had clinical disease. In 73% of patients, treatment had to be temporarily held or switched due to intolerance and toxicity. There was a statistically significant worsening in survival in those who developed clinical disease compared to matched controls. Among the 12 patients with clinical pulmonary disease, use of clofazimine was significantly associated with a favorable outcome. Six patients had M abscessus isolation pretransplant. Four developed M abscessus recurrence at a median of 2 months post-LTx. Two recurrences were surgical site infections, and 2 were pulmonary infections.

CONCLUSION

M abscessus infection is difficult to treat as tolerance to medications used is poor. M abscessus pneumonia is associated with worse survival post-LTx. Use of clofazimine is associated with 1-year infection-free survival.

Management of infections due to nontuberculous mycobacteria in solid organ transplant recipients-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the American Society of Transplantation Infectious Diseases Community of Practice review the epidemiology, diagnosis, prevention, and management of nontuberculous mycobacterial infections in the pre- and post-transplant period. NTM commonly cause one of five different clinical syndromes: pleuropulmonary disease, skin and soft tissue infection, osteoarticular infection, disseminated disease, including that caused by catheter-associated infection, and lymphadenitis. Diagnosis of these infections can be challenging, particularly when they are isolated from nonsterile spaces, owing to their ubiquity in nature. Consequently, diagnosis of pulmonary infections with these pathogens requires fulfillment of microbiologic, radiographic, and clinical criteria to address this concern. A combination of culture and molecular diagnostic techniques is often required to make a species-level identification. Treatment varies depending on the species isolated and is complex, owing to drug toxicities, need for long-term multidrug regimens, and consideration of complex drug-drug interactions between antimicrobials and immunosuppressive agents. Given these treatment challenges, efforts should be made in both the hospital and community settings to limit exposure to these pathogens to the extent feasible.

Cystic Fibrosis: From Qualification to Lung Transplantation, a Single Center Experience

Background

Cystic fibrosis (CF) is congenital multisystem disorder, that leads to gradual deterioration of pulmonary function. Advancements in therapy of CF-related lung disease have delayed its progression. However, lung transplantation remains the only therapeutic option for majority of such patients. Aim of the study was to assess qualification process and outcome of lung transplantation as a treatment of CF patients qualified in a single center between 2011 and 2018.

Material/Methods

This retrospective study assessed 41 patients who were qualified to be treated by means of lung transplantation due to CF in Lung Transplant Program of Silesian Center for Heart Diseases between 2011 and 2018. Analysis of patients during qualification process and after lung transplantation was performed. Lung recipients were observed during 1-year follow-up by means of pulmonary function tests.

Results

1-year survival was noted among 80% of the patients; 3-year survival and 5-year survival were noted among 70% of the recipients. Mean forced expiratory volume in 1 second (FEV1) increased after lung transplantation: 21.19% at qualification; and 76.67% at 12 months after lung transplantation. Mean forced vital capacity (FVC) results also improved: 34.18% at qualification and 78.34% at 12 months after lung transplantation. The 6-minute walk test (6MWT) before and after treatment noted an increase of 175.55 m.

Conclusions

Lung transplantation improves respiratory capacity of CF patients and prolongs their life.

Mycobacterium bolletii Lung Disease in Cystic Fibrosis

BACKGROUND

The cystic fibrosis (CF) pathogen, Mycobacterium abscessus complex, covers three subspecies: M. abscessus, M. massiliense, and M. bolletii. There are no clinical outcome data concerning M. bolletii. Our aim was to characterize M. bolletii lung infections in patients with CF.

METHODS

We included patients with M. bolletii lung infection recorded between 1994 and 2012 in France. Data were collected from the CF registry, medical records, and questionnaires submitted to the CF primary physician. Strains were typed by multilocus sequence typing analysis.

RESULTS

Fifteen cases were identified in nine CF centers. Nine patients (60%) presented with nontuberculous mycobacterial pulmonary disease. Follow-up of 13 patients showed a trend to more rapid decline in FEV₁ in the first year of colonization (-9.4%; SD 19.3) in comparison with noninfected control subjects (-2.3%; SD 12.1) (P = .16). Twelve patients were treated, and 11 received oral macrolides. Treatment-induced eradication occurred in five patients (41.7%). Four patients died (26.7%), including one patient with fatal nontuberculous mycobacterial pulmonary disease. Inducible macrolide resistance was demonstrated in all strains. Patients always harbored unique strains.

CONCLUSIONS

Our study reports the largest study cohort of CF patients infected with M. bolletii. M. bolletii infection affects both children and young adults, is most often symptomatic, and may be fatal. Macrolide-based therapies have poor effectiveness. There is no evidence of patient-to-patient transmission.

Mycobacterium abscessus: Environmental Bacterium Turned Clinical Nightmare

Mycobacteria are a large family of over 100 species, most of which do not cause diseases in humans. The majority of the mycobacterial species are referred to as nontuberculous mycobacteria (NTM), meaning they are not the causative agent of tuberculous (TB) or leprosy, i.e., Mycobacterium tuberculous complex and Mycobacterium leprae, respectively. The latter group is undoubtedly the most infamous, with TB infecting an estimated 10 million people and causing over 1.2 million deaths in 2017 alone TB and leprosy also differ from NTM in that they are only transmitted from person to person and have no environmental reservoir, whereas NTM infections are commonly acquired from the environment. It took until the 1950′s for NTM to be recognised as a potential lung pathogen in people with underlying pulmonary disease and another three decades for NTM to be widely regarded by the medical community when Mycobacterium avium complex was identified as the most common group of opportunistic pathogens in AIDS patients. This review focuses on an emerging NTM called Mycobacterium abscessus (M. abs). M. abs is a rapidly growing NTM that is responsible for opportunistic pulmonary infections in patients with structural lung disorders such as cystic fibrosis and bronchiectasis, as well as a wide range of skin and soft tissue infections in humans. In this review, we discuss how we came to understand the pathogen, how it is currently treated and examine drug resistance mechanisms and novel treatments currently in development. We highlight the urgent need for new and effective treatments for M. abs infection as well as improved in vivo methods of efficacy testing.

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.

Historical evolution of the diseases caused by non-pigmented rapidly growing mycobacteria in a University Hospital

OBJECTIVE

Non-pigmented rapidly growing mycobacteria (NPRGM) are a group of organisms of increasing interest due to the growing number of potential patients and the difficulties for a proper treatment in many of them. However, the evolution of these diseases in a long period of time and its evolutionary changes has been described only in a scanty number of reports.

METHODS

We performed a retrospective study between January 1st 2004 and December 31st 2017 in order to evaluate the clinical significance and types of diseases caused by NPRGM. Patients with isolates of NPRGM during this period were selected for the study, and clinical charts were reviewed using a predefined protocol.

RESULTS

During this period we identified 59 patients (76 clinical samples) with isolates of NPRGM, with 12 cases of clinical disease and one patient with doubtful significance (including 6 respiratory tract infections, 2 catheter infections, 1 skin and soft tissue infection, 1 disseminated infection, 1 conjunctivitis, 1 prosthetic joint infection and 1 mastitis). Fifty percent of M. chelonae isolates, 37.5% of M. abscessus isolates and 23.33% of M. fortuitum isolates were clinically significant. None of the isolates of other species were significant.

CONCLUSIONS

Most isolates in respiratory samples were contaminants/colonizations. M. abscessus was the main etiological agent in respiratory syndromes, whereas M. chelonae and M. fortuitum were more frequently associated with other infections, especially clinical devices and skin and soft tissue infections.

Common Infections Following Lung Transplantation

The lungs are the only transplanted organ in direct contact with the ‘outside world’. Infection is a significant cause of morbidity and mortality in lung transplantation. Early accurate diagnosis and optimal management is essential to prevent short and long term complications. Bacteria, including Mycobacteria and Nocardia, viruses and fungi are common pathogens. Organisms may be present in the recipient prior to transplantation, transmitted with the donor lungs or acquired after transplantation. The degree of immunosuppression and the routine use of antimicrobial prophylaxis alters the pattern of post-transplant infections.

The addition of avibactam renders piperacillin an effective treatment for Mycobacterium abscessus infection in an in vivo model

Treating M. abscessus infection is challenging due to the potent β-lactamase Bla_Mab (Beta-lactamase of M. abscessus ₎. Avibactam is a non-β-lactam, β-lactamase inhibitor shown to inhibit Bla_Mab. We tested whether avibactem can render piperacillin effective against M. Abscessus. In-vitro, avibactam enhanced the activity of piperacillin by 16-32 fold, with no significant effect on meropenem. In an in-vivo Galleria mellonella model, meropenem and piperacillin/avibactam significantly decreased infection burden compared to untreated controls. Neither piperacillin nor avibactam alone had a significant effect.

An Update in Antimicrobial Therapies and Infection Prevention in Pediatric Lung Transplant Recipients

Lung transplantation can offer life-prolonging therapy to children with otherwise terminal end-stage lung disease. However, infectious complications, like those experienced by their adult counterparts, are a significant cause of morbidity and mortality. These include bacteria, viruses, and fungi that infect the patient pretransplant and those that may be acquired from the donor or by the recipient in the months to years posttransplant. An understanding of the approach to the management of each potential infecting organism is required to ensure optimal outcomes. In particular, emphasis on aggressive preoperative management of infections in pediatric patients with cystic fibrosis is important. These include multidrug-resistant Gram-negative bacteria, fungi, and Mycobacterium abscessus, the posttransplant outcome of which depends on optimal pretransplant management, including vaccination and other preventive, antibiotic-sparing strategies. Similarly, increasing the transplant donor pool to meet rising transplant demands is an issue of critical importance. Expanded-criteria donors-those at increased risk of blood-borne viruses in particular-are increasingly being considered and transplants undertaken to meet the rising demand. There is growing evidence in the adult pool that these transplants are safe and associated with comparable outcomes. Pediatric transplanters are therefore likely to be presented with increased-risk donors for their patients. Finally, numerous novel antibiotic-sparing therapeutic approaches are on the horizon to help combat infections that currently compromise transplant outcomes.

Lung transplantation: indications and contraindications

The selection of appropriate recipients for lung transplantation is an evolving discipline. As experience with the procedure has developed over the last decades, the identification of transplant candidates has also changed as transplant centers strive to safely provide the therapy to as many patients possible. The International Society for Heart and Lung Transplantation (ISHLT) has developed three editions of recipient selection guidelines. Published in 1998, 2006, and 2015, these guidelines represented the best information relevant to the appropriate selection of lung transplant candidates. A discussion of areas supported by the most robust scientific data will be undertaken, but in many aspects of recipient selection, there is a paucity of data upon which to rely. Therefore, it is ultimately the prerogative and responsibility of individual centers to determine, after carefully weighing the best evidence available, whether a patient is deemed a suitable candidate at a specific program. All possible indications and contraindications for transplantation will be reviewed with attention also given to the appropriate timing of referral and listing of patients with advanced lung disease to a transplant center.

How can we improve the outcome for transplant patients with nontuberculous mycobacterial infections?

Nontuberculous mycobacteria (NTM) are environmental organisms that are rapidly emerging as pathogens in the transplant population. The prevalence of infection in transplant recipients remains unknown. While guidelines exist for treatment of NTM, neither the American Thoracic Society, the Infectious Diseases Society of America, nor the British Thoracic Society guidelines dictate the approach needed for transplant recipients. Here, we summarize risk factors, important diagnostic and treatment facts, and preventive measures to be taken to help improve outcomes of those infected with NTM infections.

NonTuberculous Mycobacteria infection and lung transplantation in cystic fibrosis: a worldwide survey of clinical practice

BACKGROUND

In people with cystic fibrosis infection with NonTuberculous Mycobacteria is of increasing prevalence. Mycobacterium abscessus complex is of particular concern and has been associated with adverse clinical outcomes. Optimal treatment usually requires multiple antibiotics for over 12 months. When considering lung transplantation for patients with NonTuberculous Mycobacteria potential benefits must be balanced against the risks of uncontrolled infection post-transplant and significant side-effects associated with treatment. In this survey we assessed current international practice with regard to assessing and listing patients for lung transplantation.

METHODS

We designed a questionnaire enquiring about local practice regarding screening for NonTuberculous Mycobacteria infection, specific contra-indications to transplantation, management and segregation of patients pre- and post-transplant. The survey was sent via e-mail to 37 paediatric and adult lung transplant centres across Europe, North America and Australia.

RESULTS

We gathered complete questionnaires from 21 centres (57% response rate). Few centres (29%) have a clear written policy regarding NonTuberculous Mycobacteria. Sixteen (76%) centres require molecular identification of NonTuberculous Mycobacteria species. Only four centres would consider infection with M. abscessus complex in itself a contra-indication for listing, however 76% regard it as a relative contra-indication. Eighty-six percent require treatment pre-transplantation. Finally, only 61% of centres had a clear policy regarding segration of patients pre-transplant and 48% post-transplant.

CONCLUSIONS

The issue of NonTuberculous Mycobacteria infection in people with cystic fibrosis requiring lung transplantation is well-recognized however current international recommendations are not detailed and there is variation in practice between centres. There is an urgent requirement for high quality clinical data to inform decision-making.

Non-tuberculous Mycobacterial Infections in Thoracic Transplant Candidates and Recipients

PURPOSE OF REVIEW

To review and discuss the epidemiology, risk factors, clinical presentation, diagnosis, and treatment of non-tuberculous mycobacteria (NTM) in thoracic transplantation.

RECENT FINDINGS

Non-tuberculous mycobacteria are ubiquitous but are an uncommon cause of disease after solid organ transplantation. The incidence of infection is higher in thoracic transplant recipients than in abdominal transplant recipients, with most cases seen after lung transplantation. It is associated with increased morbidity and, occasionally, mortality. Infection in the pre-transplant setting can occur in lung transplant candidates, often posing a dilemma regarding transplant listing. Disease manifestations are diverse, and pulmonary disease is the most common. Diagnosis requires a high index of suspicion. Treatment requires a multiple-drug combination and is limited by drug-drug interactions and tolerability. Mycobacterium abscessus is a challenge in lung transplant recipients, due to its intrinsic resistance and propensity to relapse even after prolonged therapy. Mycobacterium chimaera is an emerging pathogen associated with contamination of heater-cooler units and is described to cause disease months after cardiothoracic surgery. NTM infections in thoracic organ transplant recipients are uncommon but are associated with substantial morbidity and mortality. Data from larger multicenter studies is needed to better define the epidemiology of NTM in thoracic transplantation, best treatment options, and the management of infected transplant candidates.

Establishment and Validation of Galleria mellonella as a Novel Model Organism To Study Mycobacterium abscessus Infection, Pathogenesis, and Treatment

Treatment of Mycobacterium abscessus infections is extremely challenging due to its intrinsic resistance to most antibiotics, and research of pathogenesis is limited due to a lack of a practical in vivo model of infection. The objective of this study was to establish a simple in vivo model for M. abscessus infection, virulence, and drug testing in Galleria mellonella larvae. We inoculated larvae with M. abscessus bacteria and assessed histopathology, CFU count, and mortality with and without antibiotic treatment. We also constructed a luminescent, recombinant M. abscessus mutant, mDB158, and imaged infected larvae using the IVIS in vivo imaging system. M. abscessus proliferated and induced granuloma-like responses in infected larvae, leading to larval mortality. The G. mellonella model was further validated successfully by demonstration of the expected favorable antimicrobial effect of treatment with meropenem and the superiority of combination treatment (meropenem and tigecycline) over that with single agents. We then used IVIS imaging of larvae infected with luminescent M. abscessus, allowing live real-time assessment of bacterial load. We used this method to compare the antimicrobial effects of various antibiotics (meropenem, amikacin, linezolid, levofloxacin, etc.) on bacterial proliferation and larval survival. Meropenem and amikacin had the most favorable effects, correlating well with common clinical practice guidelines. These findings suggest G. mellonella to be an excellent in vivo model for research of M. abscessus infection, pathogenesis, and treatment. Luminescent M. abscessus and IVIS imaging further facilitates this model. Results obtained in this model clearly substantiated common clinical practice, thus validating the model as a predictor of treatment efficacy and outcome.

ECFS best practice guidelines: the 2018 revision

Developments in managing CF continue to drive dramatic improvements in survival. As newborn screening rolls-out across Europe, CF centres are increasingly caring for cohorts of patients who have minimal lung disease on diagnosis. With the introduction of mutation-specific therapies and the prospect of truly personalised medicine, patients have the potential to enjoy good quality of life in adulthood with ever-increasing life expectancy. The landmark Standards of Care published in 2005 set out what high quality CF care is and how it can be delivered throughout Europe. This underwent a fundamental re-write in 2014, resulting in three documents; center framework, quality management and best practice guidelines. This document is a revision of the latter, updating standards for best practice in key aspects of CF care, in the context of a fast-moving and dynamic field. In continuing to give a broad overview of the standards expected for newborn screening, diagnosis, preventative treatment of lung disease, nutrition, complications, transplant/end of life care and psychological support, this consensus on best practice is expected to prove useful to clinical teams both in countries where CF care is developing and those with established CF centres. The document is an ECFS product and endorsed by the CF Network in ERN LUNG and CF Europe.

Mycobacterium abscessus infections in lung transplant recipients: 15-year experience from a single institution

PURPOSE

To evaluate our institutional experience with Mycobacterium abscessus infections occurring in lung transplant recipients (LTR).

METHODS

We retrospectively reviewed our prospectively collected institutional adult lung transplant database from 2001 to 2015 to identify patients with M. abscessus or Mycobacterium chelonae/abscessus infection before or after transplantation. Untreated, colonized patients were excluded from the study. Electronic health records of nine out of 516 lung recipients (1.74%) with clinical infection were reviewed to determine outcomes.

RESULTS

Seven patients acquired the infection after transplantation. Indications for transplantation were: idiopathic pulmonary fibrosis (in 6), chronic obstructive pulmonary disease (in 2), and cystic fibrosis (in 1). Five patients (55.5%) underwent bilateral lung transplantation; one patient required bilateral re-transplantation for complications from infection. M. abscessus was isolated from the respiratory tract with a median time of 7.5 months (range: 3 days to 13 months) from transplantation. All patients were treated using a multidrug regimen, with durations ranging from 3 days to 12 months. Complications from infection included death in one patient, bronchial anastomotic dehiscence in one patient, delayed bronchial occlusions in two patients, and osteomyelitis of the knee in one patient. Median survival time from transplantation was 39 months (range: 11-96 months) and from the date of first positive culture was 58 months (range: 3-91 months). Five patients (55.5%) were cured but two had re-infections >1 year later.

CONCLUSIONS

Mycobacterium abscessus infection in LTR is rare and can lead to severe complications. Eradication is difficult and usually requires prolonged combination antibiotic therapy and occasionally surgical management.

Mycobacterium abscessus disease in lung transplant recipients: Diagnosis and management

Mycobacterium abscessus complex (MAbsC) disease in lung transplant recipients is increasingly being recognized as an important cause of graft function decline and suboptimal outcomes. Lung transplant recipients appear to be at the highest risk of MAbsC among solid organ transplant recipients, as they have more intense immunosuppression, and the organisms preferentially inhabit the lungs. MAbsC is the most resistant species of rapidly growing mycobacteria and difficult to treat, causing considerable mortality and morbidity in immunocompetent and immunosuppressed patients. Herein we describe the risk factors, epidemiology, clinical features, diagnostics, and treatment strategies of MAbsC in lung transplant candidates and recipients.

Mycobacterial Infections in Solid Organ and Hematopoietic Stem Cell Transplantation

Mycobacterial infections are uncommon in solid organ and hematopoietic stem cell transplant recipients but carry significant morbidity and mortality. Donor screening strategies for tuberculosis should be emphasized in high-risk populations. Both tuberculosis and nontuberculous mycobacterial infections can have pulmonary and extrapulmonary manifestations of infections. Recommended treatment regimens typically involve multiple drugs with significant adverse effects and drug interactions.

Recipient selection process and listing for lung transplantation

Lung transplantation remains the ultimate treatment option for selected patients with end-stage (cardio) pulmonary disease. Given the current organ shortage, it is without any doubt that careful selection of potential transplant candidates is essential as this may greatly influence survival after the procedure. In this paper, we will review the current guidelines for referral and listing of lung transplant candidates in general, and in more depth for the specific underlying diseases. Needless to state that these are not absolute guidelines, and that decisions depend upon center's activity, waiting list, etc. Therefore, every patient should be discussed with the transplant center before any definite decision is made to accept or decline a patient for lung transplantation.

Bacterial infections in patients with primary ciliary dyskinesia: Comparison with cystic fibrosis

Primary ciliary dyskinesia (PCD) is an autosomal recessive disorder associated with severely impaired mucociliary clearance caused by defects in ciliary structure and function. Although recurrent bacterial infection of the respiratory tract is one of the major clinical features of this disease, PCD airway microbiology is understudied. Despite the differences in pathophysiology, assumptions about respiratory tract infections in patients with PCD are often extrapolated from cystic fibrosis (CF) airway microbiology. This review aims to summarize the current understanding of bacterial infections in patients with PCD, including infections with Pseudomonas aeruginosa, Staphylococcus aureus, and Moraxella catarrhalis, as it relates to bacterial infections in patients with CF. Further, we will discuss current and potential future treatment strategies aimed at improving the care of patients with PCD suffering from recurring bacterial infections.

Selection of Resistance to Clarithromycin in Mycobacterium abscessus Subspecies

Mycobacterium abscessus is an emerging pathogen against which clarithromycin is the main drug used. Clinical failures are commonly observed and were first attributed to acquired mutations in rrl encoding 23S rRNA but were then attributed to the intrinsic production of the erm(41) 23S RNA methylase. Since strains of M. abscessus were recently distributed into subspecies and erm(41) sequevars, we investigated acquired clarithromycin resistance mechanisms in mutants selected in vitro from four representative strains. Mutants were sequenced for rrl, erm(41), whiB, rpIV, and rplD and studied for seven antibiotic MICs. For mutants obtained from strain M. abscessus subsp. abscessus erm(41) T28 sequevar and strain M. abscessus subsp. bolletii, which are both known to produce effective methylase, rrl was mutated in only 19% (4/21) and 32.5% (13/40) of mutants, respectively, at position 2058 (A2058C, A2058G) or position 2059 (A2059C, A2059G). No mutations were observed in any of the other genes studied, and resistance to other antibiotics (amikacin, cefoxitin, imipenem, tigecycline, linezolid, and ciprofloxacin) was mainly unchanged. For M. abscessus subsp. abscessus erm(41) C28 sequevar and M. abscessus subsp. massiliense, not producing effective methylase, 100% (26/26) and 97.5% (39/40) of mutants had rrl mutations at position 2058 (A2058C, A2058G, A2058T) or position 2059 (A2059C, A2059G). The remaining M. abscessus subsp. massiliense mutant showed an 18-bp repeat insertion in rpIV, encoding the L22 protein. Our results showed that acquisition of clarithromycin resistance is 100% mediated by structural 50S ribosomal subunit mutations for M. abscessus subsp. abscessus erm(41) C28 and M. abscessus subsp. massiliense, whereas it is less common for M. abscessus subsp. abscessus erm(41) T28 sequevar and M. abscessus subsp. bolletii, where other mechanisms may be responsible for failure.