Update on Nontuberculous Mycobacterial Infections in Solid Organ and Hematopoietic Stem Cell Transplant Recipients

Nontuberculous Mycobacterial Infections in Pediatric Solid Organ Transplant and Hematopoietic Cell Transplant Recipients

The diagnosis of nontuberculous mycobacterial infections is challenging in pediatric solid organ transplant and hematopoietic cell transplant recipients due to the absence of specific clinical manifestations, limitations of sampling, prolonged times for culture and identification, and difficulty discerning colonization from clinical disease. Treatment is dependent on the nontuberculous mycobacterial species, disease type, and pattern of drug resistance. Treatment of nontuberculous mycobacterial infections involves prolonged durations of therapy using multiple medications, which are limited by toxicities and drug-drug interactions.

Nontuberculous Mycobacterial Pulmonary Disease in the Immunocompromised Host

The immunocompromised host is at an increased risk for pulmonary and extrapulmonary NTM infections. Where data are available in these specific populations, increased mortality is observed with NTM disease. Prior to starting therapy for NTM disease, providers should ensure diagnostic criteria are met as treatment is long and often associated with significant side effects and toxicities. Treatment should involve 2 to 4 agents and be guided by cultures and antimicrobial susceptibilities. Drug interactions are important to consider, especially in those with HIV or transplant recipients. Whenever possible, immunosuppression should be reduced or changed.

Clinical characteristics of extrapulmonary nontuberculous mycobacteria infections in comparison with pulmonary infections: A single-center, retrospective study in Japan

INTRODUCTION

The prevalence of nontuberculous mycobacteria (NTM) infections is increasing worldwide. Although NTM can affect extrapulmonary organs, studies on the clinical characteristics of extrapulmonary NTM are rare.

METHODS

We retrospectively analyzed patients who were newly diagnosed with NTM infections at Hiroshima University Hospital between 2001 and 2021 to investigate species distribution, infected sites, and risk factors of extrapulmonary NTM compared to pulmonary NTM.

RESULTS

Of the 261 NTM infections, 9.6% and 90.4% had extrapulmonary and pulmonary NTM, respectively. The mean ages of patients with extrapulmonary and pulmonary NTM were 53.4 and 69.3 years, 64.0% and 42.8% were male, 36.0% and 9.3% received corticosteroids, 20.0% and 0% had acquired immune deficiency syndrome (AIDS), and 56.0% and 16.1% had any immunosuppressive conditions, respectively. Younger age, corticosteroid use, and AIDS were associated with extrapulmonary NTM. In pulmonary NTM, Mycobacterium avium complex (MAC) accounted for 86.4% of NTM species, followed by M. abscessus complex (4.2%), whereas in extrapulmonary NTM, M. abscessus complex, MAC, M. chelonae, and M. fortuitum accounted for 36.0%, 28.0%, 12.0%, and 8.0%, respectively. Compared to pulmonary NTM, extrapulmonary NTM were significantly more likely to be rapid-growing mycobacteria (RGM) (56.0% vs. 5.5%). The most common sites of infection were the skin and soft tissues (44.0%), followed by the blood (20.0%), tenosynovium, and lymph nodes (12.0%).

CONCLUSION

Younger age and immunosuppressive conditions are associated with extrapulmonary NTM, with a higher prevalence of RGM in extrapulmonary NTM than in pulmonary NTM. These results provide a better understanding of extrapulmonary NTM.

Mycobacterial infections in adults with haematological malignancies and haematopoietic stem cell transplants: guidelines from the 8th European Conference on Infections in Leukaemia

Mycobacterial infections, both tuberculosis and nontuberculous, are more common in patients with haematological malignancies and haematopoietic stem cell transplant recipients than in the general population-although these infections remain rare. Mycobacterial infections pose both diagnostic and therapeutic challenges. The management of mycobacterial infections is particularly complicated for patients in haematology because of the many drug-drug interactions between antimycobacterial drugs and haematological and immunosuppressive treatments. The management of mycobacterial infections must also consider the effect of delaying haematological management. We surveyed the management practices for latent tuberculosis infection (LTBI) in haematology centres in Europe. We then conducted a meticulous review of the literature on the epidemiology, diagnosis, and management of LTBI, tuberculosis, and nontuberculous mycobacterial infections among patients in haematology, and we formulated clinical guidelines according to standardised European Conference on Infections in Leukaemia (ECIL) methods. In this Review, we summarise the available literature and the recommendations of ECIL 8 for managing mycobacterial infections in patients with haematological malignancies.

Differences in plasma proteomes for active tuberculosis, latent tuberculosis and non-tuberculosis mycobacterial lung disease patients with and without ESAT-6/CFP10 stimulation

BACKGROUND

Tuberculosis (TB) is one of the world's most problematic infectious diseases. The pathogen Mycobacterium tuberculosis (Mtb) is contained by the immune system in people with latent TB infection (LTBI). No overt disease symptoms occur. The environmental and internal triggers leading to reactivation of TB are not well understood. Non-tuberculosis Mycobacteria (NTM) can also cause TB-like lung disease. Comparative analysis of blood plasma proteomes from subjects afflicted by these pathologies in an endemic setting may yield new differentiating biomarkers and insights into inflammatory and immunological responses to Mtb and NTM.

METHODS

Blood samples from 40 human subjects in a pastoral region of Ethiopia were treated with the ESAT-6/CFP-10 antigen cocktail to stimulate anti-Mtb and anti-NTM immune responses. In addition to those of active TB, LTBI, and NTM cohorts, samples from matched healthy control (HC) subjects were available. Following the generation of sample pools, proteomes were analyzed via LC-MS/MS. These experiments were also performed without antigen stimulation steps. Statistically significant differences using the Z-score method were determined and interpreted in the context of the proteins' functions and their contributions to biological pathways.

RESULTS

More than 200 proteins were identified from unstimulated and stimulated plasma samples (UPSs and SPSs, respectively). Thirty-four and 64 proteins were differentially abundant with statistical significance (P < 0.05; Benjamini-Hochberg correction with an FDR < 0.05) comparing UPS and SPS proteomic data of four groups, respectively. Bioinformatics analysis of such proteins via the Gene Ontology Resource was indicative of changes in cellular and metabolic processes, responses to stimuli, and biological regulations. The m7GpppN-mRNA hydrolase was increased in abundance in the LTBI group compared to HC subjects. Charged multivesicular body protein 4a and platelet factor-4 were increased in abundance in NTM as compared to HC and decreased in abundance in NTM as compared to active TB. C-reactive protein, α-1-acid glycoprotein 1, sialic acid-binding Ig-like lectin 16, and vitamin K-dependent protein S were also increased (P < 0.05; fold changes≥2) in SPSs and UPSs comparing active TB with LTBI and NTM cases. These three proteins, connected in a STRING functional network, contribute to the acute phase response and influence blood coagulation.

CONCLUSION

Plasma proteomes are different comparing LTBI, TB, NTM and HC cohorts. The changes are augmented following prior blood immune cell stimulation with the ESAT-6/CFP-10 antigen cocktail. The results encourage larger-cohort studies to identify specific biomarkers to diagnose NTM infection, LTBI, and to predict the risk of TB reactivation.

Nontuberculous mycobacterial bloodstream infections after allogeneic hematopoietic stem cell transplantation

Non-tuberculous mycobacteria (NTM) bacteremia following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is rare, and limited data exist. We described the features of NTM bacteremia following allo-HSCT recipients in our hospital with a comprehensive review of the literature. Among the four cases of NTM bacteremia after allo-HSCT recipients in our hospital, two were catheter-related bloodstream infections (CRBSI), one was disseminated, and one was an unknown source of infection. Based on our report and the past literature, the incidence rate of NTM bacteremia was 0.1-1.3%. CRBSI (57%) was more common than disseminated infection (29%). Most cases with CRBSI were caused by rapidly growing mycobacteria (88%) and showed good prognoses under appropriate antimicrobial therapies. In contrast, slowly growing mycobacteria (71%) was more common than rapidly growing mycobacteria in disseminated NTM bacteremia. Although disseminated NTM bacteremia can remain stable with appropriate long-term management, three out of seven cases died of multi-organ failure. Background immunodeficiency after allo-HSCT and transplant-related comorbidities may be attributable to subsequent poor prognosis.

Targeted therapies for autoimmune/idiopathic nonmalignant diseases: risk and management of opportunistic infections

INTRODUCTION

The management of patients affected by autoimmune/idiopathic diseases has been revolutionized by the development of targeted therapies (TT). However, the use of TT is complicated by several adverse events, like opportunistic infections (OIs). The potential of TT to predispose to OIs mainly depends on the site of action; nevertheless, such associations are far from being deterministic, because many factors could increase the infection risk.

AREAS COVERED

The impact on the infective risk of different TT used for autoimmune/idiopathic diseases is far from being completely understood. Indeed, many post-marketing reports documented severe or unexpected infections in patients treated with TT that did not emerge during registrative trials. In this review, the authors attempt to provide an easy and practical update about the 'infectious' safety of TT and examine the management strategies of OIs and other infections more frequently observed in the course of treatment with TT.

EXPERT OPINION

The authors suggest to precisely schedule the clinical management of these subjects, both to prevent and eventually treat promptly the TT-related infectious complications. A coordinated approach should be implemented from different medical specialties to improve the overall understanding of safety of TT and, in general, the management of opportunistic infections in immune-compromised hosts.

Granuloma in the explanted lungs: Infectious causes and impact on post-lung transplant mycobacterial infection

INTRODUCTION

The significance of granuloma in explanted lungs of lung transplant recipients (LTR) on the development of post-transplant mycobacterial infection is unclear.

METHODS

A retrospective review comparing LTRs and heart-lung transplant (H-LTR) recipients with granuloma in the explanted lungs between 2000 and 2012 (excluding those LTRs with granuloma due to sarcoidosis) and LTRs or H-LTRs without granuloma. Patients were followed for 2 years post-transplant.

RESULTS

A total of 144 LTRs and 4 H-LTRs with granulomas (75 necrotizing and 73 non-necrotizing) and a comparator cohort of 144 LTRs and 4 H-LTRs without granuloma were analyzed. In LTRs with granulomas, identification of infectious organisms was more common by histopathology (35 AFB and 22 fungal) compared to cultures (six NTM and seven fungal) taken around time of the transplant. LTRs with granulomas were more likely to have pre-transplant non-tuberculous mycobacteria (NTM) infection compared to LTRs without granuloma; P < .01. In the multivariate analysis, having granuloma or positive mycobacterial cultures at time of transplant were associated with increased risk of post-transplant mycobacterial infection (HR = 1.8 95% CI [1.024-3.154]; P = .041 and HR = 2.083 95% CI [1.011-4.292]; P = .047). Although there was a trend toward increase mycobacterial disease in those with granulomas P = .056, there was no difference in survival post-transplantation between those with or without granuloma in the explanted lung; P = .886.

CONCLUSION

The presence of granuloma in the explanted lungs of LTRs or positive mycobacterial cultures at time of transplant is associated with an increased risk of mycobacterial infection post-transplant.

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.

Management of Mycobacterium Other than Tuberculosis in Solid Organ Transplantation

Mycobacteria other than tuberculosis are important pathogens to consider in solid organ transplant recipients. Delay in recognition and treatment may incur significant morbidity and mortality. Management of mycobacteria other than tuberculosis requires a knowledge of treatment specific for each species and drug-drug interactions between antimicrobial and immunosuppressive drugs. Therapy in solid organ transplant can be prolonged and may require a reduction in immunosuppression to improve outcomes.

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.

Esophageal Mycobacterium avium-intracellulare infection in a bone marrow transplant patient: Case report and literature review

Mycobacterium avium-intracellulare complex (MAC) is the most common cause of nontuberculous mycobacterial (NTM) disease in humans. We report a case of esophageal MAC disease in a patient who had allogeneic bone marrow transplant for acute lymphoblastic leukemia. Although pulmonary MAC in immunocompromised host is not uncommon, there are only a few cases of NTM-associated esophageal mass reported. Our report and literature review highlight the importance of considering MAC in the differential diagnosis of dysphagia or odynophagia.

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.

A successful aggressive surgical and medical approach to pulmonary artery obstruction due to Mycobacterium abscessus infection post lung transplantation

Mycobacterium abscessus infection following lung transplantation has historically been associated with poor outcomes. We report a case of bilateral lung retransplantation complicated by obstruction of the right pulmonary artery secondary to M. abscessus mycotic aneurysm. Aggressive surgical management, including reconstruction of the right pulmonary artery, was undertaken with prolonged antimicrobial therapy. Thirty-six months later, antibiotics have been discontinued and the patient has stable soft tissue chest wall disease with good graft function. Mortality and morbidity associated with M. abscessus infection is considerable but this case illustrates that with aggressive early management, outcomes may be favorable.

Incidence and Risk Factors for Nontuberculous Mycobacterial Infection after Allogeneic Hematopoietic Cell Transplantation

Allogenic hematopoietic stem cell transplant (HCT) recipients are at risk of many infections. Nontuberculous mycobacteria (NTM) are increasingly recognized as clinically significant pathogens in this population. We investigated the incidence and risk factors for NTM infection after allogeneic HCT. This retrospective cohort study included all patients with allogeneic HCT at our institution during 2001 to 2013. Patients who developed significant NTM infection (NTM disease) were identified. Multivariable modeling was used to identify risk factors for NTM disease, and a risk score model was constructed to identify high-risk patients. Of 1097 allogeneic HCT patients, 45 (4.1%) had NTM isolated and 30 (2.7%) had NTM disease (28 [93.3%] exclusively pulmonary, 2 [6.7%] pulmonary plus another site). Incidence of NTM infection by competing risk analysis was 2.8% at 5 years (95% CI, 1.9% to 4.0%). The median time to diagnosis was 343 days (range, 19 to 1967). In Fine-Gray proportional hazards modeling, only global severity of chronic graft-versus-host disease (cGVHD) (HR, 1.99; 95% CI, 1.12 to 3.53; P = .019,) and cytomegalovirus (CMV) viremia (HR, 5.77; 95% CI, 1.71 to 19.45; P = .004) were significantly associated with NTM disease. Using these variables a risk score was calculated: 1 point for CMV viremia or moderate cGVHD and 2 points for severe cGVHD. The score divided patients into low risk (0 to 1 points, n = 820 [77.3%], 3-year NTM risk 1.2%), intermediate risk (2 points, n = 161 [15.4%], 3-year NTM risk 7.1%), and high risk (3 points, n = 56 [5.4%], 3-year NTM risk 14.3%). NTM disease after allogeneic HCT is common. Severe cGVHD and CMV viremia are associated with increased risk, permitting risk stratification.

Epidemiology and Outcomes of Nontuberculous Mycobacterial Infections in Solid Organ Transplant Recipients at a Midwestern Center

BACKGROUND

Nontuberculous mycobacterial (NTM) infections have the potential to affect outcomes in solid organ transplant (SOT) recipients.

METHODS

Retrospective cohort of adults who underwent SOT at a Midwestern hospital between January 1, 2004, and December 31, 2013. NTM-infected patients had at least 1 positive culture for NTM posttransplant. NTM disease was defined by 1) American Thoracic Society/Infectious Disease Society of America criteria for respiratory specimens or 2) NTM cultured from a sterile site with a compatible clinical syndrome. The remaining NTM infected patients were classified as colonized. Cox regression analysis was used to determine the association of NTM with mortality among lung transplant recipients.

RESULTS

Of 3338 SOT recipients, 50 (1.5%) had NTM infection during a median 1038 days (range, 165-3706) follow-up posttransplant. Forty-three patients (86%) with NTM infection were lung transplant recipients; 18 of 43 (41.8%) were treated for NTM and 6 (13.9%) met disease criteria. Isolation of the same species on multiple occasions was associated with treatment among the colonized lung transplant recipients (8/12 [67%] vs 3/25 [12%] who were not treated, P = 0.014). NTM infection was not associated with increased mortality in lung transplant recipients (9/43 [20.9%] in infected died versus 161/510 [31.6%] in uninfected, age-adjusted hazard ratio, 0.56; 95% confidence interval, 0.2-1.1; P = 0.091). Three of 6 lung transplant recipients with NTM disease died compared with 6 of 37 colonized (hazard ratio, 7.0; 95% confidence interval, 1.5-31.5; P = 0.003).

CONCLUSIONS

Among SOT patients, NTM were most frequently identified from lung transplant recipients. NTM infection was not associated with increased mortality, although NTM disease was associated with increased mortality compared with colonization in lung transplant recipients.

Disseminated Mycobacterium haemophilum infection in a renal transplant recipient

Opportunistic infections are a major concern in renal and transplant medicine. We present the case of a renal transplant recipient with a generalised Mycobacterium haemophilum infection after an increase in immunosuppressive therapy and treatment with a tumour necrosis factor-α (TNF-α) inhibitor. Infection involved skin and soft tissue, joints and bones, as well as the renal transplant with an interstitial nephritis. Rapid diagnosis using PCR and DNA sequencing allowed early appropriate treatment. Triple antibiotic therapy and reduction in immunosuppression resulted in a slow but sustained recovery. Immunosuppression causes severe opportunistic infections. TNF-α inhibitors are very effective and well tolerated but have an increased susceptibility to infections with mycobacteria. Mycobacterial infections represent a significant clinical risk to transplant recipients because of their aggressive clinical course and the need for complex toxic antibiotic treatments. In these patients, M. haemophilum is a cause of skin infections.

Mycobacterium abscessus Complex - a Particular Challenge in the Setting of Lung Transplantation

Mycobacterium abscessus complex is an emerging pathogen in lung transplant candidates and recipients. M. abscessus complex is widespread in the environment and can cause pulmonary, skin and soft tissue, and disseminated infection, particularly in lung transplant recipients. It is innately resistant to many antibiotics making it difficult to treat. Herein we describe the epidemiology, clinical manifestations, diagnosis and treatment of M. abscessus with an emphasis on lung transplant candidates and recipients. We also outline the areas where data are lacking and the areas where further research is urgently needed.

Specific Proteins in Nontuberculous Mycobacteria: New Potential Tools

Nontuberculous mycobacteria (NTM) have been isolated from water, soil, air, food, protozoa, plants, animals, and humans. Although most NTM are saprophytes, approximately one-third of NTM have been associated with human diseases. In this study, we did a comparative proteomic analysis among five NTM strains isolated from several sources. There were different numbers of protein spots from M. gordonae (1,264), M. nonchromogenicum type I (894), M. nonchromogenicum type II (935), M. peregrinum (806), and M. scrofulaceum/Mycobacterium mantenii (1,486) strains, respectively. We identified 141 proteins common to all strains and specific proteins to each NTM strain. A total of 23 proteins were selected for its identification. Two of the common proteins identified (short-chain dehydrogenase/reductase SDR and diguanylate cyclase) did not align with M. tuberculosis complex protein sequences, which suggest that these proteins are found only in the NTM strains. Some of the proteins identified as common to all strains can be used as markers of NTM exposure and for the development of new diagnostic tools. Additionally, the specific proteins to NTM strains identified may represent potential candidates for the diagnosis of diseases caused by these mycobacteria.

Nontuberculous mycobacteria infections in immunosuppressed hosts

Diseases and therapies that reduce cell-mediated immunity increase the risk of nontuberculous mycobacterial (NTM) disease. Extrapulmonary NTM disease, including disseminated, skin, and catheter-related disease, is more common in immunosuppressed than immunocompetent patients. Mycobacterium avium complex remains the most common cause of NTM infection, but rapid growers including Mycobacterium abscessus, Mycobacterium chelonae, and Mycobacterium fortuitum play an important role in skin and catheter-related infections. With the exception of antibiotic prophylaxis for AIDS patients, the prevention of NTM remains difficult. Management is complicated, involving restoration of immune function and removal of catheters in addition to treatment with species-specific antibiotics per current guidelines.

Role of therapeutic drug monitoring in pulmonary infections: use and potential for expanded use of dried blood spot samples

Respiratory tract infections are among the most common infections in men. We reviewed literature to document their pharmacological treatments, and the extent to which therapeutic drug monitoring (TDM) is needed during treatment. We subsequently examined potential use of dried blood spots as sample procedure for TDM. TDM was found to be an important component of clinical care for many (but not all) pulmonary infections. For gentamicin, linezolid, voriconazole and posaconazole dried blood spot methods and their use in TDM were already evident in literature. For glycopeptides, β-lactam antibiotics and fluoroquinolones it was determined that development of a dried blood spot (DBS) method could be useful. This review identifies specific antibiotics for which development of DBS methods could support the optimization of treatment of pulmonary infections.