High rates of infection and colonization by nontuberculous mycobacteria after allogeneic hematopoietic stem cell transplantation

Prevalence and Characteristics of Non-tuberculous Mycobacteria (NTM) Infection in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation: a Systematic Review and Meta-analysis

PURPOSE

Non-tuberculous mycobacteria (NTM) infections in hematopoietic stem cell transplantation (HSCT) recipients represent a diagnostic and therapeutic challenge. Here, we aimed to review and analyze current literature on incidence, clinical presentation, and outcome of NTM infection after allogeneic HSCT.

METHODS

We performed a systematic review and meta-analysis of available literature regarding NTM infection in children and adults receiving allogeneic HSCT.

RESULTS

We identified 56 articles eligible for the analysis. Among 15 studies, describing 15,798 allogeneic HSCT, we estimated a prevalence of 1.26% (95% CI 0.72, 1.93) of NTM after transplant. Analysis of 175 patients with NTM infection showed a median time of diagnosis of 318 days after HSCT, an increased prevalence in adults (82.9%), and a most frequent pulmonary involvement (44%). Comparison between children and adults revealed an earlier post-transplant disease onset (median 130 days vs 287 days) and most frequent non-pulmonary presentation in children. A vast heterogeneity of therapeutic approach reflected the lack of universal recommendations regarding drug combination and duration of therapy. Overall, NTM-related mortality accounted for 33% in this systematic review.

CONCLUSION

Although rare, NTM infections can complicate post-transplant course with a high mortality rate in children and adults. The lack of prospective studies and guidelines prevents identification of risk factors and therapeutic recommendations.

Nontuberculous mycobacterial infections in patients with hematologic malignancies and recipients of hematopoietic stem cell transplantation

BACKGROUND

The incidence of mycobacterial infections in patients with hematologic malignancies and hematopoietic stem cell transplant (HSCT) recipients is increasing, contributing to significant mortality and morbidity. This review explores the epidemiology, risk factors, clinical presentation, diagnosis, and treatment of nontuberculous mycobacteria (NTM) in this population.

METHODS

A literature search was performed using PubMed with keywords and MeSH terms pertaining to the topics of nontuberculous mycobacteria, hematologic malignancies, hematopoietic stem cell transplant, cellular therapies, chimeric antigen therapies, epidemiology, diagnosis, and treatment. Additionally, we examined the reference lists of the included articles to identify other pertinent studies.

RESULTS

Diagnosing mycobacterial disease among patients with hematologic disease and treatment-associated immunosuppressive conditions is challenging due to the lack of distinctive clinical, radiographic, and laboratory markers, as well as the atypical manifestations compared to immunocompetent patients. Treatment involves using a combination of antibiotics for extended durations, coupled with strategies to achieve source control and reduce immunosuppression when feasible. This is complicated by the absence of clear data correlating in-vitro drug susceptibility and clinical outcome for many antimicrobials use to treat NTM, adverse drug-drug interactions, and the frequent challenges related to poor medication tolerability and toxicities.

CONCLUSION

The rising incidence and corresponding clinical challenges of mycobacterial infections in this unique patient population necessitate a heightened awareness and familiarity of NTM disease by clinicians to achieve timely diagnosis and favorable treatment outcomes.

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.

Epidemiology of Lower Respiratory Tract Infections and Community-Acquired Respiratory Viruses in Patients with Bronchiolitis Obliterans Syndrome after Hematopoietic Cell Transplantation: A Retrospective Cohort Study

BACKGROUND

Bronchiolitis obliterans syndrome (BOS)-chronic graft-versus-host disease (cGVHD) affecting the lungs-is an uncommon complication of allogeneic hematopoietic cell transplant (HCT). The epidemiology and complications of lower respiratory tract infections (LRTIs) and community-acquired respiratory viruses (CARVs) in these patients are poorly understood.

OBJECTIVES

We aim to characterize the epidemiology of LRTIs in patients with BOS complicating HCT. We also aim to explore the association of LRTIs and CARV detection on lung function in BOS patients.

STUDY DESIGN

Adult patients with BOS at Stanford Health Care between January 2010 and December 2019 were included in this retrospective cohort study. LRTI diagnosis was based on combined clinical, microbiologic, and radiographic criteria, using consensus criteria where available.

RESULTS

Fifty-five patients with BOS were included. BOS was diagnosed at a median of 19.2 (IQR 12.5-24.7) months after HCT, and patients were followed for a median of 29.3 (IQR 9.9-53.2) months from BOS diagnosis. Twenty-two (40%) patients died after BOS diagnosis; 17 patients died from complications of cGVHD (including respiratory failure and infection) and 5 died from relapsed disease. Thirty-four (61.8%) patients developed at least one LRTI. Viral LRTIs were most common, occurring in 29 (52.7%) patients, primarily due to rhinovirus. Bacterial LRTIs-excluding Nocardia and non-tuberculous mycobacteria (NTM)-were the second most common, occurring in 21 (38.2%) patients, mostly due to Pseudomonas aeruginosa. Fungal LRTIs, NTM, and nocardiosis occurred in 14 (25.5%), 10 (18.2%), and 4 (7.3%) patients, respectively. Median time to development of the first LRTI after BOS diagnosis was 15.3 (4.7-44.7) months. Twenty-six (76.5%) of the 34 patients who developed LRTIs had infections due to more than one type of organism-fungi, viruses, Nocardia, NTM, and other bacteria-over the observation period. Patients with at least one LRTI had significantly lower forced expiratory volume in one second percent predicted (FEV1%) (37% vs. 53%, p = 0.0096) and diffusing capacity of carbon monoxide (DLCO) (45.5% predicted vs. 69% predicted, p = 0.0001). Patients with at least one LRTI trended toward lower overall survival (OS) (p = 0.0899) and higher non-relapse mortality (NRM) (p = 0.2707). Patients with a CARV detected or LRTI diagnosed after BOS-compared to those without any CARV detected or LRTI diagnosed-were more likely to have a sustained drop in FEV1% from baseline of at least 10% (21 [61.8%] versus 7 [33.3%]) and a sustained drop in FEV1% of at least 30% (12 [36.4%] versus 2 [9.5%]).

CONCLUSIONS

LRTIs are common in BOS and associated with lower FEV1%, lower DLCO, and a trend toward decreased OS and higher NRM. Patients with LRTIs or CARVs (even absent lower respiratory tract involvement) were more likely to have substantial declines in FEV1% over time than those without. The array of organisms-including P. aeruginosa, mold, Nocardia, NTM, and CARVs-seen in BOS reflects the unique pathophysiology of this form of cGVHD, involving both systemic immunodeficiency and structural lung disease. These patterns of LRTIs and their outcomes can be used to guide clinical decisions and inform future research.

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.

A clinical approach to respiratory disease in patients with hematological malignancy, with a focus on respiratory infection

Respiratory complications, in particular infections, are common in the setting of hematological malignancy and after hematopoetic stem cell transplant. The symptoms can be nonspecific; therefore, it can be difficult to identify and treat the cause. However, an understanding of the specific immune defect, clinical parameters such as speed of onset, and radiological findings, allows the logical diagnostic and treatment plan to be made. Radiological findings can include consolidation, nodules, and diffuse changes such as ground glass and tree-in-bud changes. Common infections that induce these symptoms include bacterial pneumonia, invasive fungal disease, Pneumocystis jirovecii and respiratory viruses. These infections must be differentiated from inflammatory complications that often require immune suppressive treatment. The diagnosis can be refined with the aid of investigations such as bronchoscopy, computed tomography (CT) guided lung biopsy, culture, and serological tests. This article gives a schema to approach patients with respiratory symptoms in this patient group; however, in the common scenario of a rapidly deteriorating patient, treatment often has to begin empirically, with the aim to de-escalate treatment subsequently after targeted investigations.

Pseudo-outbreak of Mycobacterium chimaera through aerators of hand-washing machines at a hematopoietic stem cell transplantation center

We identified a waterborne pseudo-outbreak of Mycobacterium chimaera in our stem cell transplantation center, which likely resulted from biofilm on the aerators of the handwashing machines in each patient’s room. Regular replacement of faucet parts can prevent biofilm formation and pseudo-outbreaks of M. chimaera through aerators.

Mycobacterium Avium Prosthetic Hip Infection on Abatacept Presenting as Fever of Unknown Origin

Non-tuberculous mycobacteria (NTM) are well-described pulmonary pathogens in patients with underlying lung disease. Extra-pulmonary infections with NTM are rare. We describe a prosthetic hip infection with Mycobacterium avium complex. Increased immunosuppressing medications and number of total joint replacements are expected to increase the prevalence of NTM infections in the future.

Tap water: A possible source of nontuberculous mycobacterial infection in patients with T cell deficiency

Five patients, all with severe T cell dysfunction, had invasive non-tuberculous mycobacteria (NTM) infections diagnosed over a 16 month period, with four meeting Centers for Disease Control and Prevention criteria for hospital-acquired infections. Testing of the hospitals tap water confirmed the presence of NTM. NTM are naturally present in water systems and present a threat to patients with lymphopenia; steps should be taken to avoid NTM exposure when caring for this patient population.

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.

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.

Laboratory Diagnosis of Infections in Cancer Patients: Challenges and Opportunities

Infections remain a significant cause of morbidity and mortality in cancer patients. The differential diagnosis for these patients is often wide, and the timely selection of the right clinical tests can have a significant impact on their survival. However, laboratory findings with current methodologies are often negative, challenging clinicians and laboratorians to continue the search for the responsible pathogen. Novel methodologies are providing increased sensitivity and rapid turnaround time to results but also challenging our interpretation of what is a clinically significant pathogen in cancer patients. This minireview provides an overview of the most common infections in cancer patients and discusses some of the challenges and opportunities for the clinical microbiologist supporting the care of cancer patients.

Health-related quality of life, comorbidities and mortality in pulmonary nontuberculous mycobacterial infections: A systematic review

Nontuberculous mycobacterial (NTM) infections are increasing in disease frequency worldwide. This systematic review examines health-related quality of life (HRQOL), comorbidities and mortality associated with pulmonary NTM disease. We searched MEDLINE, EMBASE, CINAHL, Scopus Life Sciences, conference proceedings and Google (earliest date available to February 2015) for primary studies. Eligible studies compared populations with and without pulmonary NTM disease in high-income jurisdictions. We excluded studies on HIV/AIDS. All languages were accepted. Two reviewers followed MOOSE and PRISMA reporting guidelines and independently appraised quality using STROBE. All studies were summarized qualitatively regardless of quality. Of 3193 citations screened, we included 17 studies mostly from Taiwan (n = 5) and the USA (n = 4). Two studies assessed HRQOL; one assessed comorbidities, 11 assessed mortality, and three assessed multiple outcomes. Populations with pulmonary NTM reported significantly worse or similar HRQOL than the general population, depending on the instruments used. Some suggested greater prevalence of having bronchiectasis (n = 2) and greater risk of developing pulmonary tuberculosis (n = 1). Most (n = 7) suggested no difference in mortality, although only one was age-matched and gender-matched to the general population. Four suggested NTM populations had higher mortality-two of which compared with the general population and were deemed of high quality, while two compared with non-NTM patients from hospital. High clinical heterogeneity in study design may explain discordant results. Bias assessments and controlling for confounding were carried out poorly. No consistent trends were observed although there is suggestion of an increased health burden from respiratory diseases and increased mortality associated with pulmonary NTM disease.

Mycobacterium avium intracellulare complex causing olecranon bursitis and prosthetic joint infection in an immunocompromised host

Case

A 73-year-old immunocompromised male presented with recurrent left elbow swelling due to Mycobacterium avium intracellulare complex (MAC) olecranon bursitis. 3 years after completing MAC treatment, he underwent right total knee arthroplasty (TKA). 1 year later, he developed TKA pain and swelling and was diagnosed with MAC prosthetic joint infection (PJI). He underwent TKA resection, reimplantation, and 12 months of anti-MAC therapy. This patient is the seventh case report of MAC olecranon bursitis and the third case report of MAC PJI. He is the only report of both MAC olecranon bursitis and PJI occurring in the same patient.

Informed consent

This patient was informed and agreed to the publication of this material.

A Case of Rapid Exacerbation of Pulmonary Mycobacterium Avium Complex Infection Mimicking Pulmonary Aspergillosis

We herein report a case of pulmonary Mycobacterium avium complex (MAC) infection with pulmonary multiple nodules and the "halo sign" on chest computed tomography (CT) in which the patient showed rapid exacerbation seven years after undergoing bone marrow transplantation (BMT). A 68-year-old Japanese female visited our hospital due to a productive cough and dyspnea. She had undergone allogeneic BMT for acute myelocytic leukemia and received both prednisolone (2 mg/day) and cyclosporine (30 mg/day). Chest CT demonstrated no abnormal findings on admission; however, multiple pulmonary nodules and the "halo sign" were detected three weeks later. Although a fungal infection was initially suspected, a bronchoscopic examination revealed pulmonary MAC infection. In the present case, pulmonary MAC infection exhibited rapid progression with unique CT findings. Physicians should consider MAC infection in the differential diagnosis in patients who receive BMT and/or immunosuppressive agents, even if the clinical and radiological findings are atypical of the disease.

Pneumonia in the neutropenic cancer patient

PURPOSE OF REVIEW

Pneumonia is the leading cause of death among neutropenic cancer patients, particularly those with acute leukaemia. Even with empiric therapy, case fatality rates of neutropenic pneumonias remain unacceptably high. However, recent advances in the management of neutropenic pneumonia offer hope for improved outcomes in the cancer setting. This review summarizes recent literature regarding the clinical presentation, microbiologic trends, diagnostic advances and therapeutic recommendations for cancer-related neutropenic pneumonia.

RECENT FINDINGS

Although neutropenic patients acquire pathogens both in community and nosocomial settings, patients' obligate healthcare exposures result in the frequent identification of multidrug-resistant bacterial organisms on conventional culture-based assessment of respiratory secretions. Modern molecular techniques, including expanded use of galactomannan testing, have further facilitated identification of fungal pathogens, allowing for aggressive interventions that appear to improve patient outcomes. Multiple interested societies have issued updated guidelines for antibiotic therapy of suspected neutropenic pneumonia. The benefit of antibiotic medications may be further enhanced by agents that promote host responses to infection.

SUMMARY

Neutropenic cancer patients have numerous potential causes for pulmonary infiltrates and clinical deterioration, with lower respiratory tract infections among the most deadly. Early clinical suspicion, diagnosis and intervention for neutropenic pneumonia provide cancer patients' best hope for survival.

Host susceptibility to non-tuberculous mycobacterial infections

Non-tuberculous mycobacteria cause a broad range of clinical disorders, from cutaneous infections, such as cervical or intrathoracic lymphadenitis in children, to disseminated infections at all ages. Recognition of the underlying immune defect is crucial for rational treatment, preventive care, family screening, and, in some cases, transplantation. So far, at least seven autosomal mutations (in IL12B, IL12RB1, ISG15, IFNGR1, IFNGR2, STAT1, and IRF8) and two X-linked mutations (in IKBKG and CYBB), mostly presenting in childhood, have been reported to confer susceptibility to disseminated non-tuberculous mycobacterial infection. GATA2 deficiency and anti-interferon γ autoantibodies also give rise to disseminated infection, typically in late childhood or adulthood. Furthermore, isolated pulmonary non-tuberculous mycobacterial infection has been increasing in prevalence in people without recognised immune dysfunction. In this Review, we discuss how to detect and differentiate host susceptibility factors underlying localised and systemic non-tuberculous mycobacterial infections.

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.

Cutaneous non-tuberculous mycobacterial infection in patients with chronic graft-versus-host disease: A case series

We report the first case series of allogeneic haematopoietic stem-cell transplant patients with graft versus host disease who developed cutaneous non-tuberculous mycobacteria infection. A multidisciplinary approach, reduction of immunosuppressive medications, combination of antibiotics, close skin surveillance and excision of suitable lesions are recommended in this specific subgroup.

Gastrointestinal pathology in transplant patients

The assessment of gastrointestinal (GI) specimens from transplant patients is complicated by the wide range of potentially rare pathologies that may be found in this clinical setting. Acute GI graft-versus-host disease (GvHD) is characterized by epithelial cell apoptosis, although there is increasing recognition that acute and/or chronic inflammation may also be present. By contrast, thus far there are no histological features known to be specific to chronic GI GvHD. Mycophenolate mofetil colitis may mimic both GvHD and inflammatory bowel disease, whereas both cytomegalovirus (CMV) and adenovirus infections can cause gland apoptosis. Post-transplant lymphoproliferative disorder should be considered if a Crohn's-like histological picture is seen, and granulomas in biopsies from umbilical cord blood recipients should raise a suspicion of cord colitis syndrome. Finally, the GI tract may be involved directly or indirectly by the disease that originally required haematopoietic stem cell or liver transplantation.

Infections caused by non-tuberculous mycobacteria in recipients of hematopoietic stem cell transplantation

Non-tuberculous mycobacteria (NTM) are acid-fast bacteria that are ubiquitous in the environment and can colonize soil, dust particles, water sources, and food supplies. They are divided into rapidly growing mycobacteria such as Mycobacterium fortuitum, Mycobacterium chelonae, and Mycobacterium abscessus as well as slowly growing species such as Mycobacterium avium, Mycobacterium kansasii, and Mycobacterium marinum. About 160 different species, which can cause community acquired and health care-associated infections, have been identified. NTM are becoming increasingly recognized in recipients of hematopoietic stem cell transplantation (HSCT) with incidence rates ranging between 0.4 and 10%. These infections are 50–600 times commoner in transplant recipients than in the general population and the time of onset ranges from day 31 to day 1055 post-transplant. They have been reported following various forms of HSCT. Several risk factors predispose to NTM infections in recipients of stem cell transplantation and these are related to the underlying medical condition and its treatment, the pre-transplant conditioning therapies as well as the transplant procedure and its complications. Clinically, NTM may present with: unexplained fever, lymphadenopathy, osteomyelitis, soft tissue and skin infections, central venous catheter infections, bacteremia, lung, and gastrointestinal tract involvement. However, disseminated infections are commonly encountered in severely immunocompromised individuals and bloodstream infections are almost always associated with catheter-related infections. It is usually difficult to differentiate colonization from true infection, thus, the threshold for starting therapy remains undetermined. Respiratory specimens such as sputum, pleural fluid, and bronchoalveolar lavage in addition to cultures of blood, bone, skin, and soft tissues are essential diagnostically. Susceptibility testing of mycobacterial isolates is a basic component of optimal care. Currently, there are no guidelines for the treatment of NTM infections in recipients of stem cell transplantation, but such infections have been successfully treated with surgical debridement, removal of infected or colonized indwelling intravascular devices, and administration of various combinations of antimicrobials. Monotherapy can be associated with development of drug resistance due to new genetic mutation. The accepted duration of treatment is 9 months in allogeneic stem cell transplantation and 6 months in autologous setting. Unfortunately, eradication of NTM infections may be impossible and their treatment is often complicated by adverse effects and interactions with other transplant-related medication.

An unusual lung mass post stem cell transplantation

We report a case of Mycobacterium kansasii presenting as an obstructing endobronchial mass in a patient post stem cell transplant. The patient had a complete clinical, microbiological, and radiological response to anti-tuberculous treatment. To our knowledge, this is the first case of M. kansasii presenting post transplant with an obstructing lung mass simulating relapse or post-transplant lymphoma.

Molecular methods for detection of invasive fungal infections and mycobacteria and their clinical significance in hematopoietic stem cell transplantation

Infection remains an important source of morbidity and mortality in patients who undergo hematopoietic stem cell transplantation (HSCT). In the immune reconstitution period after transplantation, HSCT recipients are most likely to have bacterial or fungal infections. Invasive fungal infections (IFIs) and mycobacterial infections (MBIs) are among the complications of HSCT, with high morbidity and mortality rates. Early diagnosis of both is crucial in order to manipulate the disease and to avoid fulminant outcomes. This chapter reviews the current knowledge on the molecular diagnosis of IFIs and MBIs in HSCT recipients, describing two different polymerase chain reaction (PCR)-based methods, one commercial (qPCR, Roche) and one in-house IS6110-based protocol.

Tuberculosis and hematopoietic stem cell transplant: Review of a difficult and often underestimated problem

Recipients of solid organ transplants (SOT) and stem cell transplants (SCT) constitute a group of patients at risk for tuberculosis (TB) development. The prevalence of active TB in patients undergoing SOT is higher than in patients undergoing SCT, probably due to the shorter period of immunosuppression in the latter. We reviewed the importance of SCT in individuals with hematological malignancies. Most TB cases occur in transplant patients by reactivation of latent infection after immunosuppression, most often within the first year after transplant, leading to graft loss and in some cases, death. Relevant variables to assess the risk of TB infection in a transplant recipient include the donor’s and recipient’s medical histories, imaging results, microbiology and tuberculin skin test (TST) and interferon-gamma release assays (IGRA). TST is routinely performed in the donor and recipient before transplantation. If TST is > 5 mm in the recipient or > 10 mm in the donor, it is necessary to exclude active TB (pulmonary and renal). Chemoprophylaxis is recommended in TST (+) recipients and in recipients with recent seroconversion, in donors with a history of untreated TB or in contact with an individual with active TB, if radiological images are suspicious and the IGRA is (+). The drug of choice is isoniazid. These topics are herewith reviewed.

Pulmonary disease caused by nontuberculous mycobacteria

The propensity of various nontuberculous mycobacteria to cause lung disease varies widely and is conditioned by host factors; infection is believed to occur from environmental sources. Nontuberculous mycobacteria pulmonary disease (PNTM) is increasing worldwide and Mycobacterium avium complex is the most common cause. PNTM usually occurs in one of three prototypical forms: hypersensitivity pneumonitis, cavitary tuberculosis-like disease or nodular bronchiectasis. PNTM has been linked in some patients to genetic variants of the cystic fibrosis transmembrane conductance regulator gene and a distinct patient phenotype. Interactions between PNTM and other comorbidities are also increasingly appreciated. Guidelines for diagnosis, emphasizing chest imaging and microbiology, have been published; speciation using molecular techniques is critical for accuracy and for treatment decisions. Clinical trials are lacking to inform treatment for many species and experience with M. avium complex and several others species serves as a guide instead. Use of multiple drugs for a period of at least 12 months following sputum conversion is the norm for most species. In vitro drug susceptibility results for many drugs may not correlate with clinical outcomes and such testing should be done on a selective basis.

Clinical utility of DNA amplification and sequencing to identify a strain of Mycobacterium avium in paraffin-embedded, formalin-fixed biopsies from an immunosuppressed child

Nontuberculous mycobacterial (NTM) infections are serious, though rare, in patients with severe combined immunodeficiency who have received bone marrow transplants. A 5-year-old female patient underwent stem cell/bone marrow transplant with disseminated NTM. Real-time polymerase chain reaction (PCR) using a fluorescence resonance energy transfer (FRET) probe for detection and identification of NTM was performed. The FRET-based real-time PCR assay amplified mycobacterial DNA, and the postamplification melt curve analysis classified the organism as a NTM. The pyrosequence of the hypervariable region A definitively identified the infecting organism as Mycobacterium avium. Real-time PCR along with melt curve analysis and pyrosequencing provides faster, definitive identification of mycobacteria, as compared to bacterial culture. In this case report, we emphasize the importance of utilizing molecular means for fast and accurate diagnosis.

Clinical manifestations, diagnosis, and treatment of Mycobacterium haemophilum infections

Mycobacterium haemophilum is a slowly growing acid-fast bacillus (AFB) belonging to the group of nontuberculous mycobacteria (NTM) frequently found in environmental habitats, which can colonize and occasionally infect humans and animals. Several findings suggest that water reservoirs are a likely source of M. haemophilum infections. M. haemophilum causes mainly ulcerating skin infections and arthritis in persons who are severely immunocompromised. Disseminated and pulmonary infections occasionally occur. The second at-risk group is otherwise healthy children, who typically develop cervical and perihilar lymphadenitis. A full diagnostic regimen for the optimal detection of M. haemophilum includes acid-fast staining, culturing at two temperatures with iron-supplemented media, and molecular detection. The most preferable molecular assay is a real-time PCR targeting an M. haemophilum-specific internal transcribed spacer (ITS), but another approach is the application of a generic PCR for a mycobacterium-specific fragment with subsequent sequencing to identify M. haemophilum. No standard treatment guidelines are available, but published literature agrees that immunocompromised patients should be treated with multiple antibiotics, tailored to the disease presentation and underlying degree of immune suppression. The outcome of M. haemophilum cervicofacial lymphadenitis in immunocompetent patients favors surgical intervention rather than antibiotic treatment.

[Diagnosis and treatment of atypical mycobacterial infections of the respiratory tract]

INTRODUCTION

Non tuberculous mycobacteria (NTM), unlike tuberculous mycobacteria, are not strictly human pathogens. The diagnosis of infection and the choice of treatment remain difficult.

BACKGROUND

Evidence of a NTM in a pulmonary sample is not synonymous with infection. The diagnosis depends on the association of clinical, radiological and microbiological factors. If a NTM is isolated from a respiratory sample, the probability of infection depends on the species. The main NTMs responsible for pulmonary infection in France are Mycobacterium avium intracellulare, Mycobacterium xenopi, Mycobacterium kansasi and Mycobacterium abscessus. Their management is difficult and poorly understood. Treatment is well established for M. avium intracellulare and M. kansasii, with combinations of clarithromycin-rifampicin-ethambutol and isoniazid-rifampicin-ethambutol respectively. For M. xenopi, the optimal treatment is not known and a combination of clarithromycin-rifampicin-ethambutol, with moxifloxacin as an alternative, is currently recommended. In general, treatment is prolonged and often associated with problems of tolerance.

VIEWPOINT AND CONCLUSION

The management of NTM infection, taking into account of the increase in patients "at risk", is an important issue. Further studies are needed to improve the criteria for infection and to find the optimal therapeutic combinations.

Disseminated Mycobacterium marinum infection in a hematopoietic stem cell transplant recipient

Mycobacterium marinum is a photochromogenic mycobacterium that is ubiquitous in the aquatic environment. In the general population, exposure to aquaria is the most common cause of M. marinum infection. Known as "swimmer's granuloma" or "fish tank granuloma," M. marinum is an occupational hazard for aquarium cleaners and fishermen. There are several reports in the literature of M. marinum infection in immunocompromised hosts, including those with solid organ transplants, but none in patients who have received stem cell transplants (SCTs). To our knowledge, this is a first report of disseminated M. marinum infection in an SCT recipient who continued to develop new skin lesions even after months of targeted therapy. The implications are that elderly patients who receive T-cell-depleted SCTs may be at prolonged risk for pathogens dependent on cellular immunity, and the presentation of illness with such pathogens may be more severe and widely disseminated than might otherwise be expected.

Mycobacterial infections in adult patients with hematological malignancy

We retrospectively analyzed the clinical and microbiological characteristics of adult patients with hematological malignancy and nontuberculous mycobacteria (NTM) infections from 2001 to 2010. During the study period, 50 patients with hematological malignancy and tuberculosis (TB) were also evaluated. Among 2,846 patients with hematological malignancy, 34 (1.2%) patients had NTM infections. Mycobacterium avium-intracellulare complex (13 patients, 38%) was the most commonly isolated species, followed by M. abscessus (21%), M. fortuitum (18%), and M. kansasii (18%). Twenty-six patients had pulmonary NTM infection and eight patients had disseminated disease. Neutropenia was more frequently encountered among patients with disseminated NTM disease (p = 0.007) at diagnosis than among patients with pulmonary disease only. Twenty-five (74%) patients received adequate initial antibiotic treatment. Five of the 34 patients died within 30 days after diagnosis. Cox regression multivariate analysis showed that chronic kidney disease (p = 0.017) and neutropenia at diagnosis (p = 0.032) were independent prognostic factors of NTM infection in patients with hematological malignancy. Patients with NTM infection had higher absolute neutrophil counts at diagnosis (p = 0.003) and a higher 30-day mortality rate (15% vs. 2%, p = 0.025) than TB patients. Hematological patients with chronic kidney disease and febrile neutropenia who developed NTM infection had significant worse prognosis than patients with TB infection.

Non-tuberculous mycobacterial infection localized in small intestine developing after allogeneic bone marrow transplantation

A 33-year-old man with myelodysplastic/myeloproliferative disease underwent allogeneic bone marrow transplantation. Around day 80 post-transplant, he complained of abdominal pain and diarrhea. Colonoscopy and esophagogastroduodenoscopy findings were unremarkable. Double-balloon enteroscopy revealed atrophic villi and mild erosions localized in the small intestine. Histological examination revealed marked proliferation of histiocytes with numerous acid-fast bacilli in their cytoplasm. The specific polymerase chain reaction for Mycobacterium tuberculosis was negative, and a diagnosis of intestinal non-tuberculous mycobacteria (NTM) was made. Physicians should recognize that NTM infection is one of the gastrointestinal infectious complications in immunocompromised patients such as bone marrow transplant recipients, and could localize in the small intestine.

Nontuberculous mycobacteria infections in immunocompromised patients: single institution experience

Disseminated infection due to nontuberculous Mycobacterium (NTM) species is rare in pediatrics. Here we report 6 infections affecting 5 patients at a single institution in an immunocompromised population of pediatric oncology and stem cell transplant recipients. The patients presented within a 1-year period with catheter-associated bacteremia. New pulmonary nodules were noted in 4 of the 5 patients. All of the infections were due to rapidly growing NTM. Patients were successfully treated with removal of the infected catheter and combination antibiotic therapy. There are currently no consensus guidelines for treatment of NTM infections in this population, and a therapeutic approach is presented here.

[Mycobacterium kansasii infection after liver transplantation]

Infections are one of the leading causes of morbidity and mortality in solid organ transplant recipients because of treatment with immunosuppressive agents. Infections due to nontuberculous mycobacteria (NTM) are infrequent but may be a major cause of morbidity. Treatment is associated with therapeutic limitations due to drug interactions with immunosuppressive agents and enhanced toxicity. Treatment of NTM infection most commonly involves surgery, reducing the doses of immunosuppressive medications and/or therapy with antimycobacterial medications The American Thoracic Society recommends isoniazid, rifampicin, and ethambutol. The current duration for treatment of pulmonary disease caused by Mycobacterium kansasii is 18 months. We describe the case of an immunosuppressed liver transplant recipient with poor outcome due to acute cholangitis who also developed concomitant infection with an uncommon organism, M. kansasii, in the late posttransplantation period.

Mycobacterium chelonae necrotizing pneumonia after allogeneic hematopoietic stem cell transplant: report of clinical response to treatment with tigecycline

We present a case of progressive Mycobacterium chelonae ssp. chelonae necrotizing pneumonia after hematopoietic stem cell transplantation (HSCT) in the presence of chronic graft-versus-host disease. The patient failed to respond to standard combination therapy with multiple agents and developed resistance to most drugs over the course of treatment. Tigecycline, a new glycylcycline antimicrobial agent with in vitro activity against M. chelonae, was then used with a clinical response to treatment. To our knowledge, this is the first reported case demonstrating tigecycline to have a degree of clinical effectiveness to treat refractory pulmonary infection with M. chelonae in an HSCT recipient.