Mycobacterium triplex infection in a liver transplant patient

The clinical significance of Mycobacterium triplex

OBJECTIVES

Mycobacterium triplex is a slow-growing nontuberculous mycobacteria (NTM) and is a rare cause of human disease. The pathogenicity, natural history and spectrum of disease is unknown. The aim of this study was to review the clinical features, outcomes and drug susceptibility testing (DST) of all M. triplex isolates in Queensland, Australia to guide management of this rare NTM infection in the future.

METHODS

This retrospective study included all patients who isolated M. triplex in Queensland, Australia from the 1st January 2000 to 31st December 2016. Clinical information was obtained from medical records to determine the clinical significance of isolates, natural history of disease and treatment outcomes. DST was performed on 15 isolates.

RESULTS

Forty-three patients (21 male) had positive cultures for M. triplex. Thirty-nine patients had isolates from pulmonary specimens and 17 (43.6%) met the American Thoracic Society criteria for NTM lung disease. Six patients with pulmonary infection received antimicrobial therapy with 5 patients demonstrating treatment success. Four patients had localised extrapulmonary disease and were cured with surgical management ± antimicrobial therapy. DST suggests 93% of isolates are susceptible to macrolides.

CONCLUSION

This is the largest case series of M. triplex isolates and confirms it is a rare human pathogen. Extrapulmonary disease responded well to surgical management. Treatment of M. triplex pulmonary disease is challenging, and the optimal antimicrobial regimen is unknown. However, the DST data suggests macrolide resistance is rare and macrolides should be included in treatment regimens.

Mycobacterium triplex pulmonary disease in an immunocompetent host: A case report and literature review

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The report describes a rare case of pulmonary disease due to M. triplex.

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The pulmonary lesion was discovered as an incidental finding on chest X-ray.

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The organism was identified by housekeeping gene sequencing analysis.

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The patient had a history of tuberculosis & non-tuberculous mycobacterial infection.

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The patient was treated with antimicrobials and the lesion was cured.

Mycobacterium triplex (M. triplex) is a bacterial species that can cause severe pulmonary diseases. Despite its clinical importance, only a few cases of M. triplex infection have been reported. Here, we present a rare case of pulmonary disease due to M. triplex in an immunocompetent patient who showed abnormal findings on chest X-ray and computed tomography scans. In this patient, the bacterium was identified by DNA sequencing analysis of the 16S rRNA and hsp65 genes. The patient was successfully treated with the appropriate antimicrobial agents. To put this case into the context of the current literature, we also reviewed other case reports of M. triplex infection.

Non-tuberculous mycobacterial infections in solid organ transplant recipients: An update

Non-tuberculous mycobacteria are ubiquitous environmental organisms that are now increasingly recognized as important causes of clinical disease in solid organ transplant recipients. Risk factors of non-tuberculous mycobacteria infection are severe immunologic defects and structural abnormalities. Lung transplant recipients are at higher risk for non-tuberculous mycobacterial disease compared to recipients of other solid organs. The clinical presentation could be skin and soft tissue infection, osteoarticular disease, pleuropulmonary infection, bloodstream (including catheter-associated) infection, lymphadenitis, and disseminated or multi-organ disease. Management of non-tuberculous mycobacteria infection is complex due to the prolonged treatment course with multi-drug regimens that are anticipated to interact with immunosuppressive medications. This review article provides an update on infections due to non-tuberculous mycobacteria after solid organ transplantation, and discusses the epidemiology, risk factors, clinical presentation, and management.

First detection of Mycobacterium triplex in Latin America

In this study we describe the first isolation of Mycobacterium triplex in Latin America. This species causes infections in humans, with very few reports from around the world. We isolated two sputum specimens of a patient with a 6-year history of human immunodeficiency and tuberculosis treatment failure. All tests used confirmed M. triplex and the patient responded well to drug therapy for 18months.

Draft Genome Sequence of Mycobacterium triplex DSM 44626

We announce the draft genome sequence of Mycobacterium triplex strain DSM 44626, a nontuberculosis species responsible for opportunistic infections. The genome described here is composed of 6,382,840 bp, with a G+C content of 66.57%, and contains 5,988 protein-coding genes and 81 RNA genes.

Cervical Lymphadenitis by Mycobacterium triplex in an Immunocompetent Child: Case Report and Review

Mycobacterium triplex was first described in 1996. This nontuberculous Mycobacterium causes a severe pulmonary disease in immunocompromised patients but it can involve also healthy patients. A literature search was made on the PubMed database and it produced only few cases of children with cervical lymphadenitis due to this Mycobacterium Triplex. We are describing a case of M. triplex cervical lymphadenitis in an immunocompetent child.

Antimicrobial susceptibility testing, drug resistance mechanisms, and therapy of infections with nontuberculous mycobacteria

Within the past 10 years, treatment and diagnostic guidelines for nontuberculous mycobacteria have been recommended by the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA). Moreover, the Clinical and Laboratory Standards Institute (CLSI) has published and recently (in 2011) updated recommendations including suggested antimicrobial and susceptibility breakpoints. The CLSI has also recommended the broth microdilution method as the gold standard for laboratories performing antimicrobial susceptibility testing of nontuberculous mycobacteria. This article reviews the laboratory, diagnostic, and treatment guidelines together with established and probable drug resistance mechanisms of the nontuberculous mycobacteria.

Successful management of primary nontuberculous mycobacterial infection of hepatic allograft following orthotopic liver transplantation for hepatitis C

Nontuberculous mycobacteria are a rare cause of disease in solid organ and hematopoietic stem cell transplant recipients. The impact of mycobacterial infections in transplant recipients necessitates prompt diagnosis and early initiation of therapy. However, diagnosis remains difficult and there is a lack of specific recommendations for the choice of anti-mycobacterial drugs, duration of therapy, and monitoring of graft function as well as immunosuppression in these patients. Issues involved in the management are illustrated by an index case of hepatic allograft infection due to Mycobacterium avium complex.

Mycobacterium triplex pulmonary disease in immunocompetent host

Mycobacterium triplex, a recently described, potentially pathogenic species, caused disease primarily in immunocompromised patients. We report a case of pulmonary infection due to this mycobacterium in an immunocompetent patient and review the characteristics of two other cases. In our experience, Mycobacterium triplex pulmonary infection is unresponsive to antimycobacterial chemotherapy.

The new mycobacterial species—emerging or newly distinguished pathogens

Diseases due to nontuberculous mycobacteria are increasing in frequency, especially in patients with compromised immunity. A number of "new" mycobacterial species have been described in the last decade, largely as the result of the use of new tools to identify previously unrecognized mycobacteria found in the environment and in clinical specimens. This article reviews many of these potentially pathogenic organisms, summarizing what is known regarding their phenotypic and genotypic characterization, antimicrobial susceptibility, and clinical significance.

Nontuberculous mycobacterial infection in hematopoietic stem cell and solid organ transplant recipients

Nontuberculous mycobacteria (NTM) are ubiquitous environmental organisms. In immunocompetent hosts, they are a rare cause of disease. In immunocompromised hosts, disease due to NTM is well documented. Reports of NTM disease have increased in hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients. This increase may reflect increased numbers of transplants, intensification of immune suppressive regimens, prolonged survival of transplant recipients, and/or improved diagnostic techniques. The difficulty of diagnosis and the impact associated with infections due to NTM in HSCT and SOT recipients necessitates that, to ensure prompt diagnosis and early initiation of therapy, a high level of suspicion for NTM disease be maintained. The most common manifestations of NTM infection in SOT recipients include cutaneous and pleuropulmonary disease, and, in HSCT recipients, catheter-related infection. Skin and pulmonary lesions should be biopsied for histologic examination, special staining, and microbiologic cultures, including cultures for bacteria, Nocardia species, fungi, and mycobacteria. Mycobacterial infections associated with catheters may be documented by tunnel or blood (isolator) cultures. Susceptibility testing of mycobacterial isolates is an essential component of optimal care. The frequent isolation of NTM other than Mycobacterium avium complex (MAC) from transplant recipients limits the extrapolation of therapeutic data from human immunodeficiency virus-infected individuals to the population of transplant recipients. Issues involved in the management of NTM disease in transplant recipients are characterized by a case of disseminated infection due to Mycobacterium avium complex in a lung transplant recipient, with a review of the relevant literature.

Disseminated infection with a mycobacterium related to Mycobacterium triplex with central nervous system involvement associated with AIDS

We report on a case of disseminated infection with central nervous system involvement due to an atypical mycobacterium related to Mycobacterium triplex in a severely immunodepressed human immunodeficiency virus-infected man.

Impact of genotypic studies on mycobacterial taxonomy: the new mycobacteria of the 1990s

The advancement of genetic techniques has greatly boosted taxonomic studies in recent years. Within the genus Mycobacterium, 42 new species have been detected since 1990, most of which were grown from clinical samples. Along with species for which relatively large numbers of strains have been reported, some of the new species of mycobacteria have been detected rarely or even only once. From the phenotypic point of view, among the new taxa, chromogens exceed nonchromogens while the numbers of slowly and rapidly growing species are equivalent. Whereas conventional identification tests were usually inconclusive, an important role was played by lipid analyses and in particular by high-performance liquid chromatography. Genotypic investigations based on sequencing of 16S rRNA gene have certainly made the most important contribution. The investigation of genetic relatedness led to the redistribution of the species previously included in the classically known categories of slow and rapid growers into new groupings. Within slow growers, the intermediate branch related to Mycobacterium simiae and the cluster of organisms related to Mycobacterium terrae have been differentiated; among rapid growers, the group of thermotolerant mycobacteria has emerged. The majority of species are resistant to isoniazid and, to a lesser extent, to rifampin. Many of the new species of mycobacteria are potentially pathogenic, and there are numerous reports of their involvement in diseases. Apart from disseminated and localized diseases in immunocompromised patients, the most frequent infections in immunocompetent people involve the lungs, skin, and, in children, cervical lymph nodes. The awareness of such new mycobacteria, far from being a merely speculative exercise, is therefore important for clinicians and microbiologists.

Mycobacterium triplex pulmonary infection in an immunocompetent patient

We present the case of a 47-year-old immunocompetent patient with clinical evidence of pulmonary mycobacterial disease which was found to be due to Mycobacterium triplex. This novel organism is an uncommon, emerging, pathogen for which few reports of clinical infection exist in the medical literature.

Newly described or emerging human species of nontuberculous mycobacteria

The advent of molecular testing in the laboratory has brought about the recognition of multiple newly characterized mycobacterial species not previously recognizable with most standard techniques. Some of the species are nonpathogenic, but the majority may cause clinical disease. Each is likely to have its own biology, drug susceptibility pattern, and response to drug/surgical therapy. Thus, it is important to try to recognize these new species in the laboratory. A study of the phenotypic and genotypic characteristics of these new species also may help to elucidate the epidemiology and pathogenesis of these organisms. In addition, there are multiple emerging species of nontuberculous mycobacteria including M. ulcerans, M. haemophilum, M. xenopi, and M. malmoense. [table: see text] These species are being recognized increasingly as a cause of human disease and recovered within the laboratory. The clinician must learn about these new pathogens to recognize them clinically and assist the laboratory in their recovery.