Mycobacterium lentiflavum as an emerging causative agent of cervical lymphadenitis

State-of-the-art treatment strategies for nontuberculous mycobacteria infections

INTRODUCTION

Non-tuberculous Mycobacteria (NTM) are a group of organisms whose importance in medicine seems to be increasing in recent times. The increasing number of patients susceptible to these diseases make it necessary to expand our knowledge of therapeutic options and to explore future possibilities for the development of a therapeutic arsenal.

AREAS COVERED

In this review, the authors provide a brief introduction about the present importance of NTM and describe the present recommendations of the available guidelines for their treatment. They include a description of the future options for the management of these patients, especially focusing on new antibiotics. The authors also look at possibilities for future therapeutic options, such as antibiofilm strategies.

EXPERT OPINION

No actual changes have been made to the current recommendations for the management of most NTM infections (except perhaps the availability of nebulized amikacin). However, it is also true that we have increased the number of available antibiotic treatment options with good in vitro activity against NTM. The use of these drugs in selected cases could increase the therapeutic possibilities. However, some problems are still present, such as the knowledge of the actual meaning of a NTM isolate, and will probably be a key part of future research.

Epidemiology of Non-Tuberculous Mycobacteria isolated from clinical specimens in Madrid, Spain, from 2013 to 2017

The epidemiology of non-tuberculous mycobacteria (NTM) in Spain is largely unknown because systematic reporting is not compulsory. The aim of our study was to describe the frequency and diversity of NTM species in our region and their distribution according to the source sample, gender, and age of the patients. We performed a multicenter study of all NTM isolated in 24 public hospitals in Madrid from 2013 to 2017. A total of 6.923 mycobacteria were isolated: 4535 (65.5%) NTM, and 2.388 (34.5%) Mycobacterium tuberculosis complex (MTB). Overall, 61 different NTM species were identified. The most frequently isolated species were Mycobacterium avium complex (47.7%), M. lentiflavum (12.2%), M. gordonae (9.2%), M. fortuitum (8.9%), and M. abscessus (3.9%). Whereas MTB cases were stable during the study period, the number of NTM isolates increased considerably from 930 isolates in 2013 to 1012 in 2017; a sharp increase occurred in the last year. The rise in NTM isolates was mostly due to M. lentiflavum, M. kansasii, and M. abscessus mainly isolated from respiratory specimens in patients older than 60. The increase in isolation rate of NTM in our region is consistent with the increasing rates reported worldwide in the last decades. The rise in NTM isolates was mainly attributed to M. lentiflavum but it also should be noted the increasing of species with high pathogenic potential such as M. kansasii and M. abscessus.

Microbial pathogens in source and treated waters from drinking water treatment plants in the United States and implications for human health

An occurrence survey was conducted on selected pathogens in source and treated drinking water collected from 25 drinking water treatment plants (DWTPs) in the United States. Water samples were analyzed for the protozoa Giardia and Cryptosporidium (EPA Method 1623); the fungi Aspergillus fumigatus, Aspergillus niger and Aspergillus terreus (quantitative PCR [qPCR]); and the bacteria Legionella pneumophila (qPCR), Mycobacterium avium, M. avium subspecies paratuberculosis, and Mycobacterium intracellulare (qPCR and culture). Cryptosporidium and Giardia were detected in 25% and in 46% of the source water samples, respectively (treated waters were not tested). Aspergillus fumigatus was the most commonly detected fungus in source waters (48%) but none of the three fungi were detected in treated water. Legionella pneumophila was detected in 25% of the source water samples but in only 4% of treated water samples. M. avium and M. intracellulare were both detected in 25% of source water, while all three mycobacteria were detected in 36% of treated water samples. Five species of mycobacteria, Mycobacterium mucogenicum, Mycobacterium phocaicum, Mycobacterium triplex, Mycobacterium fortuitum, and Mycobacterium lentiflavum were cultured from treated water samples. Although these DWTPs represent a fraction of those in the U.S., the results suggest that many of these pathogens are widespread in source waters but that treatment is generally effective in reducing them to below detection limits. The one exception is the mycobacteria, which were commonly detected in treated water, even when not detected in source waters.

General Overview on Nontuberculous Mycobacteria, Biofilms, and Human Infection

Nontuberculous mycobacteria (NTM) are emergent pathogens whose importance in human health has been growing. After being regarded mainly as etiological agents of opportunist infections in HIV patients, they have also been recognized as etiological agents of several infections on immune-competent individuals and healthcare-associated infections. The environmental nature of NTM and their ability to assemble biofilms on different surfaces play a key role in their pathogenesis. Here, we review the clinical manifestations attributed to NTM giving particular importance to the role played by biofilm assembly.

Disseminated Mycobacterium lentiflavum responsible for hemophagocytic lymphohistocytosis in a man with a history of heart transplantation

Mycobacterium lentiflavum is a nontuberculous, slowly growing mycobacterium usually recognized as a contaminant. Here, we report a case of disseminated M. lentiflavum infection responsible for hemophagocytic lymphohistocytosis in a heart-transplanted man.

Comparison of Mycobacterium lentiflavum and Mycobacterium avium-intracellulare complex lymphadenitis

BACKGROUND

Mycobacterium lentiflavum is considered a rare pathogen causing nontuberculous mycobacterial (NTM) lymphadenitis.

METHODS

A multicenter, retrospective study was performed in immunocompetent children <14 years of age with microbiologically confirmed NTM lymphadenitis treated at 6 hospitals in Madrid, Spain, during 2000-2010. We compared children with M. lentiflavum and Mycobacterium avium-intracellulare complex infection.

RESULTS

Forty-five microbiologically confirmed NTM lymphadenitis patients were identified: 19 (45.2%) caused by M. avium-intracellulare complex, 17 (40.5%) by M. lentiflavum, 1 by both and 5 by other mycobacteria. Out of 17 M. lentiflavum cases, 14 were diagnosed in the past 5 years. Regarding M. lentiflavum cases, median age was 23 months. Submandibular nodes were the most frequently involved (76.5%), with multiple locations seen in 41% of the children and spontaneous drainage in 41% of them. Drug susceptibility tests were performed in 14 isolates and showed a complete susceptibility to clarithromycin and cycloserine, whereas 93% were resistant to rifampin, 33% to quinolones and full resistance to other tested antimycobacterial drugs was detected. All but 1 child required surgery and 11 were treated additionally with various drug combinations. Total resolution was achieved in 50% of children within 6 months.Compared with M. avium-intracellulare complex cases, children were younger and laterocervical nodes were significantly less frequently involved. No statistically significant differences were found related to clinical characteristics, treatment and outcome.

CONCLUSIONS

M. lentiflavum is an emerging pathogen producing NTM lymphadenitis in Madrid.

Epidemiology of cervico-facial pediatric lymphadenitis as a result of nontuberculous mycobacteria

Cervical lymphadenitis as a result of nontuberculous mycobacteria, otherwise known as scrofula, is a disease occurring almost exclusively in immunocompetent young children. The most frequent mycobacterial species responsible is Mycobacterium avium, but a large number of other species may also be involved. The epidemiology of such disease is revised here, and the impact of different species as causative agents of adenitis is also discussed.

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.

Mycobacterium lentiflavum in drinking water supplies, Australia

Humans may acquire infection from potable water.

Mycobacterium lentiflavum, a slow-growing nontuberculous mycobacterium, is a rare cause of human disease. It has been isolated from environmental samples worldwide. To assess the clinical significance of M. lentiflavum isolates reported to the Queensland Tuberculosis Control Centre, Australia, during 2001–2008, we explored the genotypic similarity and geographic relationship between isolates from humans and potable water in the Brisbane metropolitan area. A total of 47 isolates from 36 patients were reported; 4 patients had clinically significant disease. M. lentiflavum was cultured from 13 of 206 drinking water sites. These sites overlapped geographically with home addresses of the patients who had clinically significant disease. Automated repetitive sequence–based PCR genotyping showed a dominant environmental clone closely related to clinical strains. This finding suggests potable water as a possible source of M. lentiflavum infection in humans.

Clinical manifestations of nontuberculous mycobacteria infections

The isolation of nontuberculous mycobacteria (NTM) from clinical specimens has become very frequent in the last years. Such organisms are typically environmental and poorly pathogenic for humans; they can, however, be responsible for opportunistic diseases in subjects presenting with various predisposing conditions. Pulmonary infections are responsible for the most frequent disease caused by NTM, although the relevance of mycobacterioses involving other parts of the body is increasing. The risk of disseminated infections characterizing immunocompromised patients is well known, and those numbers are steadily rising. The lymph nodes, cutis and soft tissues, as well as bone and joints, are also important targets of NTM infection. The problems concerning the assessment of the clinical significance of NTM, along with a consideration of the more frequent NTM pathologies, are the major objectives of this review.

Nontuberculous mycobacterial infection in children: a prospective national study

BACKGROUND

The epidemiology and management of nontuberculous mycobacterial (NTM) infection in Australian children is unknown.

METHODS

From July 2004 to June 2007, clinicians identified children with NTM infection as part of a nationwide active surveillance network. Following notification, detailed data were collected.

RESULTS

From 192 reports, data were received on 153 cases (response rate: 79.7%). Of these, 102 met inclusion criteria. The median age was 2.9 years. Predisposing conditions were infrequent and included chronic respiratory disease (n = 12) and immunosuppression (n = 6). Lymphadenitis was the most frequent presentation (n = 68) with pulmonary and disseminated disease infrequent (n = 14 and 3, respectively). NTM was isolated in 68 cases with Mycobacterium avium-intracellulare complex most frequently isolated (33/68; 48.5%). Surgery was performed in 78 cases and 42 children were treated with antimycobacterial therapy. Twenty-five subjects received surgery and antimycobacterial therapy. Follow-up data were available for 77 children with recurrence observed in 18 cases. Complete excision was associated with a higher rate of treatment success when compared with all other therapies (OR: 9.48 [95% CI: 2.00-44.97], P = 0.001). Mycobacterium lentiflavum infection accounted for 4.4% of culture confirmed cases and had a lower rate of treatment success than other species (0% vs. 78.2%; P = 0.016).

CONCLUSIONS

The incidence of NTM infection in Australian children is 0.84 of 100,000 (95% CI: 0.68-1.02). Infection occurs most often in young children without predisposing conditions. Despite therapy, there was recurrence in 23.4% of cases.

Mycobacterium lentiflavum, an emerging pathogen?

Three cases of infection due to Mycobacterium lentiflavum, a recently described species characterized by multiple resistance to anti-mycobacterial drugs, are reported here. While one case simply adds to the number of cervical lynphadenitis reported in literature, the others concern the first isolations from pleural effusions, in a young boy with leukaemia and in an elderly patient with lung disease, respectively.