Nontuberculous mycobacterial meningitis: report of two cases and review

Mycobacterial biofilms: Understanding the genetic factors playing significant role in pathogenesis, resistance and diagnosis

Even though the genus Mycobacterium is a diverse group consisting of a majority of environmental bacteria known as non-tuberculous mycobacteria (NTM), it also contains some of the deadliest pathogens (Mycobacterium tuberculosis) in history associated with chronic disease called tuberculosis (TB). Formation of biofilm is one of the unique strategies employed by mycobacteria to enhance their ability to survive in hostile conditions. Biofilm formation by Mycobacterium species is an emerging area of research with significant implications for understanding its pathogenesis and treatment of related infections, specifically TB. This review provides an overview of the biofilm-forming abilities of different species of Mycobacterium and the genetic factors influencing biofilm formation with a detailed focus on M. tuberculosis. Biofilm-mediated resistance is a significant challenge as it can limit antibiotic penetration and promote the survival of dormant mycobacterial cells. Key genetic factors promoting biofilm formation have been explored such as the mmpL genes involved in lipid transport and cell wall integrity as well as the groEL gene essential for mature biofilm formation. Additionally, biofilm-mediated antibiotic resistance and pathogenesis highlighting the specific niches, sites of infection along with the possible mechanisms of biofilm dissemination have been discussed. Furthermore, drug targets within mycobacterial biofilm and their role as potential biomarkers in the development of rapid diagnostic tools have been highlighted. The review summarises the current understanding of the complex nature of Mycobacterium biofilm and its clinical implications, paving the way for advancements in the field of disease diagnosis, management and treatment against its multi-drug resistant species.

Difficulty in diagnosing intracranial infection caused by Mycobacterium avium in an AIDS patient: case report and review of the literature

BACKGROUND

Mycobacterium avium complex (MAC) is an uncommon clinical pathogen, especially in the central nervous system (CNS), and carries a poor prognosis. MAC infections commonly present as immune reconstitution disease (IRD) in HIV patients. Herein, we report a case of intracranial infection caused by MAC in an AIDS patient without disseminated MAC (DMAC) and immune reconstitution inflammatory syndrome (IRIS).

CASE PRESENTATION

A 31-year-old HIV-positive male presented us with progressively worsening CNS symptoms, and neuroimaging revealed ring-enhancing lesions. The intracranial lesions worsened after the empirical therapy for toxoplasma encephalitis and fungal infection. Due to the rapid progression of the disease, the patient died. Mycobacterium avium was the only pathogen in brain tissue after cultures and molecular biology tests.

CONCLUSION

MAC infection in CNS is challenging to diagnose in HIV patients. Our findings emphasize that obtaining tissue samples and applying molecular biology methods is essential to help diagnose the patient as soon as possible to receive adequate treatment.

Intracranial infection caused by Mycobacterium rhodesiae with specific imaging findings and good response to medication: a case report and literature review

Nontuberculous mycobacteria (NTM) are exceedingly rare etiological agents of intracranial infections. Among them, Mycobacterium rhodesiae stands out as an even less common pathogen. In this paper, we report the first documented case of a central nervous system (CNS) infection in humans caused by Mycobacterium rhodesiae, which has specific imaging findings and good response to the therapy by using Linezolid, Clarithromycin, and Minocycline. The diagnosis was facilitated by a comprehensive multimodal approach, incorporating multisite imaging, cerebrospinal fluid analysis via next-generation sequencing (NGS), and targeted genetic testing. Furthermore, this paper provides a derivation of the clinical characteristics observed in other documented instances of CNS infections attributable to NTM and based on a review of the current literature. Our experience contributes to the evidence that is needed to understand the full spectrum of NTM-related CNS pathologies and underscores the importance of a multidisciplinary diagnostic process in atypical presentations of intracranial infections.

Neurological manifestations of nontuberculous mycobacteria in adults: case series and review of the literature

Introduction

Nontuberculous mycobacteria (NTM) mediated infections are important to consider in cases with neuroinflammatory presentations. We aimed to characterize cases of NTM with neurological manifestations at the National Institutes of Health (NIH) Clinical Center and review the relevant literature.

Materials and methods

Between January 1995 and December 2020, six cases were identified. Records were reviewed for demographic, clinical, and radiological characteristics. A MEDLINE search found previously reported cases. Data were extracted, followed by statistical analysis to compare two groups [cases with slow-growing mycobacteria (SGM) vs. those with rapidly growing mycobacteria (RGM)] and evaluate for predictors of survival. NIH cases were evaluated for clinical and radiological characteristics. Cases from the literature were reviewed to determine the differences between SGM and RGM cases and to identify predictors of survival.

Results

Six cases from NIH were identified (age 41 ± 13, 83% male). Five cases were caused by SGM [Mycobacterium avium complex (MAC) n = 4; Mycobacterium haemophilum n = 1] and one due to RGM (Mycobacterium abscessus). Underlying immune disorders were identified only in the SGM cases [genetic (n = 2), HIV (n = 1), sarcoidosis (n = 1), and anti-interferon-gamma antibodies (n = 1)]. All cases were diagnosed using tissue analysis. A literature review found 81 reports on 125 cases (SGM n = 85, RGM n = 38, non-identified n = 2). No immune disorder was reported in 26 cases (21%). Within SGM cases, the most common underlying disease was HIV infection (n = 55, 65%), and seizures and focal lesions were more common. In RGM cases, the most common underlying condition was neurosurgical intervention or implants (55%), and headaches and meningeal signs were common. Tissue-based diagnosis was used more for SGM than RGM (39% vs. 13%, p = 0.04). Survival rates were similar in both groups (48% SGM and 55% in RGM). Factors associated with better survival were a solitary CNS lesion (OR 5.9, p = 0.01) and a diagnosis made by CSF sampling only (OR 9.9, p = 0.04).

Discussion

NTM infections cause diverse neurological manifestations, with some distinctions between SGM and RGM infections. Tissue sampling may be necessary to establish the diagnosis, and an effort should be made to identify an underlying immune disorder.

Metagenomic next-generation sequencing assistance in identifying Mycobacterium avium meningoencephalitis: A case report and literature review

Nontuberculous mycobacteria associated intracranial infection is a rare disease that mainly occurs in HIV-infected patients. The disease has a poor prognosis. The authors report a case of non-tuberculous mycobacterial meningoencephalitis in a non-AIDS patient, but long history of poorly controlled type 2 diabetes mellitus. A 55-year-old, right-handed, male patient presented with an 8-day history of fever, episodes of severe headache with signs of meningeal irritation. MRI showed hyperintensities/contrast enhancement in the visual pathways, basal ganglia sellar region and leptomeninges. No etiological diagnosis was reached until metagenomic next-generation sequencing (mNGS) was used, showing the presence of Mycobacterium avium. The patient was cured with aggressive antimycobacterial therapy. The authors discuss the clinical manifestations and drug therapy of nontuberculous mycobacteria-related intracranial infections by reviewing relevant literature. As meningoencephalitis by Mycobacterium avium has a high mortality an early diagnosis and appropriate therapeutic interventions are warranted. For this reason, the use of mNGS can be helpful to avoid therapeutic delay.

Epidemiology, clinical presentation, and predictors of outcome in nontuberculous mycobacterial central nervous system infection: a systematic review

BACKGROUND

CNS manifestations represent an emerging facet of NTM infection with significant mortality. Due to protean presentation and low index of suspicion, many cases are often treated erroneously as tubercular meningitis or fungal infections.

OBJECTIVES

Literature on NTM CNS disease is scarce, with most available data on pulmonary disease. This systematic review aimed to evaluate the epidemiology, clinical presentation, diagnostic modalities, and predictors of outcome in CNS NTM infection.

METHODS

The literature search was performed in major electronic databases (PubMed, Google Scholar, and Scopus) using keywords "CNS," "Central nervous system," "brain abscess," "meningitis," "spinal," "Nontuberculous mycobacteria," "NTM". All cases of CNS NTM infection reported between January 1980 and December 2022 were included.

RESULTS

A total of 77 studies (112 cases) were included in the final analysis. The mean age of all patients was 38 years, with most patients male (62.5%). Mycobacterium avium complex (MAC) was the most common aetiology, followed by M. fortuitum and M. abscessus (34.8%, 21.4% and 15.2%, respectively). The disseminated disease was found in 33% of cases. HIV (33.9%) and neurosurgical hardware (22.3%) were the common risk factors. Intracranial abscess (36.6%) and leptomeningeal enhancement (28%) were the most prevalent findings in neuroimaging. The overall case fatality rate was 37.5%. On multivariate analysis, male gender (adjusted OR 2.4, 95% CI 1.2-7.9) and HIV (adjusted OR 3.7, 95% CI 1.8-6.1) were the independent predictors of mortality). M. fortuitum infection was significantly associated with increased survival (adjusted OR 0.18, 95% CI (0.08-0.45), p value 0.012).

CONCLUSIONS

Current evidence shows the emerging role of rapid-grower NTM in CNS disease. Male gender and HIV positivity were associated with significant mortality, while M fortuitum carries favourable outcomes.

A Rare Case of Nontuberculous Mycobacterial Abscess Mimicking Brain Tumor in an Immunocompetent Patient

Nontuberculous mycobacteria (NTM) is a type of bacteria that typically infects the pulmonary system, and NTM-central nervous system (CNS) infection, which occurs in the brain, is a very rare disease. A 64-year-old female patient presented with seizures as the main symptom and was found to have a mass of less than 1 cm in the right temporal lobe with accompanying edema. Although diseases such as tumor metastasis and parasitic cyst were suspected, the patient underwent a surgical resection, and NTM-CNS infection with abscess was diagnosed through biopsy. Antibiotic treatment was initiated after surgery, and the patient has been followed up without any significant symptoms. In this report, we review a rare case of NTM-CNS infection and discuss the understanding and treatment of this disease.

Genetic Underpinnings of Carotenogenesis and Light-Induced Transcriptome Remodeling in the Opportunistic Pathogen Mycobacterium kansasii

Mycobacterium kansasii (Mk) causes opportunistic pulmonary infections with tuberculosis-like features. The bacterium is well known for its photochromogenicity, i.e., the production of carotenoid pigments in response to light. The genetics defining the photochromogenic phenotype of Mk has not been investigated and defined pigmentation mutants to facilitate studies on the role of carotenes in the bacterium's biology are not available thus far. In this study, we set out to identify genetic determinants involved in Mk photochromogenicity. We screened a library of ~150,000 transposon mutants for colonies with pigmentation abnormalities. The screen rendered a collection of ~200 mutants. Each of these mutants could be assigned to one of four distinct phenotypic groups. The insertion sites in the mutant collection clustered in three chromosomal regions. A combination of phenotypic analysis, sequence bioinformatics, and gene expression studies linked these regions to carotene biosynthesis, carotene degradation, and monounsaturated fatty acid biosynthesis. Furthermore, introduction of the identified carotenoid biosynthetic gene cluster into non-pigmented Mycobacterium smegmatis endowed the bacterium with photochromogenicity. The studies also led to identification of MarR-type and TetR/AcrR-type regulators controlling photochromogenicity and carotenoid breakdown, respectively. Lastly, the work presented also provides a first insight into the Mk transcriptome changes in response to light.

M. fortuitum-induced CNS-pathology: Deciphering the role of canonical Wnt signaling, blood brain barrier components and cytokines

Molecular underpinning of mycobacteria-induced CNS-pathology is not well understood. In the present study, zebrafish were infected with Mycobacterium fortuitum and the prognosis of CNS-pathogenesis studied. We observed M. fortuitum triggers extensive brain-pathology. Evans blue extravasation demonstrated compromised blood-brain barrier (BBB) integrity. Further, decreased expression in tight-junction (TJ) and adherens junction complex (AJC) genes were noted in infected brain. Wnt-signaling has emerged as a major player in host-mycobacterial immunity but its involvement/role in brain-infection is not well studied. Sustained expression of wnt2, wnt3a, fzd5, lrp5/6 and β-catenin, with concordant decline in degradation complex components axin, gsk3β and β-catenin regulator capn2a were observed. The surge in ifng1 and tnfa expression preceding il10 and il4 suggested cytokine-interplay critical in M. fortuitum-induced brain-pathology. Therefore, we suggest adult zebrafish as a viable model for studying CNS-pathology and using the same, conclude that M. fortuitum infection is associated with repressed TJ-AJC gene expression and compromised BBB permeability. Our results implicate Wnt/β-catenin pathway in M. fortuitum-induced CNS-pathology wherein Th1-type signals facilitate bacterial clearance and Th2-type signals prevent the disease sequel.

Clinical usefulness of metagenomic next-generation sequencing for the diagnosis of central nervous system infection in people living with HIV

OBJECTIVES

To evaluate the clinical utility of metagenomic next-generation sequencing (mNGS) for the diagnosis of central nervous system (CNS) infection in people living with human immunodeficiency virus (PLWH) in a real-world situation.

METHODS

Cerebrospinal fluid (CSF) was sent for mNGS for PLWH who tested negative on all conventional tests but were still suspected to have CNS infection. A retrospective analysis was undertaken of the results and the clinical effect of mNGS on this cohort. The final diagnosis was adjudicated by a panel discussion following hospital discharge when the results of all tests and patients' responses to the empiric therapy were available.

RESULTS

Eighty-eight eligible PLWH, including 51 (58%) patients suspected of encephalitis and 34 (46.7%) patients suspected of meningitis, were included in the analysis. Sixty-eight (77.3%) patients were diagnosed with CNS infection, of which 50 were based on the pathogens identified by mNGS. The most common disease missed by mNGS was clinically suspected tuberculous meningitis, followed by clinically suspected non-tuberculous mycobacterial meningitis. The results from mNGS led to modification of treatment in 21 (23.9%) patients, and increased confidence in continuation of original therapy in 30 (34.1%) patients. During hospitalization, two (2.3%) patients died and 66 (75%) patients improved.

CONCLUSIONS

mNGS of CSF is a useful tool for the diagnosis of CNS infection among PLWH. Further investigations are warranted to improve its sensitivity.

Transposon mutagenesis in Mycobacterium kansasii links a small RNA gene to colony morphology and biofilm formation and identifies 9,885 intragenic insertions that do not compromise colony outgrowth

Mycobacterium kansasii (Mk) is a resilient opportunistic human pathogen that causes tuberculosis‐like chronic pulmonary disease and mortality stemming from comorbidities and treatment failure. The standard treatment of Mk infections requires costly, long‐term, multidrug courses with adverse side effects. The emergence of drug‐resistant isolates further complicates the already challenging drug therapy regimens and threatens to compromise the future control of Mk infections. Despite the increasingly recognized global burden of Mk infections, the biology of this opportunistic pathogen remains essentially unexplored. In particular, studies reporting gene function or generation of defined mutants are scarce. Moreover, no transposon (Tn) mutagenesis tool has been validated for use in Mk, a situation limiting the repertoire of genetic approaches available to accelerate the dissection of gene function and the generation of gene knockout mutants in this poorly characterized pathogen. In this study, we validated the functionality of a powerful Tn mutagenesis tool in Mk and used this tool in conjunction with a forward genetic screen to establish a previously unrecognized role of a conserved mycobacterial small RNA gene of unknown function in colony morphology features and biofilm formation. We also combined Tn mutagenesis with next‐generation sequencing to identify 12,071 Tn insertions that do not compromise viability in vitro. Finally, we demonstrated the susceptibility of the Galleria mellonella larva to Mk, setting the stage for further exploration of this simple and economical infection model system to the study of this pathogen.

Unusual cause of progressively impaired cognitive function: Mycobacterium avium complex meningoencephalitis

Mycobacterium avium complex (MAC) is a rare cause of meningoencephalitis. Non-tuberculous mycobacterium meningoencephalitis including MAC meningoencephalitis is an important cause of rapidly progressive dementia. We present a case of MAC meningoencephalitis in an immunosuppressed woman who had progressively impaired cognitive function. An 83-year-old woman who had been taking glucocorticoid for myasthenia gravis developed cognitive dysfunction and visual hallucinations over a period of 2 weeks. Cerebrospinal fluid (CSF) findings were normal, but MAC was positive in CSF culture and M. avium and M. intracellulare were identified by PCR. She was treated with multiple antimycobacterial agents and her symptoms fully recovered. MAC meningoencephalitis is an unusual cause of progressively impaired cognitive function. The possibility of mycobacterial central nervous system infection cannot be excluded by normal CSF findings.

Central Nervous System Tuberculosis : Etiology, Clinical Manifestations and Neuroradiological Features

PURPOSE

As a result of multilateral migration and globalization in times of humanitarian crises, western countries face a possible increase in the incidence of central nervous system tuberculosis (CNS TB). The diagnosis of CNS TB is challenging and often delayed due to the manifold and often non-specific presentation of the disease. The aim of this review is to analyze and summarize imaging features and correlated clinical findings of CNS TB.

METHODS

The different manifestations of CNS TB are explained and illustrated by characteristic neuroradiological as well as neuropathological findings. An overview on diagnostic and therapeutic approaches is provided. For clarity, tables summarizing the lesion patterns, differential diagnoses and diagnostic hints are added.

RESULTS

The CNS TB can be manifested (1) diffuse as tuberculous meningitis (TBM), (2) localized as tuberculoma or (3) tuberculous abscess or (4) in extradural and intradural spinal infections. Information on clinical presentation, underlying pathology and the distinguishing features is demonstrated. The TBM is further described, which may lead to cranial nerve palsy, hydrocephalus and infarction due to associated arteritis of the basal perforators. The differential diagnoses are vast and include other infections, such as bacterial, viral or fungal meningoencephalitis, malignant causes or systemic inflammation with CNS. Complicating factors of diagnosis and treatment are HIV coinfection, multi-drug resistance and TB-associated immune reconstitution inflammatory syndrome (IRIS).

CONCLUSIONS

Neurologists and (neuro-)radiologists should be familiar with the neuroradiological presentation and the clinical course of CNS TB to ensure timely diagnosis and treatment.

Other Slow-Growing Nontuberculous Mycobacteria

The list of clinically important slow-growing nontuberculous mycobacteria (NTM) continues to expand as new species are identified and older ones are found to be pathogenic. Based on pigment production, the strains may be classified as photochromogenic, scotochromogenic, or unpigmented. Some of these organisms are not newly discovered but have heretofore been considered virtually nonpathogenic. Previously, many were regarded as contaminants when isolated from clinical specimens. Ubiquitous in nature, many NTM have been isolated from groundwater or tap water, soil, house dust, domestic and wild animals, and birds. Most infections result from inhalation or direct inoculation from environmental sources. They are not spread from person to person. The infections may be localized or disseminated. In most cases, the optimal regimen or duration of therapy has not been firmly established. The results of in vitro susceptibility testing may be used to select a therapeutic regimen. Many experts recommend clarithromycin with companion drugs such as rifampin and ethambutol for most, but not all, slowly growing species. Aminoglycosides, clofazimine, fluoroquinolones, linezolid, pyrazinamide, or trimethoprim-sulfamethoxazole also may be effective against some strains. Immunocompetent patients with clinically significant infections with NTM usually should receive 18 to 24 months of therapy. Infected immunocompromised patients, particularly those with disseminated infection, probably should receive therapy as long as their immune systems remain impaired. Some of the species discussed include Mycobacterium alsiense, M. celatum, M. gordonae, M. haemophilum, M. kyorinense, M. malmoense, M. simiae complex, M. szulgai, M. terrae complex, M. ulcerans, and M. xenopi.

HIV and mycobacteria

The importance of mycobacteria as opportunistic pathogens, particularly members of the M. avium complex (MAC), in patients with progressive HIV infection was recognized early in the AIDS epidemic. It took longer to appreciate the global impact and devastation that would result from the deadly synergy that exists between HIV and M. tuberculosis. This HIV/M. tuberculosis co-pandemic is ongoing and claiming millions of lives every year. In addition to MAC, a number of other non-tuberculous mycobacteria have been recognized as opportunistic pathogens in HIV-infected individuals; some of these are more commonly encountered (e.g., M. kansasii) than others (M. haemophilum and M. genevense). Finally, there are challenges to concomitantly treating the HIV and the infecting Mycobacterium species, because of antimicrobial resistance, therapeutic side-effects and the complex pharmacologic interactions of the antiretroviral and antimycobacterial multidrug therapy.

Rapidly Growing Mycobacteria

Rapidly growing mycobacteria (RGM) compose approximately one-half of the currently validated mycobacterial species and are divided into six major groups, including the Mycobacterium fortuitum group, M. chelonae/M. abscessus complex, M. smegmatis group, M. mucogenicum group, M. mageritense / M. wolinskyi , and the pigmented RGM. This review discusses each group and highlights the major types of infections associated with each group. Additionally, phenotypic and molecular laboratory identification methods, including gene sequencing, mass spectrometry, and the newly emerging whole-genome sequencing, are detailed, along with a discussion of the current antimicrobial susceptibility methods and patterns of the most common pathogenic species.

Zoonotic bacterial meningitis in human adults

OBJECTIVE

To describe the epidemiology, etiology, clinical characteristics, treatment, outcome, and prevention of zoonotic bacterial meningitis in human adults.

METHODS

We identified 16 zoonotic bacteria causing meningitis in adults.

RESULTS

Zoonotic bacterial meningitis is uncommon compared to bacterial meningitis caused by human pathogens, and the incidence has a strong regional distribution. Zoonotic bacterial meningitis is mainly associated with animal contact, consumption of animal products, and an immunocompromised state of the patient. In a high proportion of zoonotic bacterial meningitis cases, CSF analysis showed only a mildly elevated leukocyte count. The recommended antibiotic therapy differs per pathogen, and the overall mortality is low.

CONCLUSIONS

Zoonotic bacterial meningitis is uncommon but is associated with specific complications. The suspicion should be raised in patients with bacterial meningitis who have recreational or professional contact with animals and in patients living in regions endemic for specific zoonotic pathogens. An immunocompromised state is associated with a worse prognosis. Identification of risk factors and underlying disease is necessary to improve treatment.

A Novel Rapidly Growing Mycobacterium Species Causing an Abdominal Cerebrospinal Fluid Pseudocyst Infection

Nontuberculous mycobacteria (NTM) are a rare cause of ventriculoperitoneal shunt infections. We describe the isolation and identification of a novel, rapidly growing, nonpigmented NTM from an abdominal cerebrospinal fluid pseudocyst. The patient presented with fevers, nausea, and abdominal pain and clinically improved after shunt removal. NTM identification was performed by amplicon and whole-genome sequencing.

Disseminated mycobacteriosis manifesting as paraplegia in two Parma wallabies (Macropus parma) naturally exposed to Mycobacterium avium

Two captive female Parma wallabies (Macropus parma) died after a history of flaccid paraplegia. On postmortem examination, granulomatous and suppurative osteomyelitis involving the left ischium and the lumbosacral region, with meningeal extension at the cauda equina, and caseonecrotic mastitis were the most significant changes. Multiple small nodules in the liver and spleen, and an enlargement of some lymph nodes with central caseous necrosis were also observed. Microscopically, a disseminated granulomatous inflammation with numerous multinucleate giant cells was seen. Numerous acid-fast bacilli were detected in macrophages, in multinucleated giant cells, and free in the central necrosis and suppurative exudate. After culture, polymerase chain reaction assays were carried out to detect the 65-kDa heat shock protein (Hsp65) and insertion sequences (IS)1245 and IS900. The causative agent was identified as Mycobacterium avium subsp. avium.

Central nervous system infection with non-tuberculous mycobacteria: a report of that infection in two patients with AIDS

Meningitis caused by non-tuberculous mycobacteria (NTM) has a low incidence and is a rare form of NTM infection. In an increasing number of cases, however, disseminated mycobacterial infection is noted in acquired immune deficiency syndrome (AIDS). Described here are two patients with AIDS who were infected with NTM. Both patients eventually died, but one did receive anti-NTM treatment. Non-tuberculous mycobacterial meningitis must be suspected in patients with AIDS who present with prolonged fever and brain symptoms, and anti-NTM drugs should be promptly administered if necessary.

Other HIV-associated pneumonias

The incidence, mortality, and epidemiology of human immunodeficiency virus (HIV)-associated pulmonary infections have changed as a result of effective antiretroviral and prophylaxis antimicrobial therapy. The clinical presentation, radiographic abnormalities, and treatment of pneumonia from various uncommon pathogens in patients with AIDS can be different from those in immunocompetent patients. Advances in invasive and noninvasive testing and molecular biological techniques have improved the diagnosis and prognosis of pulmonary infections in patients infected with HIV. This review focuses on pulmonary infections from nontuberculosis mycobacteria, cytomegalovirus, fungi (aspergillosis, cryptococcosis, endemic fungi), and parasites (toxoplasmosis), and uncommon bacterial pneumonia (nocardiosis, rhodococcosis) in these patients.

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.

CNS infections caused by Mycobacterium abscessus complex: clinical features and antimicrobial susceptibilities of isolates

OBJECTIVES

CNS infections caused by non-tuberculous mycobacteria (NTM) are rare and only three cases of CNS infections due to Mycobacterium abscessus complex have been reported.

METHODS

We searched the Mycobacteriology Database of the National Taiwan University Hospital and identified patients with CNS infections due to NTM.

RESULTS

A total of 15 patients, namely 4 HIV-seropositive patients and 11 HIV-seronegative patients, with CNS infections caused by NTM were identified during 2000-10. All of the HIV-seropositive patients had disseminated Mycobacterium avium complex infections. Among the 11 HIV-seronegative patients, NTM CNS infections were due to M. abscessus complex in 8 patients, M. avium complex in 2 patients and Mycobacterium kansasii in 1 patient. All the six preserved M. abscessus complex isolates were confirmed to be Mycobacterium massiliense by erm(41) PCR and 23S rRNA gene sequence analysis. Among the eight patients with infections due to M. abscessus complex, three had otolaryngological diseases, four had received neurosurgery and one had disseminated disease. Five patients received surgical debridement or intracranial device removal and three patients died of M. abscessus complex CNS infection. Among the five patients who survived, all received clarithromycin-based combination therapy with a median duration of 12 months and four received surgical intervention. All six isolates available for drug susceptibility testing showed uniform susceptibility to clarithromycin and five were susceptible to amikacin.

CONCLUSIONS

Our study revealed that M. abscessus complex isolates, particularly M. massiliense, should be considered potential pathogens causing CNS infections. Long-duration clarithromycin-based combination therapy plus surgical intervention may provide the best chance of cure.

Disseminated Mycobacterium kansasii infection associated with skin lesions: a case report and comprehensive review of the literature

Mycobacteruim kansasii occasionally causes disseminated infection with poor outcome in immunocompromised patients. We report the first case of disseminated M. kansasii infection associated with multiple skin lesions in a 48-yr-old male with myelodysplastic syndrome. The patient continuously had taken glucocorticoid during 21 months and had multiple skin lesions developed before 9 months without complete resolution until admission. Skin and mediastinoscopic paratracheal lymph node (LN) biopsies showed necrotizing granuloma with many acid-fast bacilli. M. kansasii was cultured from skin, sputum, and paratracheal LNs. The patient had been treated successfully with isoniazid, rifampin, ethmabutol, and clarithromycin, but died due to small bowel obstruction. Our case emphasizes that chronic skin lesions can lead to severe, disseminated M. kansasii infection in an immunocompromised patient. All available cases of disseminated M. kansasii infection in non HIV-infected patients reported since 1953 are comprehensively reviewed.

Spectrum of CNS disease caused by rapidly growing mycobacteria

We present a case of a patient with chronic meningoencephalitis caused by Mycobacterium abscessus. We also summarise the clinical features and outcomes of cases of CNS infection caused by rapidly growing mycobacteria that have been described in the literature. Rapidly growing mycobacteria are notorious for causing skin and soft-tissue infections after trauma or surgery, pulmonary disease in patients with cystic fibrosis, and disseminated disease in immunocompromised patients. CNS infection with this organism is extremely rare. Patients usually present with subacute to chronic meningitis, neutrophilic pleocytosis, and have a history of trauma or neurosurgery. The smears are often negative for acid-fast organisms, but may show Gram-positive rods. Treatment requires a long course of two or more antibiotics that have the ability to penetrate the blood-brain barrier, and possibly of steroids as immunomodulatory agents, such as those used in tuberculous meningitis.

Report of two fatal cases of Mycobacterium mucogenicum central nervous system infection in immunocompetent patients

Neurological infections due to rapidly growing mycobacteria (RGM) have rarely been reported. We recently investigated two unrelated immunocompetent patients, one with community-acquired lymphocytic meningitis and the other with cerebral thrombophlebitis. Mycobacterium mucogenicum was isolated in pure culture and detected by PCR sequencing of cerebrospinal fluid samples. Both patients eventually died. The two isolates exhibited an overlapping antimicrobial susceptibility pattern. They were susceptible in vitro to tetracyclines, macrolides, quinolones, amikacin, imipenem, cefoxitin, and trimethoprim-sulfamethoxazole and resistant to ceftriaxone. They shared 100% 16S rRNA gene sequence similarity with M. mucogenicum ATCC 49650T over 1,482 bp. Their partial rpoB sequences shared 97.8% and 98.1% similarity with M. mucogenicum ATCC 49650T, suggesting that the two isolates were representative of two sequevars of M. mucogenicum species. This case report should make clinicians aware that M. mucogenicum, an RGM frequently isolated from tap water or from respiratory specimens and mostly without clinical significance, can even be encountered in the central nervous system of immunocompetent patients.

Multiple cerebral abscesses as a complication of Mycobacterium fortuitum infection

Mycobacterium fortuitum is a rapidly growing, nontuberculous mycobacteria that has rarely been associated with central nervous system impairment. We describe the case of a patient who developed multiple cerebral abscesses revealing Mycobacterium fortuitum infection. Brain biopsy specimens showed suppurative, noncaseating, granulomatous inflammation consisting of epithelioid histiocytes and multinucleated giant cells. All clinical signs and CT scan cerebral lesions disappeared after institution of appropriate antimycobacterial therapy.

Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria

The history, taxonomy, geographic distribution, clinical disease, and therapy of the pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria (RGM) are reviewed. Community-acquired disease and health care-associated disease are highlighted for each species. The latter grouping includes health care-associated outbreaks and pseudo-outbreaks as well as sporadic disease cases. Treatment recommendations for each species and type of disease are also described. Special emphasis is on the Mycobacterium fortuitum group, including M. fortuitum, M. peregrinum, and the unnamed third biovariant complex with its recent taxonomic changes and newly recognized species (including M. septicum, M. mageritense, and proposed species M. houstonense and M. bonickei). The clinical and taxonomic status of M. chelonae, M. abscessus, and M. mucogenicum is also detailed, along with that of the closely related new species, M. immunogenum. Additionally, newly recognized species, M. wolinskyi and M. goodii, as well as M. smegmatis sensu stricto, are included in a discussion of the M. smegmatis group. Laboratory diagnosis of RGM using phenotypic methods such as biochemical testing and high-performance liquid chromatography and molecular methods of diagnosis are also discussed. The latter includes PCR-restriction fragment length polymorphism analysis, hybridization, ribotyping, and sequence analysis. Susceptibility testing and antibiotic susceptibility patterns of the RGM are also annotated, along with the current recommendations from the National Committee for Clinical Laboratory Standards (NCCLS) for mycobacterial susceptibility testing.

Perspective on animal models: chronic intracellular infections

Systemic human disease caused by organisms of the Mycobacterium avium-Mycobacterium intracellulare complex (MAC) represent a chronic intracellular infection in human hosts who are usually immunocompromised. To develop improved treatment and prophylaxis, and to obtain a better understanding of pathogenesis, we studied the beige mouse (C57 beige(+)/beige(+)) challenged orally or intravenously with a human isolate that causes lethal disease in patients with AIDS (MAC 101, serovar 1). Encouraging anti-MAC studies in animals, as reviewed here, should provide the basis for considering human trials with a promising agent. The ability of an antimicrobial agent to achieve high intracellular concentrations has correlated with the in vivo activity of several specific compounds.

Invasion of the brain and chronic central nervous system infection after systemic Mycobacterium avium complex infection in mice

Central nervous system (CNS) infections caused by nontuberculous mycobacteria have been described previously, especially in patients with AIDS. To investigate specific aspects of the pathogenesis of this entity, C57BL bg(+)/bg(-) mice were infected intravenously with Mycobacterium avium, and cultures of blood and brain as well as histopathology examination of brain tissue were carried out at several time points up to 6 months after infection. Low-grade inflammatory changes with small aggregates of lymphocytes and macrophages as well as perivascular cuffing were seen early in the infection. A small number of bacteria could be observed in the parenchyma of the choroid plexus. Six months after infection, numerous bacteria were present within the foamy macrophage of the granulomatous lesions along the ventricle and meninges. None of the mice developed clinical signs of meningitis or encephalitis or even died spontaneously during the period of observation. Use of CD18(-/-) knockout mice indicated that transport of the bacterium within neutrophils or monocytes into the brain is unlikely. Mild chronic CNS infection developed in the mice during sustained systemic M. avium infection, similar to what has been reported in most human cases.

Disseminated infection due to rapidly growing mycobacteria in immunocompetent hosts presenting with chronic lymphadenopathy: a previously unrecognized clinical entity

Disseminated infection due to rapidly growing mycobacteria is uncommon and occurs mostly in immunocompromised patients. We report 16 cases of such infection with an unusual presentation seen at Srinagarind Hospital, a university hospital in northeastern Thailand. The clinical features were different from those in previous reports. All of the patients presented with chronic bilateral cervical lymphadenopathy. Twelve had mycobacterial involvement of other organs (sinuses, 6 patients; lungs, 4; liver, 4; spleen, 3; skin, 3; bone and joint, 2; and tonsils, 2). An interesting occurrence in 11 patients was 14 episodes of reactive skin manifestations (Sweet's syndrome, 9; generalized pustulosis and erythema nodosum, 2 each; and pustular psoriasis, 1). No identifiable predisposing factors, including human immunodeficiency disease, were found in these patients. However, 8 patients had 11 episodes of prior infection or coinfection with other opportunistic pathogens (salmonellosis, 4; penicilliosis, 3; pulmonary tuberculosis, 2; and melioidosis and cryptococcosis, 1 each). These findings suggest that cell-mediated immunity is defective in these patients.

Mycobacterium fortuitum meningitis associated with an epidural catheter: case report and a review of the literature

Mycobacterium fortuitum is a rapidly growing organism that has rarely been associated with meningitis. A patient developed M. fortuitum meningitis as the result of a permanent indwelling, contaminated, epidural catheter. Diagnosis and treatment of the disease are difficult in that clinical features may be indolent, and many antimicrobials with activity against M. fortuitum have minimal cerebrospinal fluid penetration. This patient was cured with an antibiotic regimen that consisted of doxycycline, ciprofloxacin, imipenem, and clarithromycin, and removal of the epidural catheter.