Mycobacterium simiae cervical lymphadenitis

Draft Genome Sequence of Mycobacterium simiae, a Potential Pathogen Isolated from the Normal Human Oral Cavity

We report the draft genome sequence of Mycobacterium simiae, a slowly growing nontuberculous mycobacterium (NTM) isolated from a mouthwash sample of a healthy person. This genome of 6,603,693 bp exhibited a 66.13% GC content and 6,391 genes with 6,257 coding sequences, 3 rRNAs, and 78 tRNAs.

We report the draft genome sequence of Mycobacterium simiae, a slowly growing nontuberculous mycobacterium (NTM) isolated from a mouthwash sample of a healthy person. This genome of 6,603,693 bp exhibited a 66.13% GC content and 6,391 genes with 6,257 coding sequences, 3 rRNAs, and 78 tRNAs.

Disseminated Mycobacterium simiae infection in a patient with adult-onset immunodeficiency due to anti-interferon-gamma antibodies - a case report

Background

Mycobacterial species other than Mycobacterium tuberculosis and Mycobacterium leprae are generally free-living organisms and Mycobacterium simiae is one of the slowest growing Non-tuberculous mycobacteria. This is the first case report of Mycobacterium simiae infection in Sri Lanka and only very few cases with extrapulmonary manifestation reported in the literature.

Case presentation

A 24-year-old, previously healthy Sri Lankan male presented with generalized lymphadenopathy with discharging sinuses, evening pyrexia, weight loss, poor appetite and splenomegaly. Lymph node biopsies showed sheets of macrophages packed with organisms in the absence of granulomata. Ziehl Neelsen, Wade Fite and Giemsa stains revealed numerous red coloured acid-fast bacilli within foamy histiocytes. Slit skin smear for leprosy was negative and tuberculosis, fungal and bacterial cultures of the lymph node and bone marrow did not reveal any growth. Later he developed watery diarrhea and colonoscopy revealed multiple small polyps and ulcers throughout the colon extending up to the ileum, Which was confirmed to be due to cytomegalovirus confirmed by PCR and successfully treated with ganciclovir. Positron emission tomography scan guided biopsies of the gut and lymph nodes confirmed presence of mycobacterial spindle cell pseudo-tumours and PCR assays revealed positive HSP65. The culture grew Mycobacterium Simiae. Flow cytometry analysis on patient’s blood showed extremely low T and B cell counts and immunofixation revealed low immunoglobulin levels. His condition was later diagnosed as adult onset immunodeficiency due to anti- interferon – gamma autoantibodies. He was initially commenced on empirical anti-TB treatment with atypical mycobacterial coverage. He is currently on a combination of daily clarithromycin, ciprofloxacin, linezolid with monthly 2 g/kg/intravenous immunoglobulin to which, he had a remarkable clinical response with complete resolution of lymphadenopathy and healing of sinuses.

Conclusions

This infection is considered to be restricted to certain geographic areas such as mainly Iran, Cuba, Israel and Arizona and this is the first case report from Sri lanka. Even though the infection is mostly seen in the elderly patients, our patient was only 24 years old. In the literature pulmonary involvement was common presentation, but in this case the patient had generalized lymphadenopathy and colonic involvement without pulmonary involvement.

Clinical, Radiological, and Microbiological Characteristics of Mycobacterium simiae Infection in 97 Patients

Mycobacterium simiae is a rare species of slow-growing nontuberculous mycobacteria (NTM). From 2002 to 2017, we conducted a retrospective study that included all patients with NTM-positive respiratory samples detected in two university hospitals of the French overseas department of Reunion Island. We recorded the prevalence of M. simiae in this cohort, as well as the clinical, radiological, and microbiological features of patients with at least 1 sample positive for M. simiae In our cohort, 97 patients (15.1%) were positive for M. simiae Twenty-one patients (21.6%) met the American Thoracic Society (ATS) criteria for infection. M. simiae infection was associated with bronchiectasis, micronodular lesions, and weight loss. Antibiotic susceptibility testing was performed for 60 patients, and the isolates were found to have low susceptibility to antibiotics, except for amikacin, fluoroquinolones, and clarithromycin. Treatment failed for 4 of the 8 patients treated for M. simiae infection. Here, we describe a specific cluster corresponding to a large cohort of patients with M. simiae, a rare nontuberculous mycobacterium associated with low pathogenicity and poor susceptibility to antibiotics.

Computed Tomography Findings of Pulmonary Mycobacterium simiae Infection

Nontuberculous mycobacterial (NTM) pulmonary infections can be quite similar to tuberculosis, both clinically and radiologically. However, the treatment protocol is not similar. Mycobacterium simiae is a rare cause of NTM pulmonary infection. Herein, we aimed to evaluate and compare the computed tomography (CT) scan findings of M. simiae infection in lungs. For this reason, thirty-four patients (n = 34) with M. simiae lung infection were retrospectively evaluated. Diagnosis was confirmed by American Thoracic Society (ATS) guidelines and CT scans were reviewed in both lung and mediastinal windows. The average age of patients was 63 ± 14.54 years and 52.9% were male. The majority of patients had cough (91.2%) and sputum production (76.5%). Clinically, 41.2% of patients had previous history of TB (14/34), 38.2% had cardiac diseases (13/34), and 35.3% had diabetes mellitus (12/34). The most common CT findings in our study were nodular lesions (100%) and bronchiectasis (85.29%). Regarding the severity, grade I bronchiectasis was the most prevalent. Other prominent findings were tree-in-bud sign (88.2%), consolidation (52.94%), and lobar fibrosis and volume loss (67.6%). There was no significant zonal distribution of findings. In conclusion, nodular lesions and bronchiectasis are the most frequent features in CT scan of M. simiae pulmonary infection.

[Infections due to Mycobacterium simiae]

Mycobacterium simiae is a slow-growing photochromogenic environmental mycobacterium, first described in 1965. Rarely associated with human infections, possibly due to its limited pathogenicity, it mainly produces lung infection in immunocompetent elderly patients with underlying lung disease, and in disseminated infections in immunosuppressed young patients with AIDS. A microbiological culture is needed to confirm the clinical suspicion, and genetic sequencing techniques are essential to correctly identify the species. Treating M. simiae infections is complicated, owing to the multiple resistance to tuberculous drugs and the lack of correlation between in vitro susceptibility data and in vivo response. Proper treatment is yet to be defined, but must include clarithromycin combined with other antimicrobials such as moxifloxacin and cotrimoxazole. It is possible that M. simiae infections are undiagnosed.

Non-contiguous genome sequence of Mycobacterium simiae strain DSM 44165(T.)

Mycobacterium simiae is a non-tuberculosis mycobacterium causing pulmonary infections in both immunocompetent and imunocompromized patients. We announce the draft genome sequence of M. simiae DSM 44165^T. The 5,782,968-bp long genome with 65.15% GC content (one chromosome, no plasmid) contains 5,727 open reading frames (33% with unknown function and 11 ORFs sizing more than 5000 -bp), three rRNA operons, 52 tRNA, one 66-bp tmRNA matching with tmRNA tags from Mycobacterium avium, Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium microti, Mycobacterium marinum, and Mycobacterium africanum and 389 DNA repetitive sequences. Comparing ORFs and size distribution between M. simiae and five other Mycobacterium species M. simiae clustered with M. abscessus and M. smegmatis. A 40-kb prophage was predicted in addition to two prophage-like elements, 7-kb and 18-kb in size, but no mycobacteriophage was seen after the observation of 10⁶M. simiae cells. Fifteen putative CRISPRs were found. Three genes were predicted to encode resistance to aminoglycosides, betalactams and macrolide-lincosamide-streptogramin B. A total of 163 CAZYmes were annotated. M. simiae contains ESX-1 to ESX-5 genes encoding for a type-VII secretion system. Availability of the genome sequence may help depict the unique properties of this environmental, opportunistic pathogen.

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.

Necrotizing Cervical Lymphadenitis Caused by Mycobacterium simiae in an HIV-Positive Patient: Imaging with (18)F-FDG PET/CT

Mycobacterium simiae (M. simiae) is an opportunistic pathogen rarely associated with human disease, although in recent years M. simiae has been detected with increasing frequency in human immunodeficiency virus (HIV)-infected patients, usually causing disseminated infection with fever, diarrhea and weight loss. We report the case of an HIV-positive man, who was referred for an (18)F-FDG PET/CT to evaluate a solitary pulmonary nodule. The PET/CT showed incidental large necrotic cervical lymph nodes, compatible with necrotizing cervical lymphadenitis. Biopsy and culture of one of the affected lymph nodes were positive for M. simiae. We present the first report of (18)F-FDG PET/CT imaging of an infectious process caused by M. simiae in humans.

Mycobacterium simiae complex infection in an immunocompetent child

Nontuberculous mycobacteria are ubiquitous in the environment but rarely infect immunocompetent patients. We describe a pediatric case of Mycobacterium simiae complex lymphadenitis in an immunocompetent child and review the natural history, clinical manifestations, diagnosis, and current management of the disease.