SciCombinator

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Concept: Mycobacterium kansasii

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It has recently been shown that the anti-mycobacterial pro-drug thiacetazone (TAC) inhibits the conversion of double bonds of mycolic acid precursors into cyclopropyl rings in Mycobacterium bovis var BCG, M. marimum and M. chelonae by affecting the cyclopropyl mycolic acid synthases (CMASs) as judged by the build-up of unsaturated mycolate precursors. In our hands, TAC inhibits mycolic acid biosynthesis in Mycobacterium tuberculosis and M. kansasii with almost negligible accumulation of those precursors. Our observations that ‘de novo’ biosynthesis of all the mycolic acid families decreased upon TAC treatment prompted us to analyse the role of each one of the Type II Fatty Acid Synthase (FASII) enzymes. Overexpression of the hadABC operon, encoding the essential FASII dehydratase complex, but not of any of the remaining FASII genes acting on the elongation of fatty acyl chains leading to the synthesis of meromycolic acids, resulted in high level of resistance to TAC in M. tuberculosis. Spontaneous M. tuberculosis and M. kansasii TAC-resistant mutants isolated during this work revealed mutations in the hadABC genes strongly supporting our proposal that these enzymes are new players in the resistance to this anti-mycobacterial compound.

Concepts: Mycobacterium kansasii, Fatty acid, Fatty acid synthase, Mycobacterium tuberculosis, Acid fast bacilli, Tuberculosis, Corynebacterineae, Mycobacterium

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Mycobacterium kansasii is a pulmonary pathogen that has been grown readily from municipal water, but rarely isolated from natural waters. A definitive link between water exposure and disease has not been demonstrated and the environmental niche for this organism is poorly understood. Strain typing of clinical isolates has revealed seven subtypes with Type 1 being highly clonal and responsible for most infections worldwide. The prevalence of other subtypes varies geographically. In this study 49 water isolates are compared with 72 patient isolates from the same geographical area (Brisbane, Australia), using automated repetitive unit PCR (Diversilab) and ITS_RFLP. The clonality of the dominant clinical strain type is again demonstrated but with rep-PCR, strain variation within this group is evident comparable with other reported methods. There is significant heterogeneity of water isolates and very few are similar or related to the clinical isolates. This suggests that if water or aerosol transmission is the mode of infection, then point source contamination likely occurs from an alternative environmental source.

Concepts: Immune system, Infectious disease, Mycobacterium, Water, Water supply network, Disease, Mycobacterium kansasii, Drinking water

3

To meet the global needs of tuberculosis (TB) control, a nanoELIwell device was developed as a multifunctional assay for TB diagnosis and drug susceptibility testing. The device integrates on-chip culturing of mycobacteria, immunoassay, and high-resolution fluorescent imaging. Mycobacterium smegmatis and Mycobacterium kansasii were used as models of Mycobacterium tuberculosis to evaluate device integrity by using antigens, Ag85 and ESAT-6, as biomarkers. As a result, the nanoELIwell device detected antigens released from a single bacterium within 24-48-hour culture. Antimycobacterial drug-treated M. smegmatis showed significant decreased in Ag85 antigen production when treated with ethambutol and no change in antigen production when treated with rifampin, demonstrating drug susceptibility and resistance, respectively. The nanoELIwell assay also distinguished the ESAT-6-secreting M. kansasii from the non-ESAT-6-secreting M. simiae. The combination of microwell technology and ELISA assay holds potential to the development of a rapid, sensitive, and specific diagnostics and susceptibility testing of TB.

Concepts: Acid fast bacilli, ELISA, Antibody, Mycobacterium smegmatis, Mycobacterium kansasii, Corynebacterineae, Tuberculosis, Mycobacterium

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The evolution of tubercle bacilli parallels a route from environmental Mycobacterium kansasii, through intermediate “Mycobacterium canettii”, to the modern Mycobacterium tuberculosis complex. Cell envelope outer membrane lipids change systematically from hydrophilic lipooligosaccharides and phenolic glycolipids to hydrophobic phthiocerol dimycocerosates, di- and pentaacyl trehaloses and sulfoglycolipids. Such lipid changes point to a hydrophobic phenotype for M. tuberculosis sensu stricto. Using Congo Red staining and hexadecane-aqueous buffer partitioning, the hydrophobicity of rough morphology M. tuberculosis and Mycobacterium bovis strains was greater than smooth “M. canettii” and M. kansasii. Killed mycobacteria maintained differential hydrophobicity but defatted cells were similar, indicating that outer membrane lipids govern overall hydrophobicity. A rough M. tuberculosis H37Rv ΔpapA1 sulfoglycolipid-deficient mutant had significantly diminished Congo Red uptake though hexadecane-aqueous buffer partitioning was similar to H37Rv. An M. kansasii, ΔMKAN27435 partially lipooligosaccharide-deficient mutant absorbed marginally more Congo Red dye than the parent strain but was comparable in partition experiments. In evolving from ancestral mycobacteria, related to “M. canettii” and M. kansasii, modern M. tuberculosis probably became more hydrophobic by increasing the proportion of less polar lipids in the outer membrane. Importantly, such a change would enhance the capability for aerosol transmission, affecting virulence and pathogenicity.

Concepts: Nontuberculous mycobacteria, Mycobacterium bovis, Mycobacterium kansasii, Mycobacterium tuberculosis, Acid fast bacilli, Corynebacterineae, Tuberculosis, Mycobacterium

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Molecular epidemiological studies of Mycobacterium kansasii are hampered by the lack of highly-discriminatory genotyping modalities. The purpose of this study was to design a new, high-resolution fingerprinting method for M. kansasii. Complete genome sequence of the M. kansasii ATCC 12478 reference strain was searched for satellite-like repetitive DNA elements comprising tandem repeats. A total of 24 variable-number tandem repeat (VNTR) loci were identified with potential discriminatory capacity. Of these, 17 were used to study polymorphism among 67 M. kansasii strains representing six subtypes (I-VI). The results of VNTR typing were compared with those of pulsed-field gel electrophoresis (PFGE) with AsnI digestion. Six VNTRs i.e. (VNTR 1, 2, 8, 14, 20 and 23) allow to differentiate analyzed strains with the same discriminatory capacities as use of a 17-loci panel. VNTR typing and PFGE in conjunction revealed 45 distinct patterns, including 11 clusters with 33 isolates and 34 unique patterns. The Hunter-Gaston’s discriminatory index was 0.95 and 0.66 for PFGE and VNTR typing respectively, and 0.97 for the two methods combined. In conclusion, this study delivers a new typing scheme, based on VNTR polymorphism, and recommends it as a first-line test prior to PFGE analysis in a two-step typing strategy for M. kansasii.

Concepts: Gel electrophoresis, Molecular biology, Genetics, Mycobacterium kansasii, Variable number tandem repeat, Tandem repeat, Short tandem repeat, DNA

0

This study investigated the changes in the major etiologic organisms and clinical phenotypes of nontuberculous mycobacterial lung disease (NTM-LD) over a recent 15-year period in Korea. The increase of number of patients with NTM-LD was primarily due to an increase of Mycobacterium avium complex (MAC) lung disease (LD). Among MAC cases, the proportion of M. avium increased compared with M. intracellulare, whereas the incidence of M. abscessus complex and M. kansasii LD remained relatively stable. The proportion of cases of the nodular bronchiectatic form increased compared with the fibrocavitary form of NTM-LD.

Concepts: Mycobacterium kansasii, Medicine, Bacteria, Nontuberculous mycobacteria, Epidemiology, Tuberculosis, Mycobacterium, Mycobacterium avium complex

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We report two cases of pleurisy caused by non-tuberculous mycobacteria followed by pneumothorax. The onset of pleurisy was accompanied by acute fever. Cultured samples of the pleural effusions from the two patients, an 80-year-old man and an 87-year-old woman, were ultimately found to contain Mycobacterium intracellulare and Mycobacterium kansasii, respectively. Both patients were initially administered antibiotics, but their fevers persisted. Therefore, different combinations of antimycobacterial drugs were used, which reduced the fever in a few days. In these patients, pleurisy caused by non-tuberculous mycobacteria followed by pneumothorax was characterised by acute fever and improvement in the fever after administration of antimycobacterial drugs; however, the aetiology remains to be clarified.

Concepts: Mycobacterium avium complex, Nontuberculous mycobacteria, Acid fast bacilli, Mycobacterium intracellulare, Corynebacterineae, Mycobacterium kansasii, Tuberculosis, Mycobacterium

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Studies on drug susceptibility of Mycobacterium kansasii are very few and involve limited number of strains. The purpose of this study was to determine drug susceptibility profiles of M. kansasii isolates representing a spectrum of species genotypes (subtypes) with two different methodologies, i.e. broth microdilution and E-test assays. To confirm drug resistance, drug target genes were sequenced.A collection of 85 M. kansasii isolates, including representatives of eight different subtypes (I-VI, I/II, IIB) from eight countries was used. Drug susceptibility against 13 and 8 anti-mycobacterial agents was tested by using broth microdilution and E-test method, respectively. For drug-resistant or high-MIC isolates, eight structural genes (rrl, katG, inhA, embB, rrs, rpsL, gyrA, and gyrB) and one regulatory region (embCA) were PCR-amplified and sequenced in the search for resistance-associated mutations.All isolates tested were susceptible to rifampicin (RIF), amikacin (AMK), co-trimoxazole (SXT), rifabutin (RFB), moxifloxacin (MXF), and linezolid (LZD), when using microdilution method. Resistance to ethambutol (EMB), ciprofloxacin (CIP), and clarithromycin (CLR) was found in 83 (97.7%), 17 (20%), and 1 (1.2%) isolate, respectively. The calculated concordance between the E-test and dilution method was 22.6% for AMK, 4.8% for streptomycin (STR), 3.2% for CLR, and 1.6% for RIF. For EMB, INH, and SXT, not even a single MIC value determined by one method equaled that by the second method. The only mutations disclosed were A2266C transversion at rrl gene (CLR-resistant strain) and A128G transition at rpsL gene (strain with STR MIC >64 mg/L).In conclusion, eight drugs, including RIF, CLR, AMK, SXT, RFB, MXF, LZD, and ethionamide (ETO) showed high in vitro activity against M. kansasii isolates. Discrepancies of the results between the reference microdilution method and E-test precludes the use of the latter for drug susceptibility determination in M. kansasii Drug resistance in M. kansasii may have different genetic determinants than resistance to the same drugs in M. tuberculosis.

Concepts: Gene, DNA, Genetics, Tuberculosis treatment, Mycobacterium kansasii, Mycobacterium, Antibiotic resistance, Tuberculosis

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A 1-year-old, female domestic shorthair cat was presented with anorexia, depression and weight loss, accompanied by multifocal nodules affecting the face, pinnae and periarticular tissue. Routine medical treatments were ineffective. The animal’s physical condition continued to deteriorate and it finally died. Post-mortem examination revealed multifocal to coalescing firm nodules with occasional ulceration affecting the ears, peri-ocular areas, nasal planum, oral cavity and laryngopharyngeal region. Tan-coloured, firm, nodular lesions were also observed in the periarticular tissue, lungs and tracheobronchial and mediastinal lymph nodes. Impression smears of several of these lesions revealed a myriad of slender rod-shaped organisms, mainly in the cytoplasm of macrophages. Histopathological examination showed severe pyogranulomatous inflammation with or without necrosis in the nodules. Acid-fast staining revealed large numbers of acid-fast bacilli. Mycobacterium kansasii was detected in the tissues using multiplex polymerase chain reaction and DNA sequencing. No protozoal or fungal organisms were detected using special stains. On the basis of these results, the cat was diagnosed with systemic M. kansasii infection. To our knowledge, there have been few reports of M. kansasii infection, especially with systemic spread, in cats.

Concepts: Immune system, Mycobacterium, Polymerase chain reaction, Mycobacterium kansasii, Cat, Bacteria, Acid fast bacilli, DNA

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Typical cutaneous non-tuberculous mycobacteria (NTM) infections show a histopathology pattern of granulomas with admixed Langhans giant cells, and abscesses may be observed in acute lesions. Herein, we describe a patient carrying a high titer of autoantibodies to interferon (IFN)-γ with disseminated Mycobacterium kansasii infection presenting with emperipolesis and Rosai-Dorfman disease (RDD)-like histopathological features characterized by remarkable, large, pale-staining “RD cells”, which were CD68 and S100 positive and CD1a negative. The patient was misdiagnosed with RDD initially, but exhibited a poor response to all interventions. A re-biopsy revealed Langhans-type multinucleated giant cells; multiple definite acid-fast bacilli were also found. M. kansasii was isolated from cultured tissues. Anti-NTM treatment was initiated. After treatment, all lesions resolved almost completely within the following month. High-titer anti-IFN-γ autoantibodies were detected during follow up, leading to the diagnosis of adult-onset immunodeficiency syndrome. In conclusion, patients carrying high-titer autoantibodies to IFN-γ who also have a disseminated cutaneous M. kansasii infection may present with RDD-like histopathological features, which may be a pitfall in the diagnosis of disseminated cutaneous NTM infections.

Concepts: Tuberculosis, Nontuberculous mycobacteria, Mycobacterium, Anatomical pathology, Bacteria, Immune system, Mycobacterium kansasii, Acid fast bacilli