Mycobacterium diagnostics: from the primitive to the promising

Coinfection of disseminated Talaromyces marneffei and Mycobacteria kansasii in a patient with papillary thyroid cancer: A case report

RATIONALE

Recently, Talaromyces marneffei (T. marneffei) has been reported in human immunodeficiency virus (HIV)-negative patient with underlying diseases, such as oral cancer, colon cancer, haematological malignancies, connective tissue disease, diabetes mellitus, and corticosteroids or immunosuppressive agents. Similar to HIV-positive ones, such patients were observed with CD4 lymphocytopenia.

PATIENT CONCERNS

We reported a case of a 45-year-old woman who was diagnosed with disseminated T. marneffei and Mycobacteria kansasii (M. kansasii) with papillary thyroid cancer as the underlying disease. T-cell subsets counts, CD4 T-cell%, CD8 T-cell%, CD4/CD8 ratio, and NK cell% were all turned out to be normal.

DIAGNOSES

Based on bronchoalveolar lavage fluid and skin lesions secretion cultures, blood culture, the patient was diagnosed with disseminated T. marneffei and M. kansasii. Pathological examination reported papillary thyroid cancer with cervical lymph node metastasis.

INTERVENTIONS

The patient received the combined and longer antifungal therapy and drug regimens for M. kansasii. She had total thyroidectomy with radical neck dissection to treat the papillary thyroid cancer.

OUTCOMES

The patient had a favorable outcome for 19 months without recurrence.

LESSONS

T. marneffei could infect non-HIV individuals with underlying disease under the condition of normal T-cell counts. The symptoms were lack of specificity and were more likely to be misdiagnosed. Such patients with unidentified T-cell dysfunction or other unidentified primary immunodeficiency disorders may prone to coinfect with other opportunistic pathogens, such as M. kansasii. Compared with HIV-positive ones, they need combined and much longer antifungal therapy.

XtracTB Assay, a Mycobacterium tuberculosis molecular screening test with sensitivity approaching culture

Nucleic acid amplification tests are increasingly used to diagnose tuberculosis (TB) due to their speed and sensitivity compared to sputum smear microscopy. However, these tests fail to equal culture's sensitivity with sputum smear microscopy negative specimens and therefore cannot be used to rule out TB disease. For molecular tests to match culture's sensitivity, they must detect ≤10 genomic copies of Mycobacterium tuberculosis (MTB) DNA, the limit of detection of culture, process ≥1 ml of sputum ensuring sufficient number of MTB are in the reaction, and efficiently remove sputum associated inhibitors from this large sample. Here we report the preliminary characterization of XtracTB Assay, a MTB testing protocol designed for inclusion in either an integrated point-of-care platform or a high throughput automated central laboratory system. The test combines DNA sequence specific sample prep to reduce the co-extraction of qPCR inhibitors with the amplification of two MTB specific loci (IS6110 and senX3-regX3) to increase test sensitivity and minimize the likelihood of false negatives. The analytical sensitivity of the XtracTB Assay was 5 genomic copies/ml of sputum rivaling that of culture. Furthermore, 142 valid test results yield clinical sensitivity of 94.9% (95% CI: 90.1-99.9) and specificity of 100% (95% CI: 90.0-100.0).

The nematode Caenorhabditis elegans displays a chemotaxis behavior to tuberculosis-specific odorants

A simple, affordable diagnostic test for pulmonary tuberculosis (TB) is urgently needed to improve detection of active Mycobacterium tuberculosis. Recently, it has been suggested that animal behavior can be used as a biosensor to signal the presence of human disease. For example, the giant African pouched rats can detect tuberculosis by sniffing sputum specimens while trained honeybees respond to three of the volatile organic compounds (VOCs) detected in the breath of TB positive patients by proboscis extension. However, both rats and honeybees require animal housing facilities and professional trainers, which are outside the scope of most disease testing facilities. Here, we report that the innate olfactory behavioral response of the roundworm nematode Caenorhabditis elegans can be used to detect the TB-specific VOCs methyl p-anisate, methyl nicotinate, methyl phenylacetate and o-phenylanisole, in chemotaxis assays. Dauer larvae, a long-lived stress resistant alternative development state of C. elegans in which the animals can survive for extended periods of time in dry conditions with no food, were also demonstrated to detect the VOCs. We propose that exposing naive dauer larvae to TB-related VOCs and recording their response in this behavioral assay could lead to the development of a new method for TB diagnostics using breath as the sample type.

Temporal Expression of Peripheral Blood Leukocyte Biomarkers in a Macaca fascicularis Infection Model of Tuberculosis; Comparison with Human Datasets and Analysis with Parametric/Non-parametric Tools for Improved Diagnostic Biomarker Identification

A temporal study of gene expression in peripheral blood leukocytes (PBLs) from a Mycobacterium tuberculosis primary, pulmonary challenge model Macaca fascicularis has been conducted. PBL samples were taken prior to challenge and at one, two, four and six weeks post-challenge and labelled, purified RNAs hybridised to Operon Human Genome AROS V4.0 slides. Data analyses revealed a large number of differentially regulated gene entities, which exhibited temporal profiles of expression across the time course study. Further data refinements identified groups of key markers showing group-specific expression patterns, with a substantial reprogramming event evident at the four to six week interval. Selected statistically-significant gene entities from this study and other immune and apoptotic markers were validated using qPCR, which confirmed many of the results obtained using microarray hybridisation. These showed evidence of a step-change in gene expression from an ‘early’ FOS-associated response, to a ‘late’ predominantly type I interferon-driven response, with coincident reduction of expression of other markers. Loss of T-cell-associate marker expression was observed in responsive animals, with concordant elevation of markers which may be associated with a myeloid suppressor cell phenotype e.g. CD163. The animals in the study were of different lineages and these Chinese and Mauritian cynomolgous macaque lines showed clear evidence of differing susceptibilities to Tuberculosis challenge. We determined a number of key differences in response profiles between the groups, particularly in expression of T-cell and apoptotic makers, amongst others. These have provided interesting insights into innate susceptibility related to different host `phenotypes. Using a combination of parametric and non-parametric artificial neural network analyses we have identified key genes and regulatory pathways which may be important in early and adaptive responses to TB. Using comparisons between data outputs of each analytical pipeline and comparisons with previously published Human TB datasets, we have delineated a subset of gene entities which may be of use for biomarker diagnostic test development.