A strip-based assay for detection of CrfA enzyme activity to differentiate Mycobacterium tuberculosis and non-tuberculous mycobacteria.

There is an unmet need for tools that permit diagnosis of Tuberculosis (TB) that are affordable, low-tech, and can differentiate Mycobacterium tuberculosis (M.tb) from non-tuberculous mycobacteria (NTM). In this study, we have developed a strip-based assay to detect the activity of a unique Carbapenem Resistance Factor A (CrfA) enzyme present only in M.tb. The strip comprises of PVDF (Polyvinylidene fluoride) membrane that has an immobilized anti-CrfA antibody to capture the CrfA enzyme from M.tb lysate. Lysate of mycobacteria is applied to the strip, washed, and incubated in the presence of chromogenic reporter dye which is a substrate for CrfA. A change in the color of the dye that is readily visible to the naked eye is the readout. We evaluated lysates from M.tb and various NTMs namely, M. abscessus, M. chelonae, M. avium, M. obuense, M. paraintracellulare, M. kansasi, including the patient-derived sputum samples. The strip assay selectively identified only those samples containing M.tb. Based on this evidence, this new assay enables the identification and differentiation of M.tb from NTMs in patient sputum samples. As this tool can be simple to use, therefore has the potential to serve the unmet need for diagnosis of TB and NTM infections in resource-limited settings.

Initial experiences with a new MRI scoring system for differentiating advanced femoral osteonecrosis from tubercular arthritis.

The purpose of this study was to formulate a magnetic resonance imaging-based scoring system for differentiating tuberculous arthritis from advanced osteonecrosis of the femoral head. Magnetic resonance imaging findings in 18 hips with tuberculous arthritis and 36 hips with advanced osteonecrosis of the femoral head were reviewed retrospectively. Confirmation of tuberculous arthritis was based on enzyme-linked immunosorbent assay and/or synovial biopsy. Osteonecrosis was confirmed either by histopathology or eventual radiographic evidence on follow-up. The findings were analyzed with an emphasis on the changes in femoral head marrow, joint cavity, synovium, acetabulum, and contrast enhancement patterns. A score of 2 was assigned for the presence of each of the following: T2 hyperintensity of the femoral head, synovial hypertrophy, articular cartilage erosion, unilateral involvement of the femoral head, acetabular edema/sclerosis, and enhancement of the involved head. A score of 1 was assigned for each of the following: joint effusion, edema of adjacent marrow, and enhancement of adjacent soft tissue. A cutoff value of 10 of 15 points was considered to be positive for tuberculous arthritis. Sixteen of 18 cases of tuberculous arthritis were correctly identifiable on the basis of this scoring system. The 2 remaining cases had a score of 9. No case of osteonecrosis of the femoral head scored more than 9. A score of 10 for a positive diagnosis of tuberculous arthritis had a sensitivity of 88.89% and specificity of 100%. Positive and negative predictive values were 1 and 0.94, respectively. Statistical significance for each of the parameters and the entire model was established with logistic regression analysis. This new scoring system is effective in solving the imaging dilemma pertinent to endemic regions.

Post-operative sinus formation due to Mycobacterium abscessus: a case report.

SUMMARY: Mycobacterium abscessus is ubiquitously found rapidly growing mycobacteria. Although it is an uncommon pathogen, it has been known to cause cutaneous infection following inoculation, minor trauma or surgery. This communication reports an immuno-competent patient developing multiple sinuses due to Mycobacterium abscessus in the post- operative period.

Acute and chronic Chlamydia pneumoniae infection and inflammatory markers in coronary artery disease patients.

INTRODUCTION: We evaluated the role of inflammation and acute or persistent Chlamydia pneumoniae infection in coronary artery disease (CAD).      METHODOLOGY: The study involved 63 cardiovascular disease patients diagnosed with angina and myocardial infarction (MI) and 40 healthy controls. ELISA was performed for detection of C. pneumoniae IgA antibodies and for quantitative analysis of IFN-γ. PCR was performed for detection of the C. pneumoniae 16 SrRNA gene in blood. RESULTS: C. pneumoniae IgA antibodies were detected in 66.66% cases and 41.37% controls. Of IgA seropositive cases 71.43% were MI patients, 61.90% were stable angina patients, and 64.29% unstable angina patients. Of 40 patients whose PCR was done 32.5% were positive of which 76.92% were IgA seropositive. Traditional risk factors were not significantly associated with CAD. The mean value of IFN-γ in cases was 32.12pg/ml and 11.32pg/ml in controls. Elevated IFN-γ was observed in 76.92% of C. pneumoniae IgA seropositives with a mean value of IFN-γ in angina patients of 3.39pg/ml, in unstable angina of 12.91 pg/ml and in MI patients of 23.89 pg/ml. IFN-γ levels in cases who were positive for C. pneumoniae infection by serology and PCR was 55.21 pg/ml. CONCLUSION: C. pneumoniae infection was significantly associated with CAD risk. The role of acute or persistent infection in progression of CAD to adverse clinical outcome was evident by a high percentage of seropositives among PCR positives. Although IFN-γ alone had a role to play in development of CAD, its values were further enhanced due to recurrent C. pneumoniae infection.