Determination of polymerase chain reaction efficiency for diagnosis of tuberculous meningitis in Chelex-100 extracted DNA samples

SETTING

Polymerase chain reaction (PCR) offers great promise for the rapid, sensitive and specific diagnosis of tuberculous meningitis (TBM). However, the isolation of DNA of high quantity and quality from cerebrospinal fluid (CSF) samples is critical for successful PCR assays.

OBJECTIVE

To develop and use a single-tube method for the isolation of PCR-compatible DNA from Mycobacterium tuberculosis using Chelex-100 chelating resin, which does not require organic solvents or detergents.

DESIGN

The study focused on the standardisation of a suitable Chelex protocol and its evaluation in 32 CSF samples from TBM and non-TBM subjects. A simultaneous comparison was made with the conventional phenol/chloroform extraction method.

RESULT

PCR was found to be more sensitive, more rapid and less technically demanding with the Chelex protocol than the conventional phenol/chloroform extraction method (sensitivity 84.2% vs. 73.6%).

CONCLUSION

The single-tube method and the simplicity of the procedure permits early and reliable diagnosis of TBM and makes it an attractive method for routine laboratory assays.

Diagnostic value of early secreted antigenic target-6 for the diagnosis of tuberculous meningitis patients

BACKGROUND

The early diagnosis of tuberculous meningitis (TBM) is very crucial, since delayed diagnosis can lead to various neurological manifestations. We have previously developed an in-house indirect enzyme-linked immunosorbent assay (ELISA) for TBM diagnosis using the Antigen 85 (Ag 85) complex. It has been suggested that the Ag 85 complex might give false-positive reactions for individuals vaccinated with Bacillus Calmette-Guérin (BCG).

OBJECTIVES

In the present study, we describe a prospective evaluation demonstrating that early secreted antigenic target- 6 (ESAT-6), which is absent in Mycobacterium bovis BCG strains, is in the cerebrospinal fluid (CSF) of TBM patients.

METHODS

We used an indirect ELISA to detect ESAT-6 antigens in the CSF of TBM patients using polyclonal antibodies against ESAT-6.

RESULTS

Using the indirect ELISA method, we demonstrated a sensitivity and specificity of 80% and 94%, respectively, for the diagnosis of TBM.

CONCLUSION

The detection of ESAT-6 in the CSF of TBM patients by indirect ELISA is a promising method and can be used to develop an immunodiagnostic assay with increased sensitivity and specificity.

Serodiagnosis of tuberculosis based on the analysis of the 65 kD heat shock protein of Mycobacterium tuberculosis

OBJECTIVE

To evaluate the 65 kD heat shock protein (hsp) antigen in serum samples of tuberculosis (TB) patients by enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies (mAbs) specific to the 65 kD hsp antigen for the diagnosis of TB.

DESIGN

Serum samples were obtained from 188 different groups of patients (confirmed TB [n = 24], clinically suspected TB [n = 48], non-TB disease controls [n = 74] and healthy individuals [n = 42]) and analysed by ELISA using mAbs to the 65 kD hsp antigen. The Kruskal Wallis test (non-parametric analysis of variance) with the Dunnett post test was used for statistical analysis.

RESULTS

The method yielded 82% sensitivity and 89% specificity for the diagnosis of TB. The mean (+ or -SD) absorbance value of the 65 kD hsp antigen in TB patients (1.73 + or - 0.27) was significantly higher than in the non-TB disease control group (1.12 + or - 0.42, P < 0.001) and was also higher than among healthy individuals (1.06 + or - 0.42, P < 0.001).

CONCLUSION

The detection of the 65 kD hsp antigen in serum samples from confirmed and suspected TB patients by ELISA using mAb against purified 65 kD antigen gives a reliable diagnosis and could be considered as a diagnostic marker for TB. The absence of the 65 kD hsp antigen in healthy control BCG-vaccinated subjects indicates the diagnostic value of this assay in regions of endemicity.

Demonstration of IgG antibodies to 30 Kd protein antigen in CSF for diagnosis of tuberculous meningitis by antibody-capturing ELISA

OBJECTIVE

A simple and rapid immunological assay method has been developed to demonstrate the presence of IgG antibodies to 30Kd protein antigen (30Kdpa) and culture filtrate protein (CFP) in the CSF of patients with Tuberculous meningitis (TBM).

METHOD

Antibody capturing Enzyme Linked Immunosorbent Assay (ELISA) was standardized with CFP antigen of MTB. The IgG antibodies were assayed in CSF sample from TBM and non-TBM patients against 30 Kdpa.

RESULTS

The sensitivity and specificity of IgG antibodies for the diagnosis of suspected patients of TBM using 30 Kdpa was 80% and 91% respectively and the corresponding figures for CFP were 85% and 94% respectively. The sensitivity and specificity in two confirmed cases of TBM was 100%.

CONCLUSION

The presence of this 30Kdpa in the CSF of suspected cases of TBM consistently would indicate that the selected protein band carries the candidate protein marker antigen, which is specific to M. tuberculosis and could be considered as a diagnostic marker for TBM.

Serotyping and transferability of drug resistance in clinical isolates of E. coli

Forty nine multiple drug resistant strains of E. coli isolated from UTI were serotyped. The pattern was found to be 057 (eight strains); 0109 (four strains); 020, 038, 068, 0106, 0148. Rough (three each). 012, 054, 0101, 0160 (two each) and 02, 032, 046, 053, 060, 065, 090, 091, 0117, 0118, untypable (one each). The resistance pattern of all E. coli were identified and matted with recepient strain in penassay broth and in human urine. In a penassay broth transfer of resistance was demonstrated in 38 strains (77.5%) while in human urine transfer was demonstrated only in 14 strains (28.57%).