Use of bactec 460 TB system in the diagnosis of tuberculosis.

PURPOSE: To evaluate, the efficacy of BACTEC 460 TB system for the diagnosis of tuberculosis in a tertiary care hospital in Mumbai, India. METHODS: We compared 12,726 clinical specimens using BACTEC 460 TB system and conventional method for detection of Mycobacterium tuberculosis over a period of six years. Result: The overall recovery rate was 39% by BACTEC technique and 29% using Lowenstein-Jensen (LJ) medium. An average detection time for B actec0 460 TB system was found to be 13.3 days and 15.3 days as against 31.2 days and 35.3 days by LJ method for respiratory and nonrespiratory specimens respectively. The average reporting time for drug susceptibility results ranged from 6-10 days for the BACTEC 460 TB system. CONCLUSIONS: The BACTEC system is a good system for level II laboratories, especially in the diagnosis of extrapulmonary and smear negative tuberculosis.

Newer rapid diagnostic methods for tuberculosis: A preliminary experience.

Background:Present scenario of tuberculosis (TB) demands a reliable method for rapid diagnosis of TB. Several newer methodologies have been introduced over last 2 decades. However, clinical evaluation of all these methods is essential before bringing them into routine diagnostic practice. Aim: In the present study, we have evaluated 3 most promising methodologies viz. BACTEC 460 TB system (TB BACTEC), Transcription Mediated Amplification (TMA) and Phage assay for rapid detection of M. tuberculosis complex directly from respiratory and non-respiratory specimens. Material and Methods: Total 139 AFB smear positive and 41 AFB smear negative respiratory and non-respiratory specimens were tested by these methods and results were compared with conventional LJ method. Results and Conclusions: TMA is found to be most rapid and reliable method for detection of M. Tuberculosis complex from respiratory specimens with 93.8% sensitivity. However, for non-respiratory samples, TB BACTEC can be the method of choice. An average detection time for TB BACTEC is found to be 13 days and 15 days, compared to 31 days 35 days by LJ method in cases of smear positive respiratory and non-respiratory specimens respectively. Phage assay is highly specific for detecting M. tuberculosis complex and can be used as a rapid screening method for TB in cases of respiratory specimens collected from patients not receiving anti-TB therapy. As only viable TB bacilli are detected by phage assay, it can be used as a sensitive tool to monitor treatment success.

Rapid detection of rifampicin resistance in m.tuberculosis by phage assay.

Increase in multidrug-resistant M.tuberculosis (MDR-TB) has become a great cause of concern and rifampicin resistance is considered to be a good predictor of MDR-TB in many parts of the world. Its rapid detection will allow alteration in treatment regimens in time to reduce the spread of the disease. Detection of rifampicin resistance by phage assay is a useful tool as mycobacteriophages are specific for M.tuberculosis complex and detect viable cells only. In our study, we analyzed 85 samples for rifampicin resistance using a novel mycobacteriophage based test (Phage assay) and radiometric BACTEC 460 TB. Of the 85 samples, 70 (82.35%) were resistant and 12 (14.10%) were sensitive by both methods. Our study yielded a sensitivity and specificity of 100% and 80% respectively. A good correlation was observed with conventional LJ proportion method. We conclude that phage assay allows determination of rifampicin resistance within 48 hours from culture, reducing the time taken to define susceptibility results by BACTEC 460 TB and LJ proportion method (5-7 days and 6-8 weeks respectively).

Evaluation of a new phage amplification technology for rapid diagnosis of tuberculosis.

PURPOSE: Rapid diagnosis of tuberculosis is essential to initiate timely and appropriate treatment to curb the spread of this potentially life threatening disease. The purpose of this study was to evaluate a phage amplification technology viz., FASTPlaque TB,TM for the diagnosis of tuberculosis. METHODS: We evaluated the clinical utility of this new assay by analyzing 50 respiratory and 40 non-respiratory specimens, using FASTPlaque TB TM kit (Biotec Laboratories, UK) and the performance was compared with TB Bactec 460 semi-automated liquid culture system and conventional LJ culture method. RESULTS: In case of respiratory specimens phage assay gave good specificity (100%) compared with TB Bactec whereas with respect to LJ method the sensitivity and specificity were 93.1% and 88.2% respectively. In case of non-respiratory specimens comparison of results obtained by phage assay showed sensitivity of 90.9% and specificity of 88.8% with respect to TB Bactec and 87.5% and 93.8% with respect to LJ method. CONCLUSIONS: We believe that this new low cost assay may have widespread applicability, especially in developing countries, due to its manual format and rapid reporting of results.

Comparative study of amoxycillin and amoxycillin/clavulanic acid in lower respiratory infections.

A comparison of oral amoxycillin (500 mg tds) with amoxycillin/clavulanic acid (Augmentin; 750 mg tds) for 7 to 10 days was completed in 76 patients with lower respiratory infection. In another 9 patients, intravenous Augmentin alone was administered (1.2 g 8 hourly) for 3 days followed by oral doses as above for 7 days. In 50 (59%) patients the underlying chronic lung disease was bronchiectasis. Clinical improvement (1 + or more) was seen in 66% with amoxycillin, 60% with oral Augmentin and 56% with IV Augmentin. For radiographic improvement the respective figures were 47, 53 and 44 per cent. Bacteriologically, elimination was seen in 8% with amoxycillin and 45% with Augmentin (P less than 0.01), while partial success was seen in 16 and 24 per cent respectively. While for gram positive organisms, both drugs were similar in efficacy, for gram negative strains the overall success was 27% with amoxycillin and 67% with Augmentin. The main organisms isolated were Str pneumoniae (12), Klebsiella (41), Pseudomonas (21), E coli (9), Haemophilus (7) and Staph aureus (6). For bacteriologic sensitivity and consequent success, Augmentin may be superior in respiratory infections.