Rapid culture diagnosis of tuberculous lymphadenitis from a tertiary care centre in an endemic nation: Potential and pitfalls.

In spite of low sensitivity and specificity, standard diagnostic algorithm recommends fine needle aspiration cytology (FNAC) and direct microscopic screening for acid-fast bacilli (AFB) for the routine diagnosis of tuberculous lymphadenopathy (LNTB). In this study, the diagnostic utility of liquid broth based automated culture (BacT/ALERT 3D) technique was assessed in comparison with conventional techniques in 89 clinically suspected tubercular lymphadenitis patients. 60% (n = 53) were positive by FNAC and 38.4% (n = 34) demonstrated AFB in smear examination. BacT/ALERT yielded isolation in 43.1% (n = 38) aspirates, confirming tubercular aetiology. We also found six paediatric culture-positive cases which showed negative outcome by both FNAC and smear. Thus, we conclude that culture by BacT/ALERT, may be used for faster yield of Mycobacteria in LNTB, especially in children. Additionally, this could also be used as a platform for further differentiation of Mycobacterium tuberculosis from non-tuberculous mycobacteria (NTM) infection and for testing of anti-tubercular chemotherapeutic agents whenever drug resistance is suspected.

Assessment of trends of ofloxacin resistance in Mycobacterium tuberculosis.

Purpose: Ofloxacin (OFX) is one of the potent fluoroquinolone (FQ) recommended to treat MDR-TB. Over a decade, the preexposure of this drug for the treatment of other bacterial infections has resulted in acquisition of FQ resistance among Mycobacterium tuberculosis strains. Considering this possibility, a study was undertaken in a tertiary care center in the capital city (India) to assess the drug resistance trends of OFX among susceptible and multidrug resistant (MDR) strains of M. tuberculosis. Materials and Methods: A total of 102 M. tuberculosis isolates (47 susceptible to first-line drugs and 55 MDR isolates) were screened for susceptibility testing of OFX with a critical concentration of 2 μg/ml by Lowenstein Jensen (LJ) proportion method. Results: The results showed 40 (85.1%) isolates among 47 susceptible isolates and 34 (61.8%) isolates among 55 MDR isolates, were found to be susceptible to OFX. Fisher's exact test showed significant P-value (0.0136) demonstrating 1.377 fold (95% confidence interval) increased risk to become resistant to OFX than susceptible isolates. These finding shows decreased OFX susceptibility is not only limited to MDR isolates but also increasingly seen in susceptible strains as a result of drug abuse. Conclusions: Our finding were not alarming, but highlights the general risk of acquiring resistance to OFX, jeopardizing the potential for these drugs to be used as second-line anti-TB agents in the management of drug-resistant TB and creating incurable TB strains.

Evaluation of Nucleic Acid Probe for Rapid Identification of Mycobacterium tuberculosis Complex in Extra-Pulmonary Culture Isolates.

Patients infected with Non-tuberculous mycobacteria (NTM) usually do not respond to conventional anti-tubercular treatment and are misdiagnosed as infection with multi-drug resistant strains of mycobacterium tuberculosis (M.tb) due to lack of correct species identification, particularly in the developing countries like India. One of the challenges faced by clinicians in the treatment of tuberculosis is the absence of an easy, reliable and rapid identification tool that can accurately differentiate disease caused by M.tb complex from NTM. Keeping this in consideration, the performance of species specific nucleic acid probe i.e. Accuprobe was assessed and compared with conventional niacin production, nitrate reductase assay techniques for identification of M.tb complex in 80 mycobacterial isolates obtained from different extra - pulmonary sites. Accuprobe identified 62 isolates (77.5%) as M. tuberculosis complex and remaining 18 isolates (22.5%) as NTM whereas 64 isolates (80%) were identified as M.tb and rest 16 (20%) were interpreted as NTM by conventional biochemical techniques. The overall agreement between both techniques was 96.9% The sensitivity, specificity, positive predictive value(PPV) and negative predictive value (NPV) shown by accuprobe were 96.9%, 100%, 96.9%, and 88.9% respectively. Thus, accuprobe has showed impressive sensitivity and specificity giving results in <3 hrs from culture-positive isolates and have sure edge over conventional biochemical methods which are, nonetheless, labour intensive and cumbersome to perform thus delaying prompt mycobacterial identification.