Showing papers by "Abhay Chowdhary published in 2011"

Tuberculous brain abscesses: Case series and review of literature.

Abstract: Introduction: Tuberculous brain abscess (TBA) is a rare but serious condition. It resembles a pyogenic brain abscess clinically and radiologically and poses a problem in diagnosis and treatment. A final diagnosis is established by smear or culture demonstration of acid fast bacilli (AFB) within the abscess. Here, we report four such cases in our five-year study on brain abscesses, along with the different diagnostic modalities used. Materials and Methods: A total of 75 brain abscess pus specimens were collected during neurosurgery, either by burr hole or by craniotomy. These specimens were further subjected to Gram stain, Ziehl-Neelsen (ZN) stain, and conventional microbiological culture. Only those cases which showed presence of AFB on ZN stain along with the growth of Mycobacterium tuberculosis were considered as TBAs. Such TBA cases were further presented along with their In vitro Proton Magnetic Resonance (MR) Spectroscopic findings. Results: Of these four patients, three were males. Though this condition is more commonly seen in immunocompromised patients, three of the patients in this study were immunocompetent. All the four pus specimens showed presence of AFB in the ZN stain. Three of them grew M. tuberculosis as sole isolate. The fourth case was of concomitant tuberculous and pyogenic brain abscess. In vitro Proton MR spectroscopy of the pus specimens showed absence of multiple amino acids at 0.9 ppm, which was found to be hallmark of TBA. One patient died of four. Conclusions: TBA always poses a diagnostic dilemma. ZN stain and conventional microbiological culture for Mycobacteria always help to solve this dilemma. In vitro Proton MR Spectroscopy also seems to have the diagnostic utility.

Relationship between rpoB mutations and minimum inhibitory concentrations of rifampicin in multi drug resistant strains of mycobacterium tuberculosis

Abstract: Introduction: Rifampicin (RF) resistance serves as a surrogate marker for detection of multi drug resistant (MDR) strains of Mycobacterium tuberculosis (MTB). Among many mutations identified in rpoB gene, the target gene for detection of RF resistance, few were verified by molecular genetic methods. Aim: To detect and characterize mutations in rpoB region of MDR MTB strains by automated DNA sequencing. To study the relationship between in vitro Minimum Inhibitory Concentrations (MIC) for RF and rpoB mutations Methods: Absolute concentration method was used to determine MIC of RF for 20 MDR MTB strains. DNA sequencing was carried out in an ABI sequencer. Results: We could detect point mutations in the 81 bp section of a “hot spot” region of the rpoB gene of all the MDR strains. Mutations were detected in positions 516,526 and 531, with frequencies of 30%, 40%, and 55%, respectively. It was found that mutations in positions 526 and 531 conferred high-level resistance to RF (MIC9s ≥ 128μg/ml). Mutations in positions 516 relate to low-level resistance. (MIC9s ≤ 64μg/ml). Double point mutations in 2 isolates in positions 526 & 531 and 1 isolate in position 516 & 531 relate to high level resistance (MIC9s ≥ 128μg/ml), while 2 isolates in position 516 & 526 relate to low level resistance (MIC9s ≤ 64μg/ml). Conclusion: A relationship between susceptibility to RF and alterations in rpoB gene is observed. However, relationship between gene alteration and drug-resistant phenotype is still unclear, further analysis of the relationship between MICs and gene alteration is necessary.