Automatized PCR evaluation ofMycobacterium tuberculosiscomplex in respiratory and nonrespiratory specimens

Abstract

In this study, Mycobacterium tuberculosis complex isolates recovered from respiratory and nonrespiratory specimens with culture were evaluated using an automatized PCR method. Specimens with suspected tuberculous disease were decontaminated and concentrated using the standard N-acetyl-L-cysteine NaOH method and were inoculated onto glycerol-supplemented Löwenstein-Jensen media and BACTEC B12 vials. Forty-one specimens with typical colonies on solid media and 127 specimens identified as M. tuberculosis complex in a BACTEC system were selected as the study group. As the control group, 46 specimens without growth on either culture media were selected. The PCR results were positive in 33 (80.5%) and 87 (68.5%) samples that were culture-positive on solid and liquid media, respectively. All (100%) culture-negative specimens within the control group were also negative in the COBAS AMPLICOR Mycobacterium tuberculosis (MTB) PCR method. In conclusion, although it is a fast method for identifying M. tuberculosis complex isolates from clinical specimens, the COBAS AMPLICOR MTB PCR method is found to be less sensitive than culture techniques, we propose therefore that it should only be used in combination with culture results in the clinical diagnosis of tuberculosis.

Diagnosis of tuberculous meningitis: clinical and laboratory parameters

“…Immunomagnetic enrichment of the CSF sample has led to improved sensitivity. 25 Commercially available nucleic acid amplification kits such as the Gen-Probe Amplified Direct test 26 and modification thereof, 27 and PCR kits such as the Cobas Amplicor, 28,29 have demonstrated sensitivities ranging from 60% to 83% and specificity of 100%.…”

Use of in-house PCR for identification of Mycobacterium tuberculosis in BACTEC broth cultures of respiratory specimens

“…To achieve better sensitivity than direct testing and better turnaround time than current culture and identification methods, mycobacteriology laboratories have been using commercially available nucleic acid amplification test kits to detect M. tuberculosis in BACTEC ® 12B medium cultures (Desmond & Loretz 2001). Despite considerable improvement of commercially available assays and their advantage in shortened turnaround times for diagnosis, these tests require a frequent supply of expensive commercial reagents or chips and are not expected to supplant culture for the definitive diagnosis of clinically significant mycobacterial infections (Bayram et al 2006).…”