Enzyme Discovered May Lead to Better TB Test

An enzyme has been identified that will trigger the rapid breakdown of several Mycobacteria, which could lead to better tests for the deadly tuberculosis infection.

The current bacterial culture test for tuberculosis infections is highly accurate but time-consuming, taking up to several weeks, while the diagnostic process called nucleic acid-based amplification (NAA) faces difficulty in breaking open, or lysing bacteria.

Scientists at University of Pittsburgh Graduate School of Public Health (PA, USA) show that exposure to an enzyme called esterase from Mycobacterium smegmatis hydrolyzes the ester linkage of trehalose dimycolate in vitro, which triggers the rapid and efficient lysis of Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium marinum.

A rapid and efficient lysis of trehalose dimycolate hydrolase (TDMH) exposed M. tuberculosis, and a subsequent release of nucleic acids (NA) offered a unique opportunity to use this enzyme for achieving more sensitive detection in a nucleic acid amplification assay for the diagnosis of tuberculosis (TB). The nucleic content in the supernatant of TDMH-exposed bacilli started to increase within 30 minutes of exposure, and it peaked at around 60 minutes.

Treatment of samples with TDMH prior to the amplification reaction facilitated the NA detection in 37 samples, a highly significant improvement in the numbers of positive detection. The investigators also demonstrated that this quick lysis of M. tuberculosis improved its detection at lower density.

Anil Ojha, PhD, an assistant professor and senior author of the study said, "Tuberculosis is a huge public health burden. Clearly, controlling the infection is heavily dependent upon an effective diagnosis. Discovery of enzyme-based mycobacteria lysis has the potential to increase the sensitivity of NAA." The study was published on January 4, 2013, in the Journal of Biological Chemistry.

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