Liquid Culture Technology Provides Faster Results for TB Identification

A liquid culture system is now available in which mycobacteria will grow faster. The system is more accurate than conventional methods.

Liquid culture systems reduce the delays in obtaining results by one to two weeks over solid media. The new apparatus uses advanced fluorometric technology, which permits highly accurate detection of oxygen consumption by the bacteria in the special organism specific media.

The BD BACTEC MGIT 320 System (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) uses Mycobacteria Growth Indicator Tube (MGIT) media with easy access to the medium and a simple, four-step instrument workflow. The system is designed for laboratories with small work volumes and is fully automated. It holds 320 tubes, with a capacity of approximately 2,700 specimens per year. It makes optimal use of valuable laboratory space and offers a flexible configuration as either a bench-top or a stand-mounted instrument.

The media comes in plastic screw-cap tubes and does not require needles to inoculate or subculture the test tubes, eliminating the risk of needlestick injuries while inoculating tubes or working up positive cultures. Mycobacterial culture is more sensitive than microscopy, but growth of tubercle bacilli (TB) on traditional solid media typically requires two to four weeks and as many as eight weeks, of incubation. This consequently delays appropriate treatment in the absence of a confirmed diagnosis. Liquid culture systems reduce the delays in obtaining results by one to two weeks over solid media. For drug susceptibility testing (DST), the interval may be reduced to as little as ten days, compared with 28 to 42 days with conventional solid media. Liquid systems are more sensitive for detection of mycobacteria and may increase the case yield by 10% over solid media. With increased sensitivity and reduced delays, liquid systems will contribute significantly to improved patient management.

Philippe Jacon, president of BD Diagnostics - Diagnostic Systems said "Quick, safe, efficient testing is critical in the diagnosis of TB.” The rapid and accurate diagnosis of symptomatic patients is the cornerstone of global strategies for TB control.

It is estimated that the largest number of new TB cases in 2008 occurred in the South-East Asia region, which accounted for 34% of incident cases globally. However, the estimated incidence rate in sub-Saharan Africa is nearly twice that of the South-East Asia region with over 350 cases per 100,000 population.

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