Rapid Detection of Mycobacterium tuberculosis and Rifampin Resistance by Use of On-Demand, Near-Patient Technology

Abstract

Current nucleic acid amplification methods to detect

Laboratory evaluation of a specimen transport medium for downstream molecular processing of sputum samples to detect Mycobacterium tuberculosis

“…The rapid inactivation is in line with findings from Daum et al (2014), which showed that PS-MTM is an effective medium to inactivate a pure culture of M. tuberculosis at ~10 6 CFU/ml at an exposure time of 30 minutes. This is a similar effect as achieved by the Xpert SR buffer where an 8 and 9 log reduction was demonstrated at 15 minutes and 2 hours respectively (Helb, et al, 2010). A minimum time of 60 minutes from collection to specimen processing is likely to be routine and will provide a safe specimen for downstream testing, particularly in resource-constrained settings.…”

“…However, the only relevant published data on the effect of reagents added directly to sputum on the viability of TB bacilli is the sample reagent buffer (SR) of the Xpert assay. The SR has demonstrated capability of producing an 8 log reduction, within 15 minutes, in M. tuberculosis viability in sputum spiked with this organism (Helb et al, 2010). In M. tuberculosis-positive sputum specimens, with bacillary loads of less than 10 7 colony forming units/milliliter (CFU/ml), total inactivation was achieved within 15 minutes (Banada et al, 2010).…”

“…The SR has demonstrated capability of producing an 8 log reduction, within 15 minutes, in M. tuberculosis viability in sputum spiked with this organism (Helb et al, 2010). In M. tuberculosis-positive sputum specimens, with bacillary loads of less than 10 7 colony forming units/milliliter (CFU/ml), total inactivation was achieved within 15 minutes (Banada et al, 2010). In practice, the SR buffer is only added to the sample when processed at the laboratory and not intended for specimen transport.…”

“…However, studies on other pathogens in different clinical specimens have shown a negative effect on molecular testing when kept at ambient temperature for extended periods of time (Hasan et al, 2012, Ingersoll et al, 2008. In that context, the manufacturer of the Xpert assay recommends that sputum samples be kept for no longer than 3 days at ambient temperatures up to 35° C until processing (Banada, et al, 2010). Delays in transport and testing could negatively affect the diagnostic yield when using sputum specimens.…”

Diagnosis of Mycobacterium tuberculosis using molecular biology technology

“…Although sputum smear test is quicker and produces results in about 30 min, it can only detect 10% to 75% of TB cases and requires trained microscopists. In developing countries, the technical expertise and tools needed to perform these tests are limited, and TB is often not diagnosed or treated early, which allows the disease to spread quickly in crowded living quarters and to build resistance to the drugs used in the treatment of the infection [17,18] .…”