title: Xpert(®) MTB/RIF detection of Mycobacterium tuberculosis from sputum collected in molecular transport medium.
abstract: The Xpert(®) MTB/RIF assay is widely used for Mycobacterium tuberculosis detection. However, specimen transport remains a challenge. PrimeStore Molecular Transport Medium(®) (PS-MTM) inactivates specimens and stabilizes DNA/RNA at ambient temperature for subsequent molecular detection.
  
  
  
  To compare the detection of M. tuberculosis concentrations in PS-MTM using Xpert and real-time polymerase chain reaction (RT-PCR), and smear-positive sputum specimens collected using a flocked swab.
  
  
  
  Dilutions of M. tuberculosis in PS-MTM and phosphate buffered saline (PBS) were analyzed using the Xpert assay and commercial RT-PCR. Smear-positive (1+ to 3+) sputum specimens (n = 17) were transferred by flocked swab into PS-MTM and PBS, and were compared to standard 1.0 ml sputum Xpert analysis.
  
  
  
  Using the Xpert assay, cycle threshold values from high M. tuberculosis concentrations in PS-MTM (>10(3) colony forming units [cfu]/ml) were increased compared to control. In contrast, M. tuberculosis samples containing <10(3) cfu/ml, i.e., low concentrations, suspended in PS-MTM resulted in detection down to 10 cfu/ml. Xpert detection efficiency in PS-MTM treated samples (63.2%) was improved compared to PBS controls (34.9%). Xpert detected M. tuberculosis in all sputum specimens collected by flocked swabs in PS-MTM, and correlated with routine Xpert detection.
  
  
  
  PS-MTM enhances M. tuberculosis detection at low concentrations of M. tuberculosis, and provides a simplified and efficient collection method for Xpert detection.
authors.affiliation: Longhorn Vaccines and Diagnostics, San Antonio, Texas, USA.
authors.forename: L T
authors.initials: LT
authors.lastname: Daum
authors.affiliation: University of Pretoria, Pretoria, South Africa.
authors.forename: P B
authors.initials: PB
authors.lastname: Fourie
authors.affiliation: University of Pretoria, Pretoria, Anova Health Institute, Johannesburg, South Africa.
authors.forename: R P H
authors.initials: RP
authors.lastname: Peters
authors.affiliation: Longhorn Vaccines and Diagnostics, San Antonio, Texas, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Rodriguez
authors.affiliation: Longhorn Vaccines and Diagnostics, San Antonio, Texas, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Worthy
authors.affiliation: City of Milwaukee Health Department Laboratory, Milwaukee, Wisconsin, USA.
authors.forename: M
authors.initials: M
authors.lastname: Khubbar
authors.affiliation: City of Milwaukee Health Department Laboratory, Milwaukee, Wisconsin, USA.
authors.forename: S
authors.initials: S
authors.lastname: Bhattacharyya
authors.affiliation: City of Milwaukee Health Department Laboratory, Milwaukee, Wisconsin, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Gradus
authors.affiliation: University of Pretoria, Pretoria, South Africa.
authors.forename: T
authors.initials: T
authors.lastname: Mboneni
authors.affiliation: University of Pretoria, Pretoria, South Africa.
authors.forename: E E
authors.initials: EE
authors.lastname: Marubini
authors.affiliation: Longhorn Vaccines and Diagnostics, San Antonio, Texas, USA.
authors.forename: C
authors.initials: C
authors.lastname: Helm
authors.affiliation: University of Texas at San Antonio, San Antonio, Texas, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Chambers
authors.affiliation: Longhorn Vaccines and Diagnostics, San Antonio, Texas, USA.
authors.forename: G W
authors.initials: GW
authors.lastname: Fischer
mesh_terms: D006801:Humans; D025202:Molecular Diagnostic Techniques; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000254:growth & development; D011237:Predictive Value of Tests; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013048:Specimen Handling / Q000379:methods*; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology