Infrequent MODS TB culture cross-contamination in a high-burden resource-poor setting

David A.J. Moore, Luz Caviedes, Robert H. Gilman, Jorge Coronel, Fanny Arenas, Doris LaChira, Cayo Salazar, Juan Carlos Saravia, Richard A. Oberhelman, Maria Graciela Hollm-Delgado, A. Roderick Escombe, Carlton A.W. Evans, Jon S. Friedland

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


One obstacle to wider use of rapid liquid culture-based tuberculosis diagnostics such as the microscopic observation drug susceptibility (MODS) assay is concern about cross-contamination. We investigated the rate of laboratory cross-contamination in MODS, automated MBBacT, and Lowenstein-Jensen (LJ) cultures performed in parallel, through triangulation of microbiologic (reculturing stored samples), molecular (spoligotype/RFLP), and clinical epidemiologic data. At least 1 culture was positive for Mycobacterium tuberculosis for 362 (11%) of 3416 samples; 53 were regarded as potential cross-contamination suspects. Cross-contamination accounted for 17 false-positive cultures from 14 samples representing 0.41% (14/3416) and 0.17% (17/10 248) of samples and cultures, respectively. Positive predictive values for MODS, MBBacT (bioMérieux, Durham, NC), and LJ were 99.1%, 98.7%, and 99.7%, and specificity was 99.9% for all 3. Low rates of cross-contamination are achievable in mycobacterial laboratories in resource-poor settings even when a large proportion of samples are infectious and highly sensitive liquid culture-based diagnostics such as MODS are used.

Original languageEnglish (US)
Pages (from-to)35-43
Number of pages9
JournalDiagnostic Microbiology and Infectious Disease
Issue number1
StatePublished - Sep 2006


  • Cross-contamination
  • MODS
  • Microbacterial culture
  • Microscopic observation drug susceptability assay
  • Multidrug resistance
  • Tubercolosis

ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases


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