title: Infrequent MODS TB culture cross-contamination in a high-burden resource-poor setting.
abstract: 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% (17/10248) 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.
authors: Department of Infectious Diseases and Immunity, Imperial College London Wellcome Centre for Clinical Tropical Medicine, W12 0NN London, UK. davidajmoore@msn.com
authors: David A J
authors: DA
authors: Moore
authors: Luz
authors: L
authors: Caviedes
authors: Robert H
authors: RH
authors: Gilman
authors: Jorge
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authors: Coronel
authors: Fanny
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authors: Arenas
authors: Doris
authors: D
authors: LaChira
authors: Cayo
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authors: Salazar
authors: Juan
authors: J
authors: Carlos Saravia
authors: Richard A
authors: RA
authors: Oberhelman
authors: Maria-Graciela
authors: MG
authors: Hollm-Delgado
authors: A Roderick
authors: AR
authors: Escombe
authors: Carlton A W
authors: CA
authors: Evans
authors: Jon S
authors: JS
authors: Friedland