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

• DOI: 10.1016/j.diagmicrobio.2006.03.009
• Publication Date: 2006-05-07T11:12:53Z
• Authors: David A.J. Moore; Luz Caviedes; Robert H. Gilman; Jorge Coronel; Fanny Arenas; Doris LaChira; Cayo Salazar; Juan Carlos Saravia; Richard A. Oberhe...; Maria-Graciela Ho...; A. Roderick Escombe; Carlton A.W. Evans; Jon S. Friedland
• Keywords: Microbiological Techniques; 0301 basic medicine; 0303 health sciences; Sputum; Microbial Sensitivity Tests; Mycobacterium tuberculosis; DNA Fingerprinting; Specimen Handling; 3. Good health; 03 medical and health sciences; Cost of Illness; Tuberculosis, Multidrug-Resistant; Equipment Contamination; Health Resources; Humans; Tuberculosis

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.