Specimen contamination in mycobacteriology laboratory detected by pseudo-outbreak of multidrug-resistant tuberculosis: analysis by routine epidemiology and confirmation by molecular technique

A cluster of multidrug-resistant tuberculosis sputum isolates led to the detection of specimen contamination in a hospital mycobacteriology laboratory. Thirteen specimens were smear negative but culture positive from one specimen only; 12 appeared to be contaminated. Each of these specimens was processed in the same batch as one or more smear- and culture-positive isolates. Molecular analysis confirmed the traditional epidemiologic, laboratory, and clinical methods of evaluating presumed mycobacterial contamination.