[Confirmation by molecular typing of cross-contamination in a mycobacteria laboratory]. / Confirmación mediante tipificación molecular de contaminaciones cruzadas en el laboratorio de micobacterias.

ABSTRACT

BACKGROUND: Detection of cross-contamination in the laboratory by restriction fragments length polymorphism (RFLP) analysis of Mycobacterium tuberculosis strains. MATERIAL AND METHODS: 224 strains isolated during a five years period were characterized by IS6110 fingerprinting performed (RFLP) by standardized protocols. RESULTS: Four groups of isolates with smear-negative specimens and low number of colony form its units were detected. They were processed in the same batch and day than other smear-positive specimens with identical RFLP patterns. Fifteen patients were involved and the review of four patients' charts showed that they did not have the typical manifestations of tuberculosis. CONCLUSIONS: When M. tuberculosis isolates were obtained from smear-negative specimens, the results of specimens processed in the same batch and the patients' charts should be reviewed. If with these data the possibility of cross-contamination is suspected, the isolates must be analyzed by molecular typing methods.