False-positive results from cultures of Mycobacterium tuberculosis due to laboratory cross-contamination confirmed by restriction fragment length polymorphism

Abstract

During 1994, a cross-contamination problem leading to false-positive cultures of Mycobacterium tuberculosis was revealed in a mycobacteriology laboratory processing 30,000 to 35,000 samples per year. Molecular strain typing based on restriction fragment length polymorphism confirmed the contaminations. Out of 1,439 positive cultures of Mycobacterium tuberculosis, 49 samples from 48 patients were suspected to be cross-contaminated. In 37 cases, growth was observed both in BACTEC vials and on solid media, indicating that the contamination took place during the processing of the samples. The majority of the contaminated samples had been handled by the same technician.

Molecular Fingerprinting of Mycobacterium tuberculosis and Risk Factors for Tuberculosis Transmission in Paris, France, and Surrounding Area

“…Confirmation of suspected cross contamination of specimens in mycobacteriology laboratories by molecular biology-based techniques has been reported previously (4,27,39). Our study reports that cultures for 24 (7.8%) patients were found to be falsely positive, and for 13 of these patients, the contamination was not suspected before strain fingerprinting.…”

Molecular epidemiology of tuberculosis and other mycobacterial infections: main methodologies and achievements

“…These errors can lead to unnecessary visits of falsely diagnosed patients to medical consultants and unnecessary long‐term antimicrobial treatment. Since the introduction of accurate strain typing methods, it has become clear that sampling and laboratory errors occur more frequently than previously assumed [240–245]. Small et al .…”

Results from 5 Years of Nationwide DNA Fingerprinting of Mycobacterium tuberculosis Complex Isolates in a Country with a Low Incidence of M. tuberculosis Infection

“…The stability and reproducibility of the technique as well as its usefulness in epidemiological studies has been convincingly demonstrated (8,16,17), and new insight into the nature of tuberculosis (TB) transmission has been obtained. Furthermore, RFLP has become an indispensable tool for quality assurance of the processing and culturing of patient samples, since it offers an opportunity to verify suspected cases of crosscontamination (2,13).…”