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Rapid detection of laboratory cross-contamination with Mycobacterium tuberculosis using multispacer sequence typing

DOI: 10.1186/1471-2180-9-47

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Abstract:

MST analysis indicated a unique and common sequence profile between a strain isolated from a patient with proven pulmonary tuberculosis and a strain isolated from a patient diagnosed with lung carcinoma. Using this approach, we were able to provide a clear demonstration of laboratory cross-contamination within just four working days. Further epidemiological investigations revealed that the two isolates were processed for culture on the same day.The application of MST has been demonstrated to serve as a rapid and efficient method to investigate cases of possible cross-contamination with M. tuberculosis.The isolation of Mycobacterium tuberculosis complex organisms from clinical specimens collected from suspected patients serves as the gold standard for the proper diagnosis of tuberculosis in the laboratory [1]. However, false-positive cultures have been reported that result from the cross-contamination of specimens via a contaminated bronchoscope [2,3] or, more often, by laboratory cross-contamination [4]. The latter situation has been reported at a frequency ranging from 0.1% to 3% of M. tuberculosis [1,4-8]. Laboratory cross-contamination should be suspected when M. tuberculosis is cultured from a smear-negative specimen processed in the same batch as a culture from a smear-positive specimen. The factors that increase the likelihood of cross-contamination include instances when only one of several specimens from the same patient is culture-positive and instances when the clinician is considering a diagnosis other than tuberculosis, which the clinician believes to be more likely based on clinical observations [8]. Such false-positives resulting from cross-contaminated specimens are disadvantageous since, besides resulting in a misdiagnosis, they result in unnecessary treatment and delay further diagnostic investigations in an effort to derive a definitive and correct diagnosis [9]. Finally, these false-positive cultures lead to an overestimation of the incidence and

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