Amplification of residual DNA sequences in sterile bronchoscopes leading to false-positive PCR results

PCR has been used successfully for the direct detection of Mycobacterium tuberculosis in uncultured patient samples, Its potential is hindered by the risk of false-positive results as a result of either amplicon carryover or cross contamination between patient samples, In the present study, we investigated whether residual amplifiable human or M. tuberculosis DNA could remain in sterile bronchoscopes and potentially be a cause of false-positive PCR results in subsequent patient samples, Sterilized bronchoscopes were flushed with sterile saline, and the collected eluate was submitted for PCR amplification of IS6110 sequences and exon 8 of the human p53 gene. Of a total of 55 washes of sterile bronchoscopes from two institutions, 2 (3.6%) contained amplifiable M. tuberculosis DNA and 11 (20%) contained residual human DNA, These findings indicate that residual DNA can remain in sterilized bronchoscopes and can be a source of false-positive PCR results.