AMPLIFICATION OF RESIDUAL DNA-SEQUENCES IN STERILE BRONCHOSCOPES LEADING TO FALSE-POSITIVE PCR RESULTS

PCR has been used successfully for the direct detection of Mycobacteri um tuberculosis in uncultured patient samples, Its potential is hinder ed by the risk of false-positive results as a result of either amplico n carryover or cross contamination between patient samples, In the pre sent study, we investigated whether residual amplifiable human or M. t uberculosis 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 c ollected eluate was submitted for PCR amplification of IS6110 sequence s 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 fi ndings indicate that residual DNA can remain in sterilized bronchoscop es and can be a source of false-positive PCR results.