Limiting false-positive polymerase chain reaction results: detection of DNA and mRNA to differentiate viable from dead bacteria.

We compared 2 methods for determining Escherichia coli viability in vitro. A 16S rDNA polymerase chain reaction (PCR) assay detected bacteria irrespective of viability. A groEL mRNA reverse transcriptase PCR was positive for 72 h but later became negative. Detecting mRNA holds promise but is tedious, and groEL may not be the best target.