mRNA detection by reverse transcription-PCR for monitoring viability over time in an Enterococcus faecalis viable but nonculturable population maintained in a laboratory microcosm

The viable but nonculturable (VBNC) state is a survival strategy adopted by bacteria when they are exposed to hostile environmental conditions. It has been shown that VBNC forms of bacteria are no longer capable of growing on conventional bacteriological media but conserve pathogenic factors and/or genes. It is thus necessary to develop methods capable of detecting noncult urable bacteria and of establishing their viability when the microbiologica l quality of environments is monitored. In this study we demonstrated that a gene was expressed during the VBNC state in a low-nutrient-concentration microcosm through detection of Enterococcus faecalis pbp5 mRNA by reverse t ranscription-PCR over a 3-month period. The presence of mRNA correlated wit h metabolic activity and resuscitation capability, indicating the viability of the VBNC cells.