The Viable but Nonculturable Concept, Bacteria in Urine Samples, and Occam's Razor

Discrepancies between the number of bacterial cells that can be detected by a direct counting method such as microscopy and the number that form colonies on standard media are regularly reported and extensively discussed (3). The observations of Anderson and colleagues concerning urine specimens (1) fall into this category and are without doubt of considerable interest and potential importance. The intriguing conclusion that there is an abundant source of nonculturable prokaryotic cells in the urinary tracts of humans and mice seems unavoidable. However, we are concerned that the title of the paper and the assumption that the bacteria detected were in the viable but nonculturable (VBNC) state is not justified by either those authors' data or the preceding literature. In particular, the implication that the cell populations termed VBNC by Anderson et al. are in a specific physiological state distinct from starvation is highly contentious and potentially misleading.