ABSTRACT
Recent years have seen an upsurge of information concerning the phenom enon first described by our laboratory in the late 1970s and early 1980s, namely, the ability of gram-negative bacteria not otherwise able to form spores to undergo a dormancy whereby the cells remain viable and actively metabolizing but not able to be cultured by routine bacteriological methods. Subsequent to the original observations of the ability to detect such cells in the environment and in food, water, and clinical specimens, we have carried out studies showing that pathogenic organisms, such as Sal monella and Shigella species, remain potentially pathogenic and, in the case of the latter, continue to produce toxin. Such cells in large numbers can potentially be a serious public health hazard as evidenced by human volun teer studies done with viable but nonculturable Vibrio cholerae 01. It is important in detecting these viable but nonculturable cells to recognize that the cells remain intact, able to take up substrate and metabolize substrate detectably. Thus, the use of fluorescent antibody probes, as well as gene probes and polymerase chain reaction (PCR), makes it possible to detect and quantitate such cells in a variety of samples. This phenomenon and
these techniques render the standard plate counting procedures unreliable in ensuring the safety of food and water for public consumption. Methods for the detection of pathogenic microorganisms will need to be revised to take into account the phenomenon of the dormant but non-spore-forming bacteria.
