Use of multiparameter analysis for Vibrio alginolyticus viable but nonculturable state determination

Vibrio alginolyticus is known to enter into a viable but nonculturable (VBNC) state in response to environmental conditions unfavorable to the growth. Cells in VBNC condition pose a public health threat because they are potentially pathogenic.

We constructed a pathway for the identification of the most significant variables and the characterization of those variables able to discriminate the groups under investigation. Different parameters measured by the image processing software were chosen as the most representative of V. alginolyticus cell morphology (length index for dimension) and metabolic activity (density profile indexes). To detect relationships between the groups of treatment performed, we carried out a principal components analysis (PCA).

The PCA analysis indicated that increasing coccoid shape transformation was related to both metabolic and dimension variations, delineating a well defined graph profile. Indeed, we discovered that specific morphological variations occur when cells in the culturable state pass into VBNC condition, namely comma-shaped culturable bacteria are converted into coccoid-shaped VBNC cells. The results were also supported by scanning electron microscopy analysis.

This technique allows the analysis of a large number of vibrio samples in a short period of time. The obtained multiparameter information may complement genetic/molecular analyses facilitating, in an automatic fashion, further studies to evaluate the potential risk of this pathogen in the environment. It may also be a useful tool for large-scale cell biology studies and high content screening.