engleski

Assessment of viability of stressed Campylobacter jejuni cells by plate count and fluorescence techniques

There is an increasing interest in development of new and improvement of existing methods for microbial viability determination. Widely accepted culture based methods underestimate the real viable portion of microbial population, especially when microorganisms are exposed to environmental stresses resulting in sublethal injuries and transformation into the viable but not-culturable cells (VBNC). We compared three different techniques (plate CFU count, fluorescent microscopy, flow cytomety analysis) for assessment of culturability and viability of Campylobacter jejuni after exposure to oxidative stress. Exposure to atmosphere oxygen resulted in a progressive decline of culturability of C. jejuni. A good correlation between culturability and viability, assessed by LIVE/DEAD(R) BacLightTM staining and subsequent fluorescent microscopy, was verified. After 15 hours exposure to oxidative stress, flow cytometry analysis revealed an unknown cell population located within the live and dead bacterial communities, which could be analogous to VBNC cells. Traditional culture based technique confirmed to be satisfactory for detection of viable bacteria but not efficient for non-culturable microorganisms. The adventages of fluorescence microscopy are that it is rapid and allow morphological analysis. Flow cytometry enables additionally to detect different cell populatoins within a microbial community. All methods do have their own limitations and will be further discussed.

Campylobacter; viability; VBNC; fluorescence techniques; microbial stress response

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