Tetrazolium reduction allows assessment of biofilm formation byCampylobacter jejuniin a food matrix model

Aims To develop a staining method for specific detection of metabolically active (viable) cells in biofilms of the foodborne pathogen Campylobacter jejuni. Methods and Results Conversion of 2,3,5 triphenyltetrazolium chloride (TTC) to insoluble, red 1,3,5‐triphenylformazan (TPF) was dependent on metabolic activity of Camp. jejuni. When used with chicken juice, TTC staining allowed quantification of Camp. jejuni biofilm levels, whereas the commonly used dye, crystal violet, gave high levels of nonspecific staining of food matrix components (chicken juice). The assay was optimized to allow for monitoring of biofilm levels and adapted to monitor levels of Camp. jejuni in broth media. Conclusions Staining with TTC allows for the quantification of metabolically active Camp. jejuni and thus allows for quantification of viable cells in biofilms and food matrices. The TTC staining method can be adapted to quantify bacterial cell concentration in a food matrix model, where the accepted method of A600 measurement is not suitable due to interference by components of the food matrix