Campylobacter jejuni biofilm cells become viable but non-culturable (VBNC) in low nutrient conditions at 4 °C more quickly than their planktonic counterparts

Abstract

Abstract Campylobacter jejuni remains the leading cause of foodborne disease in the developed world. In order to assess the ability of biofilm cells to enter and survive in a viable but non-culturable state, biofilm and planktonic cells of three strains of C. jejuni were incubated at 4 °C in phosphate buffered saline. Culturability was monitored by standard drop plating on Mueller Hinton agar and viability was measured using the LIVE/DEAD® BacLight™ assay which assesses membrane integrity. Both biofilm and planktonic cells became non-culturable prior to becoming non-viable. Biofilm cells became non-culturable as early as 10 days for one strain, while planktonic cells became non-culturable after 30–40 days of treatment. Planktonic cells were still viable after 60 days of stress treatment. Biofilm cells showed significantly reduced viability by day 50 for the two clinical isolates and by day 60 for the poultry isolate. Of the media assessed for their ability to extend the culturability of the VBNC cells, Campylobacter Agar Base with the addition of Campylobacter Growth Supplement was most successful at prolonging culturability, but even with enrichment in Bolton broth, cells still remained viable and potentially infectious, longer than they were culturable.