[Viable non-culturable bacteria].

Abstract

Viable but non-culturable cells (VBNC) are defined as live bacteria, but which do not either grow or divide. Such bacteria cannot be cultivated on conventional media (they do not form colonies on solid media, they do not change broth appearance), but their existence can be proved using other methods. The switch to the VBNC stage has been described and documented for several bacterial species: Vibrio spp. (cholerae, vulnificus and other species), Escherichia coli (including EHEC), Campylobacter jejuni, Helicobacter pylori, Salmonella spp., Listeria monocytogenes, Yersinia enterocolytica, Shigella spp., Klebsiella spp., Enterobacter spp., Cronobacter spp., Staphylococcus aureus, Providencia spp., Morganella spp., Pseudomonas spp., Mycobacterium tuberculosis, Enterococcus spp. The capacity of both Gram-positive and Gram-negative bacteria to enter the VBNC stage started to concern microbiologists in the field of food industry (food and water safety) and pharmaceutical industry. Many studies have shown that processes meant to achieve bactericidal effects can favour bacterial switch to VBNC. Viable but non-culturable stage is reversible. Concerns are due to the capacity of VBNC, especially of potentially pathogen cells, to switch to the infectious stage once in the host organism.