Viable but Non-culturable Bacteria: Clinical Practice and Future Perspective

Due to intolerable environmental conditions, bacteria learnt to adopt a useful strategy to survive longer which these organisms generally is termed "viable but non-culturable". In the case of exposure to certain stresses (e.g., antibiotics, low metabolites, heavy metal and high pH environment, etc.), bacteria enter into the VBNC stage. In similar, having the starvation mode of physiology can be called VBNC model. In fact, viable but non-culturable cells (VBNC) are live bacteria, however, they are unable to be cultivated on conventional culture media (1). Because of complexities in culture, observation of normal colonies on solid and broth media is almost impossible for VBNCs. As complexities were observed for successful culture, our clinical practice is in intense lack of a useful present approach to an accurate diagnosis. Basically, the ability to have the VBNC state can help the bacterium to keep the survival chance, but it endangers human health in the case of pathogenic bacteria (2). The first report indicating the clinical relevance of VBNC backs to more than 40 years ago, but still many unanswered questions are left intact (3). The current challenge is that VBNCs are reversible, therefore in many clinical settings, we should have considered them for causing specific infectious diseases. An important issue is that there is no clue that how many cases are indeed reinfections and new infections, whilst we are unable to detect VBNC for many of pathogenic microorganisms. Indeed, there is a long list of bacteria able to enter this dormancy phase. For example, Shigella spp., Helicobacter pylori, Morganella spp., Escherichia coli (including EHEC), Staphylococcus aureus, Listeria monocytogenes, Enterococcus spp., Vibrio spp. (cholera and vulnificus), Yersinia enterocolytica, and Campylobacter jejuni (4-7). As stated, many of infectious agents are initiating diseases which are transmissible and it raises concerns for better hygiene and health policies. Moreover, our diagnostic laboratories should be also sensed to prevent the occurrence of local and national epidemic.