How dead is dead? Viable but non‐culturable versus persister cells

Editorial: Emerging Frontiers in the Formation of Viable but Non-culturable Microorganisms and Biofilms During Food Processing

“…The term VBNC has perfectly described a specific microbial cellular state when a cell is not culturable but still viable which is metabolically alive and has potential to resuscitate back to culturable. We strongly agree with Kirschner et al (2021) on the definition of VBNC, which was firstly proposed by Oliver (2010), as "A bacterial cell in the VBNC state may be defined as one which fails to grow at the routine bacteriological cultivation conditions under which it would normally grow, but which in fact is alive and has still metabolic activity." Song et al had argued that "By inactivating their ribosomes, persister cells sleep through stress and resuscitate once (i) the stress is removed, (ii) nutrients are presented, and (iii) ribosome content reaches a threshold.…”

“…Not surprisingly, a few opposing comments/opinions had been posed subsequently, as firstly a correspondence entitled "How dead is dead? Viable but non-culturable vs. persister cells" by Kirschner et al (2021), with a later response from the original authors entitled "Waiting for Godot: response to 'How dead is dead? Viable but non-culturable vs. persister cells" (Song and Wood, 2021c); secondly another correspondence entitled "What do we mean by viability in terms of "viable but non-culturable" cells?"…”

A Multi-Purpose Approach to the Mechanisms of Action of Two Biocides (Benzalkonium Chloride and Dibromonitrilopropionamide): Discussion of Pseudomonas fluorescens’ Viability and Death

“…Over the past two decades, many researchers have been discussing that cells can reach the viable but non-culturable (VBNC) state as a mechanism of defense and self-preservation (Keep et al, 2006;Alam et al, 2007;Li et al, 2014;Emerson et al, 2017;Fleischmann et al, 2021;Kirschner et al, 2021). Cells enter the VBNC state when submitted to harsh stress conditions (Highmore et al, 2018; exposure to biocides/antibiotics, temperature shifts, lack of nutrients).…”

“…Cells enter the VBNC state when submitted to harsh stress conditions (Highmore et al, 2018; exposure to biocides/antibiotics, temperature shifts, lack of nutrients). The more usual characterization of cells that enter the VBNC state is: (i) they retain their membrane integrity; (ii) they are still metabolically active (reduced levels of metabolic activity); (iii) they are able to produce proteins; but (iv) they are not able to grow on solid media (Oliver, 2010;Ayrapetyan et al, 2014Ayrapetyan et al, , 2018Fleischmann et al, 2021;Kirschner et al, 2021). Also, VBNC cells are more chemically and physiologically resistant than culturable cells (Signoretto et al, 2000;Li et al, 2014), making them a major threat in many areas, including public health.…”

“…Thus, the use of the most appropriate viability marker should be further discussed when determining VBNCs. Nonetheless, Kirschner et al (2021) also pointed out that care must be taken when quantifying VBNC cells, especially when such quantification is based on a single viability parameter analysis. Alternatively, a double staining procedure with 4,6-di-amidino-2-phenylindole (DAPI) and tetrazolium salt 5-cyano-2,3-ditolyltetrazolium chloride (CTC) could be used to discriminate VBNC cells (Besnard et al, 2000;Fleischmann et al, 2021).…”