The viable but non-culturable state in pathogenic <i>Escherichia coli</i>: A general review

Abstract

BackgroundThe persistence and pathogenicity of pathogenic bacteria are dependent on the ability of the species to survive in adverse conditions. During the infectious process, the organism may need to pass through certain hostile anatomical sites, such as the stomach. Under various environmental stresses, many bacteria enter into the viable but non-culturable (VBNC) state, where they are ‘alive’ or metabolically active, but will not grow on conventional media. Escherichia coli bacteria encounter several diverse stress factors during their growth, survival and infection and thus may enter into the VBNC state.ObjectivesThis review discusses various general aspects of the VBNC state, the mechanisms and possible public health impact of indicator and pathogenic E. coli entering into the VBNC state.MethodA literature review was conducted to ascertain the possible impact of E. coli entering into the VBNC state.ResultsEscherichia coli enter into the VBNC state by means of several induction mechanisms. Various authors have found that E. coli can be resuscitated post-VBNC. Certain strains of pathogenic E. coli are still able to produce toxins in the VBNC state, whilst others are avirulent during the VBNC state but are able to regain virulence after resuscitation.ConclusionPathogenic and indicator E. coli entering into the VBNC state could have an adverse effect on public health if conventional detection methods are used, where the number of viable cells could be underestimated and the VBNC cells still produce toxins or could, at any time, be resuscitated and become virulent again.

Characterization of Microbial Signatures From Advanced Treated Wastewater Biofilms

“…Culture‐based methods are limiting because they can identify only those microorganisms that can be grown; usually only indicator bacteria are grown using selective media. Microorganisms that are viable but nonculturable are also not identified by culture‐based methods, generally resulting in an underestimation of their concentration (Pienaar et al 2016, Zhang et al 2015, Li et al 2014, Ramamurthy et al 2014). Methods based on polymerase chain reaction are faster but target only a limited number of organisms and genetic markers (Kitajima et al 2014).…”

Survey of verotoxin-producing Escherichia coli and faecal coliforms in beef carcasses destined for export at slaughterhouses in Brazil

“…Another hypothesis is a low pathogen's inoculum size, hindering the growth on an agar plate (Vallières et al, 2013). Also, many bacterial species develop a viable but non-culturable (VBNC) state, characterized by a loss of culturability, therefore impairing their detection by conventional plate count techniques (Li et al, 2014;Pienaar et al, 2016;Ding et al, 2017). Nevertheless, Stx1 production was detected VBNC cells, pointing out the potential health risk of VBNC E. coli O157:H7 (Liu et al, 2010).…”

Toxin–Antitoxin Systems and their Role in Maintaining the Pathogenic Potential of Causative Agents of Sapronoses

“…Depending on the type of genetic organization, the characteristics of the antitoxin, and the mechanism of its interaction with the toxin, six types of TAS modules are currently identified [35] (Table). In all the TAS types, toxins are represented by proteins, whereas antitoxins can be either a non-translated antisense RNA (types I and III) or a labile protein (types II, IV-VI) [19,35,36]. The best characterized are type I and type II modules.…”