Current Perspectives on Viable but Non-Culturable (VBNC) Pathogenic Bacteria

Abstract

Under stress conditions, many species of bacteria enter into starvation mode of metabolism or a physiologically viable but non-culturable (VBNC) state. Several human pathogenic bacteria have been reported to enter into the VBNC state under these conditions. The pathogenic VBNC bacteria cannot be grown using conventional culture media, although they continue to retain their viability and express their virulence. Though there have been debates on the VBNC concept in the past, several molecular studies have shown that not only can the VBNC state be induced under in vitro conditions but also that resuscitation from this state is possible under appropriate conditions. The most notable advance in resuscitating VBNC bacteria is the discovery of resuscitation-promoting factor (Rpf), which is a bacterial cytokines found in both Gram-positive and Gram-negative organisms. VBNC state is a survival strategy adopted by the bacteria, which has important implication in several fields, including environmental monitoring, food technology, and infectious disease management; and hence it is important to investigate the association of bacterial pathogens under VBNC state and the water/foodborne outbreaks. In this review, we describe various aspects of VBNC bacteria, which include their proteomic and genetic profiles under the VBNC state, conditions of resuscitation, methods of detection, antibiotic resistance, and observations on Rpf.

ColiSense, today's sample today: A rapid on-site detection of β-d-Glucuronidase activity in surface water as a surrogate for E. coli

“…For these reasons it is difficult to correlate the two approaches although this is commonly done due to a lack of a practical alternative standard reference method [9,12,16]. There is a growing body of evidence pointing to the virulence of VBNC bacteria and suggesting the importance of measuring their numbers in environmental waters [17][18][19]. For this purpose enzyme assays are a measurement technology which could be implemented and optimised.…”

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“…The occurrence of VBNC L. pneumophila in water distribution systems may lead to false confidence that the bacteria have been eradicated from the system if presence is determined by a culture method. In other species of bacteria, it has been shown that gene expression can be altered in the VBNC state, typically showing gene supression [129]. However, it has been shown that VBNC cells retain intact genetic material and there are no genetic knockdowns during the VBNC state [130,131].…”

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“…Pure culture method has also been used to detect pathogenic microorganisms. However, a large number of microorganisms and pathogens cannot be detected by pure culture because although they are viable, they are non-culturable [8]. In addition, water-borne microorganisms are characterized by low abundance, diversity, and complexity, which make them difficult to detect.…”