Viable but nonculturable

Journal.pone.0017585.g004

Viable but Nonculturable (VBNC) State refers to a physiological condition in which bacteria are alive but cannot be cultured using standard laboratory techniques. This state is a survival strategy adopted by many bacterial species in response to adverse environmental conditions. The VBNC state has significant implications for public health, food safety, and environmental microbiology, as it may underestimate the presence of pathogenic bacteria in various environments and samples.

Overview

The VBNC state was first described in the 1980s, and since then, it has been observed in a wide range of bacterial species, including important pathogens such as Vibrio cholerae, Escherichia coli, and Salmonella spp.. Bacteria in the VBNC state retain metabolic activity and can revert to a culturable state under favorable conditions, a process known as resuscitation. However, while in the VBNC state, they do not form colonies on standard agar media, making them difficult to detect using conventional microbiological methods.

Induction of the VBNC State

Several environmental stressors can induce the VBNC state, including:

• Temperature extremes (either too high or too low)
• Nutrient starvation
• High salinity
• Exposure to disinfectants and other chemical agents
• Ultraviolet radiation

The specific conditions that trigger the VBNC state vary among bacterial species and strains.

Detection and Implications

The detection of VBNC bacteria poses a challenge for microbiology and public health. Traditional culture-based methods are ineffective, necessitating the use of alternative techniques such as polymerase chain reaction (PCR), flow cytometry, and direct viable count (DVC) methods. The presence of VBNC pathogens in water, food, and environmental samples can lead to underestimation of microbial hazards, potentially leading to outbreaks of foodborne illnesses and waterborne diseases.

Research and Future Directions

Research on the VBNC state aims to better understand the mechanisms of entry into and exit from this state, develop more effective detection methods, and assess the risk posed by VBNC pathogens to human health. Understanding the conditions that allow for the resuscitation of VBNC cells is particularly important for preventing disease transmission.

Conclusion

The VBNC state is a critical concept in microbiology, with significant implications for public health, food safety, and environmental monitoring. Advances in detection methods and a deeper understanding of the VBNC state are essential for accurately assessing the risks posed by pathogenic bacteria in the environment.

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