Karmakar, Sushmita and Roychoudhury, K.
Salmonella and Pseudomonas were induced to Viable but Non Culturable state by starvation and temperature up shift to 50°C. The change in osmolarity by addition of more than 10%NaCl also resulted in induction into VBNC state of both Salmonella and Pseudomonas. In the VBNC state these cultures lost their capacity to reduce nitrate. Salmonella also lost the capacity to ferment mannitol, sorbitol, xylose and citrate utilization. On the other hand, for Pseudomonas the capacity to ferment mannitol was lost in VBNC state. While serum and egg yolk could not help the resuscitation of these cultures but favourable temperature between 35°C – 40°C and enrichment of media would help in resuscitation of these cultures. There were distinct differences in the VBNC state with respect to many enzyme activities.
Keywords: Salmonella | Pseudomonas | Culture
Introduction
Bacteria are considered a diverse group and are almost omnipresent in nature. At times conditions may prevail which may not be conducive to the overall well being or growth of the living system. Almost every living system experiences such odd conditions. Bacteria often face conditions that are not conducive to growth and multiplication. This may led to enter into various states which includes the VBNC (Viable but Non Culturable) state. A characteristic of these cells is that, though very much viable and metabolically active, they show a loss of Culturability on routine culture media. Various workers have studied and given evidences of bacteria entering the VBNC state. (Muela et al., 2008, Signoretto et al., 2000, Shleeva et al., 2004, Asakura et al., 2008).
Moreover VBNC state is not a permanent state and the VBNC state organisms can be reverted back to a culturable state. This phenomenon is known as ‘Resuscitation’. Various factors like temperature up shift increase in nutrient concentrations, and supplementation of additional substances and at times presence of host cells can cause resuscitation.
It is observed that the organisms retain their virulence potential upon resuscitation by many workers as in Mycobacterium tuberculosis (Laam li et al., 2014) Legionella sps (Steinert et al., 1997, Al Bama et al., 2013). Vibrio sps. (Baffone et al., 2003, Sun et al., 2008) A number of virulence and toxin genes are expressed even in the VBNC state (Vora et al., 2005). This can be particularly dangerous as the non detected VBNC state cells might gain entry into host body and reasocitate in favourable conditions in the host body causing diseases, the cause of which may remain unknown. Thus it is highly essential to intensely study hundreds of pathogens which may remain in our surroundings in the VBNC state and may well be the cause of recurrent infections.