Environmental desiccation stress induces viable but non culturable state in Neisseria meningitidis.

Environmental factors play a crucial role in bacterial virulence. During transmission, in a non-host environment bacteria are exposed to various environmental stress which could alter bacterial physiology and virulence. N. meningitidis is transmitted from person to person through direct contact. However, the role of environmental desiccation in the virulence of bacterial pathogens is not clearly understood. Therefore, the effect of environmental desiccation on survival, transmission, and virulence needs further investigation. We demonstrate that N. meningitidis was sensitive to desiccation stress. The viable counts reduced significantly (p < 0.05) after desiccation. It was found that desiccation induces a viable but non-culturable state (VBNC) in N. meningitidis. We considered cells to be in VBNC when no viable counts were obtained on growth media and live cells were detected after live-dead staining. After resuscitation, N. meningitidis retained virulence characteristics which indicate that it can transit between the host in VBNC state. Furthermore, the relative expression of capsule increased significantly after 12 and 24 h of desiccation. The observations indicate that the environmental desiccation might induce capsule biosynthesis in N. meningitidis, leading to enhanced virulence and survival in macrophages.