Survival of Listeria monocytogenes in Artificial Seawater

Abstract

The survival of Listeria monocytogenes IID 581 was determined in filtered sterilized artificial seawater (ASW), natural seawater (NSW) and ultra pure water (UPW) microsoms. L. monocytogenes IID581 maintained the culturable state longer at lower temperature in ASW and NSW. However, the pathogen lost culturability in UPW rapidly at all temperatures examined (5, 10 and 30°C).
The culturability of L. monocytogenes IID 581 cells was determined by spread plate count (TSAYE), and the cell activity was observed under a fluorescence microscope, using the LIVE/DEAD BacLight^TM bacteria viability kit. There were significant differences between the results obtained from those two methods at all temperatures (10, 20 and 30°C) in ASW. Greater differences were seen between the above two methods in ASW at higher temperature, while there was little difference between them in UPW. The results indicate that L. monocytogenes IID581 enters a viable but non-culturable (VBNC) state in ASW and both temperature and the concentration of inorganic salts influence the transition to the VBNC state.