title: Optimising the viability during storage of freeze-dried cell preparations of Campylobacter jejuni.
abstract: Freeze-dried cultures of Campylobacter jejuni are used in the food and microbiological industry for reference materials and culture collections. However, C. jejuni is very susceptible to damage during freeze-drying and subsequent storage and it would be useful to have longer-lasting cultures. The survival of C. jejuni during freeze-drying and subsequent storage was investigated with the aim of optimising survival. C. jejuni was freeze-dried using cultures of different age (24-120 h), various lyoprotectants (10% phytone peptone, proteose peptone, peptonized milk, trehalose, soytone and sorbitol), various storage (air, nitrogen and vacuum) and re-hydration (media, temperature and time) conditions. One-day-old cultures had significantly greater survival after freeze-drying than older cultures. The addition of trehalose to inositol broth as a lyoprotectant resulted in almost 2 log(10) increase in survival after 2 months storage at 4 degrees C. Storage in a vacuum atmosphere and re-hydration in inositol broth at 37 degrees C increased recovery by 1-2 log(10) survival compared to re-hydration in maximal recovery diluent (MRD) after storage at 4 degrees C. Survival during storage was optimal when a one-day-old culture was freeze-dried in inositol broth plus 10% (w/v) trehalose, stored under vacuum at 4 degrees C and re-hydrated at the same incubation temperature (37 degrees C) in inositol broth for 30 min. The results demonstrate that the survival of freeze-dried cells of C. jejuni during storage can be significantly increased by optimising the culture age, the lyoprotectant, and the storage and re-hydration conditions. The logarithmic rate of loss of viability (K) followed very well an inverse dependence on the absolute temperature, i.e., the Arrhenius rate law. Extrapolation of the results to a more typical storage temperature (4 degrees C) predicted a very low K value of 1.5 x 10(-3). These results will be useful to the development of improved reference materials and samples held in culture collections.
authors.affiliation: Central Science Laboratory, Sand Hutton, York, YO41 1LZ, UK.
authors.forename: Daniella C
authors.initials: DC
authors.lastname: Portner
authors.forename: Renata G K
authors.initials: RG
authors.lastname: Leuschner
authors.forename: Brent S
authors.initials: BS
authors.lastname: Murray
mesh_terms: D016123:Campylobacter jejuni / Q000187:drug effects / Q000502:physiology*; D003451:Cryoprotective Agents / Q000494:pharmacology; D005612:Freeze Drying / Q000379:methods*; D007294:Inositol / Q000494:pharmacology; D050296:Microbial Viability; D010461:Peptones / Q000494:pharmacology; D013012:Sorbitol / Q000494:pharmacology; D014199:Trehalose / Q000494:pharmacology
chemical_list: D003451:Cryoprotective Agents; D010461:Peptones; D007294:Inositol; D013012:Sorbitol; D014199:Trehalose