COMPARISON OF PRESERVATION MEDIA FOR STORAGE OF STOOL SAMPLES

Transportation of clinical samples and long-term recoverability of pat hogens are critical to epidemiological studies, particularly when cond itions do not permit immediate processing, This study confirms that Ca ry-Blair medium (CB) is suitable for the preservation of Salmonella an d Shigella isolates for more than 2 weeks: at 25, 4, or -70 degrees C, Campylobacter jejuni was not recovered after 2 days of storage in CB at 25 degrees C when an inoculum of 12 x 10(8) cells per mi was used, Lower temperatures supported the recovery of this organism for 6 days, When individual pathogens were preserved with stools in CB and incuba ted at 25, 4, or -70 degrees C, the Salmonella and Shigella concentrat ions dropped from 12 x 10(8) cells to 1 x 10(3) or 1 x 10(4) cells per mi within 2 days and then remained stable for the rest of the observa tion period (15 days). C, jejuni survived preservation with stools for 5 to 9 days, The addition of blood and glycerol to CB improved the re coverability of all enteropathogens, particularly C. jejuni, which was consistently detected for 7 to 9 days at the different preservation t emperatures used, When trypticase soy broth-glycerol (freezing medium) , with or without blood, was used, there was little or no decrease in the Salmonella and Shigella concentrations during 2 weeks of preservat ion with stools at -70 degrees C, C. jejuni demonstrated a relatively sustained high concentration in Trypticase soy broth-glycerol with 5% blood, The use of defibrinated, laked sheep blood as a long-term freez ing medium supported the recovery of low concentrations of Salmonella and Shigella spp, (10(2) to 10(3) cells per mi) for more than 14 weeks , Recovery of C. jejuni was consistent for 7 weeks when an initial con centration of 10(6) cells per mi was present in stools. Laked blood pr ovided a simple, sterile, and inexpensive medium for the preservation of individual isolates and clinical samples.