Comparison of preservation media for storage of stool samples

Abstract

Transportation of clinical samples and long-term recoverability of pathogens are critical to epidemiological studies, particularly when conditions do not permit immediate processing. This study confirms that Cary-Blair medium (CB) is suitable for the preservation of Salmonella and Shigella isolates for more than 2 weeks at 25, 4, or ؊70 C. Campylobacter jejuni was not recovered after 2 days of storage in CB at 25 C when an inoculum of 12 ؋ 10 8 cells per ml was used. Lower temperatures supported the recovery of this organism for 6 days. When individual pathogens were preserved with stools in CB and incubated at 25, 4, or ؊70 C, the Salmonella and Shigella concentrations dropped from 12 ؋ 10 8 cells to 1 ؋ 10 3 or 1 ؋ 10 4 cells per ml within 2 days and then remained stable for the rest of the observation period (15 days). C. jejuni survived preservation with stools for 5 to 9 days. The addition of blood and glycerol to CB improved the recoverability of all enteropathogens, particularly C. jejuni, which was consistently detected for 7 to 9 days at the different preservation temperatures 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 preservation with stools at ؊70 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 freezing medium supported the recovery of low concentrations of Salmonella and Shigella spp. (10 2 to 10 3 cells per ml) for more than 14 weeks. Recovery of C. jejuni was consistent for 7 weeks when an initial concentration of 10 6 cells per ml was present in stools. Laked blood provided a simple, sterile, and inexpensive medium for the preservation of individual isolates and clinical samples.

Preliminary biomedical evaluation of wild ruffed lemurs (Varecia variegata and V. rubra)

“…Bacteria that are commonly considered pathogenic in primates (Salmonella, Shigella, Campylobacter, and Yersinia) were not detected, supporting the assumption that they are not part of the normal enteric flora. Although storage of feces without cryoprotectant in liquid nitrogen has been shown to be effective for sustaining the viability of enteric bacteria [Dan et al, 1989], other studies have suggested that the addition of freezing mediums enhances the recovery of enteropathogens, especially Campylobacter [Wasfy et al, 1995]. Therefore, we cannot state that these agents are not present in wild lemurs.…”

“…Approximately 1 cc of feces was placed into the transport medium (ParaPak; Meridian Diagnostics, Cincinnati, OH) for examination for parasite ova. If sufficient feces were obtained, a second 1-cc sample was frozen (without cryoprotectant) in liquid nitrogen for bacterial culture [Dan et al, 1989;Wasfy et al, 1995].…”

Faecal microbiota transplant for recurrentClostridium difficileinfection using long-term frozen stool is effective: clinical efficacy and bacterial viability data

“…27 The reduced viability of organisms stored in phosphate buffered glycerol saline in that study may have in part been due to the storage temperature of À20°C rather than À80°C, because it has been demonstrated that lower temperatures enhance bacterial survival. 26 Cryopreserving media such as Cary-Blair media, skim milk and Amies media, have been used to store stool for later analysis [29][30][31] , however, some of these media are less effective than 10% glycerol solutions at retaining microbial viability and others are unsuitable to be administered into a patient's gastrointestinal tract as they are untested on humans.…”

A simple technique for long‐term preservation of leptospires

“…Since the addition of blood as a cryopreservant is useful due to the presence of some factors contributing to the buffering, osmotic, homeostatic, and cryoprotective properties which are necessary for the survival of certain bacteria , sheep blood was used in the present study. However, unforeseen findings have been noticed.…”