The effects of storage conditions on the viability of enteropathogenics bacteria in biobanking of human stools: Cases of Yersinia enterocolitica, Salmonella enterica Typhimurium and Vibrio cholerae O: 1

Abstract

Long-terms recoverability of enteropathogens is necessary for future epidemiological studies to screen stool samples when conditions do not permit immediate processing. The aim of this study was to determine the viability and the recoverability of three enteropathogens bacteria (Yersinia enterocolitica, Vibrio cholerae O: 1 and Salmonella enterica Typhimurium) artificially contaminated at 107 CFU/ml in human stool samples after our storage conditions. Preservations media used were saline, phosphate buffered saline (PBS) and Modified PBS without glycerol and containing 10 and 20% glycerol at three temperatures (4, -20 and -80°C). The viabilities and the recoverabilities of these strains were determined (weekly and monthly) respectively by plating onto tryptic soy agar and detection from artificial inoculated stools samples onto specifics agars. Bacteria populations decreased by 1-5 log10 CFU/ml depending on the strains tested, on the preservation media, on the glycerol concentration and the storage condition. The greatest population decrease was observed in the first week of storage at +4°C and freezing at -20°C and a slow decline in survival occurred thereafter. No organisms were recovered after one month from samples at these temperatures. When samples were subjected to storage at -80°C, all enteropathogenics bacterial were recovered after nine months storage.

Keys words: Biobanking, enteropathogenics bacteria, storage conditions, preservation media, Côte d’Ivoire.