Ability of Shiga Toxin-Producing Escherichia coli and Salmonella spp. To Survive in a Desiccation Model System and in Dry Foods

Author:

Hiramatsu Reiji1,Matsumoto Masakado1,Sakae Kenji1,Miyazaki Yutaka1

Affiliation:

1. Aichi Prefectural Institute of Public Health, 7-6 Nagare Tsuji-machi, Kita-ku, Nagoya 462-8576, Japan

Abstract

ABSTRACT In order to determine desiccation tolerances of bacterial strains, the survival of 58 diarrheagenic strains (18 salmonellae, 35 Shiga toxin-producing Escherichia coli [STEC], and 5 shigellae) and of 15 nonpathogenic E. coli strains was determined after drying at 35°C for 24 h in paper disks. At an inoculum level of 10 7 CFU/disk, most of the salmonellae (14/18) and the STEC strains (31/35) survived with a population of 10 3 to 10 4 CFU/disk, whereas all of the shigellae (5/5) and the majority of the nonpathogenic E. coli strains (9/15) did not survive (the population was decreased to less than the detection limit of 10 2 CFU/disk). After 22 to 24 months of subsequent storage at 4°C, all of the selected salmonellae (4/4) and most of the selected STEC strains (12/15) survived, keeping the original populations (10 3 to 10 4 CFU/disk). In contrast to the case for storage at 4°C, all of 15 selected strains (5 strains each of Salmonella spp., STEC O157, and STEC O26) died after 35 to 70 days of storage at 25°C and 35°C. The survival rates of all of these 15 strains in paper disks after the 24 h of drying were substantially increased (10 to 79 times) by the presence of sucrose (12% to 36%). All of these 15 desiccated strains in paper disks survived after exposure to 70°C for 5 h. The populations of these 15 strains inoculated in dried foods containing sucrose and/or fat (e.g., chocolate) were 100 times higher than those in the dried paper disks after drying for 24 h at 25°C.

Publisher

American Society for Microbiology

Subject

Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology

Reference25 articles.

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5. Centers for Disease Control and Prevention. 2004. Outbreak of Salmonella serotype Enteritidis infections associated with raw almonds—United States and Canada, 2003-2004. Morb. Mortal. Wkly. Rep.53:484-487.

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