Inactivation of Escherichia coli O157:H7 in Simulated Human Gastric Fluid

• Published in: Applied and Environmental Microbiology Vol. 71; no. 1; pp. 320 - 325
• Main Author: Tamplin, Mark L
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 2005
• Subjects: Animals; antacids; Antacids - metabolism; Bacteria; bacterial contamination; Bacteriology; Biological and medical sciences; Cattle; Cells; Colony Count, Microbial; cooked ground beef; Culture Media; Disease; Escherichia coli; Escherichia coli O157 - growth & development; Escherichia coli O157:H7; Escherichia infections; Fluids; food contamination; Food Microbiology; food pathogens; foodborne infections; Fundamental and applied biological sciences. Psychology; gastric juice; Gastric Juice - microbiology; ground beef; Humans; Hydrogen-Ion Concentration; inactivation; Meat Products - microbiology; Microbiology; pathogen survival; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; risk assessment; Shigella; Shigella - growth & development; Shigella flexneri; Shigella flexneri - growth & development; simulated gastric fluid; Simulation; Sodium Chloride; Human; Infection; Stomach; Simulation; Escherichia coli; Bacteria; Inactivation; Enterobacteriaceae
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.71.1.320-325.2005

Human disease caused by Escherichia coli O157:H7 is a function of the number of cells that are present at potential sites of infection and host susceptibility. Such infectious doses are a result, in part, of the quantity of cells that are ingested and that survive human host defenses, such as the low-pH environment of the stomach. To more fully understand the kinetics of E. coli O157:H7 survival in gastric fluid, individual E. coli O157:H7 strains were suspended in various media (i.e., saline, cooked ground beef [CGB], and CGB containing a commercial antacid product [CGB+A]), mixed at various proportions with simulated human gastric fluid (SGF), and then incubated at 37°C for up to 4 h. The highest inactivation rate among nine E. coli O157:H7 strains was observed in saline. Specifically, the average survival rates in 100:1 and 10:1 proportions of SGF-saline were -1.344 ± 0.564 and -0.997 ± 0.388 log₁₀ CFU/h, respectively. In contrast, the average inactivation rate for 10 E. coli O157:H7 strains suspended in 10:1 SGF-CGB was -0.081 ± 0.068, a rate that was 12-fold lower than that observed for SGF-saline. In comparison, the average inactivation rate for Shigella flexneri strain 5348 in 100:1 and 10:1 SGF-saline was -8.784 and -17.310, respectively. These latter inactivation rates were 7- to 17-fold higher than those for E. coli O157:H7 strains in SGF-saline and were 4-fold higher than those for E. coli O157:H7 strains in SGF-CGB. The survival rate of E. coli O157:H7 strain GFP80EC increased as the dose of antacid increased from one-half to twice the prescribed dose. A similar trend was observed for the matrix pH over the range of pH 1.6 to 5.7, indicating that pH is a primary factor affecting E. coli O157:H7 survival in SGF-CGB+A. These results can be used in risk assessment to define dose-response relationships for E. coli O157:H7 and to evaluate potential surrogate organisms.