In vitro inactivation of Escherichia coli O157:H7 in bovine rumen fluid by caprylic acid

• Published in: Journal of food protection Vol. 67; no. 5; pp. 884 - 888
• Main Authors: Annamalai, T, Nair, M.K.M, Marek, P, Vasudevan, P, Schreiber, D, Knight, R, Hoagland, T, Venkitanarayanan, K
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association of Milk, Food and Environmental Sanitarians 01.05.2004
• Subjects: anaerobes; Animal productions; Animals; Anti-Infective Agents - pharmacology; antibacterial properties; Bacteria, Anaerobic - drug effects; Bacteria, Anaerobic - growth & development; bacterial contamination; beef cattle; Biological and medical sciences; Caprylates - pharmacology; Cattle; Colony Count, Microbial; culture media; Dose-Response Relationship, Drug; Escherichia coli; Escherichia coli O157 - drug effects; Escherichia coli O157 - growth & development; Escherichia coli O157:H7; feed supplements; food contamination; food pathogens; food safety; food-grade chemical; Fundamental and applied biological sciences. Psychology; GRAS substances; Hydrogen-Ion Concentration; in vitro studies; inactivation; minimum inhibitory concentration; octanoic acid; pathogen survival; plate count; Rumen - microbiology; rumen fluids; structured lipids; Temperature; Terrestrial animal productions; Vertebrates; Bovine; Digestive system; Escherichia coli; Rumen; Veterinary medicine; Inactivation; In vitro; Octanoic acid; Prevention; Vertebrata; Mammalia; Bacteria; Artiodactyla; Supplementation; Slaughter; Ungulata; Enterobacteriaceae
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-67.5.884

The antibacterial effect of caprylic acid (35 and 50 mM) on Escherichia coli O157:H7 and total anaerobic bacteria at 39°C in rumen fluid (pH 5.6 and 6.8) from 12 beef cattle was investigated. The treatments containing caprylic acid at both pHs significantly reduced (P < 0.05) the population of E. coli O157:H7 compared with that in the control samples. At pH 5.6, both levels of caprylic acid killed E. coli O157:H7 rapidly, reducing the pathogen population to undetectable levels at 1 min of incubation (a more than 6.0-log CFU/ml reduction). In buffered rumen fluid at pH 6.8, 50 mM caprylic acid reduced the E. coli O157:H7 population to undetectable levels at 1 min of incubation, whereas 35 mM caprylic acid reduced the pathogen by approximately 3.0 and 5.0 log CFU/ml at 8 and 24 h of incubation, respectively. At both pHs, caprylic acid had a significantly lesser (P < 0.05) and minimal inhibitory effect on the population of total anaerobic bacteria in rumen compared with that on E. coli O157:H7. At 24 h of incubation, caprylic acid (35 and 50 mM) reduced the population of total anaerobic bacteria by approximately 2.0 log CFU/ml at pH 5.6, whereas at pH 6.8, caprylic acid (35 mM) did not have any significant (P > 0.05) inhibitory effect on total bacterial load. Results of this study revealed that caprylic acid was effective in inactivating E. coli O157:H7 in bovine rumen fluid, thereby justifying its potential as a preslaughter dietary supplement for reducing pathogen carriage in cattle.