title: In vitro inactivation of Escherichia coli O157:H7 in bovine rumen fluid by caprylic acid.
abstract: The antibacterial effect of caprylic acid (35 and 50 mM) on Escherichia coli O157:H7 and total anaerobic bacteria at 39 degrees 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.
authors.affiliation: Department of Animal Science, Unit 4040, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: Thirunavukkarasu
authors.initials: T
authors.lastname: Annamalai
authors.forename: Manoj Kumar
authors.initials: MK
authors.lastname: Mohan Nair
authors.forename: Patrick
authors.initials: P
authors.lastname: Marek
authors.forename: Pradeep
authors.initials: P
authors.lastname: Vasudevan
authors.forename: David
authors.initials: D
authors.lastname: Schreiber
authors.forename: Randall
authors.initials: R
authors.lastname: Knight
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoagland
authors.forename: Kumar
authors.initials: K
authors.lastname: Venkitanarayanan
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001421:Bacteria, Anaerobic / Q000187:drug effects / Q000254:growth & development; D002210:Caprylates / Q000494:pharmacology*; D002417:Cattle; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D012417:Rumen / Q000382:microbiology*; D013696:Temperature
chemical_list: D000890:Anti-Infective Agents; D002210:Caprylates; C031492:octanoic acid