Screening of Bacteria from the Cattle Gastrointestinal Tract for Inhibitory Activity against Enterohemorrhagic Escherichia coli O157:H7, O111:H-, and O26:H11

• Published in: Journal of food protection Vol. 69; no. 12; pp. 2843 - 2850
• Main Authors: Gough, J.M, Conlan, L.L, Denman, S.E, Krause, D.O, Smith, W.J.M, Williamson, M.A, McSweeney, C.S
• Format: Journal Article
• Language: English
• Published: United States 01.12.2006
• Subjects: acetic acid; acid tolerance; Animals; antibacterial properties; Antibiosis; bacterial contamination; Bifidobacterium - physiology; cattle; Cattle - microbiology; Colony Count, Microbial; competitive exclusion; DNA, Bacterial - analysis; Enterococcus - physiology; enterohemorrhagic Escherichia coli; Escherichia coli; Escherichia coli - growth & development; Escherichia coli - isolation & purification; Escherichia coli O157 - growth & development; Escherichia coli O157 - isolation & purification; Escherichia coli O157:H7; food contamination; food pathogens; gastrointestinal system; heat tolerance; intestinal microorganisms; lactic acid; lactic acid bacteria; Lactobacillus - physiology; Microbial Sensitivity Tests; Molecular Weight; probiotics; restriction fragment length polymorphism; Ruminantia; screening; Selenomonas - physiology; Serotyping; Streptococcus - physiology
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-69.12.2843

A quick and reproducible microgel plate assay was adapted to screen bacteria from cattle gastrointestinal tracts for production of compounds inhibitory to the growth of three enterohemorrhagic Escherichia coli (EHEC) serotypes: O157:H7, O111:H(-), and 026:H11. The inhibitory activity of 309 bacteria, isolated on several agar media, was assessed by a microgel assay performed in 96-well microtiter plates. Fifty-three isolates secreted inhibitory compounds with a molecular weight of less than 1,000. In 12 isolates, the inhibitory activity was attributable to compounds other than lactic or acetic acid. These compounds were highly heat tolerant, with varying sensitivity to digestion by proteolytic enzymes. The inhibitory isolates were identified as lactic acid-producing bacteria on the basis of a combination of analyses, including 16S-rDNA restriction fragment length polymorphisms, 16S-rDNA gene sequences, and fermentation end products. The lactic acid bacteria of ruminants may contain antibacterial compounds not yet described. Naturally occurring populations of lactic acid bacteria may have potential as probiotics, to reduce the carriage of EHEC in the gastrointestinal tract of ruminants.