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Effects of the dicarboxylic acids malate and fumarate on E. coli O157:H7 and Salmonella enterica typhimurium populations in pure culture and in mixed ruminal microorganism fermentations.

Abstract：

:The dicarboxylic acids malate and fumarate increase ruminal pH, reduce methane production, increase propionate and total volatile fatty acid (VFA) production, and reduce lactic acid accumulation in a manner similar to ionophores. These acids stimulate the ruminal bacterium Selenomonas ruminantium to ferment lactate to produce propionate. Thus, dicarboxylic acids have been suggested as nonantibiotic modifiers of the ruminal fermentation, but their impact on ruminal microbial ecology remains unknown. This study was designed to examine what effects these modifiers may have on intestinal pathogen populations such as Escherichia coli O157:H7 and S. enterica Typhimurium prior to their widespread incorporation into cattle rations. Pure cultures of E. coli O157:H7 strain 933 and S. enterica Typhimurium were grown with malate and fumarate added at 0, 1, 5, 10, and 20 mM (v/v; n = 3). Neither dicarboxylic acid inhibited (p > 0.1) the growth rate or final populations of E. coli O157:H7 or S. enterica Typhimurium. Ruminal fluid was collected from cattle (n = 2) and E. coli O157:H7 and S. enterica Typhimurium were added to separate ruminal fermentations incubated for 24 h at 39 degrees C. Fumarate and malate were added at concentrations of 0, 5, 10, and 20 mM (v/v; n = 2) and incubated for 24 h at 39 degrees C. Malate or fumarate addition did not affect (p > 0.1) populations of E. coli O157:H7 or S. enterica Typhimurium. However, the final pH was increased (p < 0.05), the acetate:propionate ratio was decreased (p < 0.05), and the total VFA production was increased (p < 0.05) by > or =10 mM dicarboxylic acid addition. These results confirm that dicarboxylic acids can modify ruminal fermentation, but they do not affect populations of critical foodborne pathogens.

journal_name

Curr Microbiol

journal_title

Current microbiology

authors

Nisbet DJ,Callaway TR,Edrington TS,Anderson RC,Krueger N

doi

10.1007/s00284-008-9351-1

subject

Has Abstract

pub_date

2009-05-01 00:00:00

pages

488-92

issue

eissn

0343-8651

issn

1432-0991

journal_volume

pub_type

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Effects of the dicarboxylic acids malate and fumarate on E. coli O157:H7 and Salmonella enterica typhimurium populations in pure culture and in mixed ruminal microorganism fermentations.