Fate of Escherichia coli during Ensiling of Wheat and Corn

Abstract

A recombinant Escherichia coli strain carrying a plasmid with an antibiotic resistance marker and expressing the green fluorescent protein was inoculated at a concentration of 3.8 ؋ 10 8 CFU/g into direct-cut wheat (348 g of dry matter kg ؊1 ), wilted wheat (450 g of dry matter kg ؊1 ), and corn (375 g of dry matter kg ؊1 ). The forages were ensiled in mini-silos. The treatments included control (no E. coli added), application of tagged E. coli, and delayed sealing of the inoculated wheat. Three silos per treatment were sampled on predetermined dates, and the numbers of E. coli were determined on Chromocult TBX medium with or without kanamycin. Colonies presumptively identified as E. coli were also tested for fluorescence activity. Addition of E. coli at the time of ensiling resulted in a more rapid decrease in the pH but had almost no effect on the chemical composition of the final silages or their aerobic stability. E. coli disappeared from the silages when the pH decreased below 5.0. It persisted longer in silages of wilted wheat, in which the pH declined more slowly. Control silages of all crops also contained bacteria, presumptively identified as E. coli, that were resistant to the antibiotic, which suggests that some epiphytic strains are naturally resistant to antibiotics.

Fate of Escherichia coli O26 in Corn Silage Experimentally Contaminated at Ensiling, at Silo Opening, or after Aerobic Exposure, and Protective Effect of Various Bacterial Inoculants

“…This preventive measure could also be applied for limiting the presence of E. coli. Although the elimination of E. coli or E. coli O157 during the storage period in corn and grass silage was demonstrated previously in other studies (4,8,12,49), only Pedroso et al investigated the fate of E. coli O157:H7 in silage during the unloading phase (49), as this serotype was the one most frequently associated with outbreaks. Strains of other serogroups, and especially O26, have been increasingly linked to diarrheal disease, but no information regarding the survival and behavior of pathogenic E. coli strains belonging to O26 or other serogroups was available at the time.…”

Sensitivity ofMycobacterium aviumsubspparatuberculosis,Escherichia coliandSalmonella entericaserotype Typhimurium to low pH, high organic acids and ensiling

“…Silage is a valuable source of nutrients for dairy and beef cattle; its importance is increasing with intensification of livestock production (Chen et al . ; McEniry et al . ; Duniére et al .…”

“…In the ensiling process, anaerobic fermentation of forage materials by LAB results in the production of large amounts of OA which rapidly reduce pH, thereby eliminating most unwanted organisms and preserving the material (Chen et al . ; Stevenson et al . ; McEniry et al .…”

“…The ensiling process is used to preserve livestock feed via anaerobic fermentation of water‐soluble carbohydrates by lactic acid bacteria (LAB) (Chen et al . ; Stevenson et al . ; Duniére et al .…”

Management Strategies for Optimizing Forage Quality for Dairy Production

“…Heterolactic inoculants contain bacteria such as Lactobacillus buchneri , the genus Enterobacter is Escherichia coli O157:H7. Silage can be contaminated with the pathogen via manure or irrigation water (Weinberg et al, 2004 ), but the pathogen is usually eliminated when the pH drops below 4 -5 during ensiling (Bach et al, 2002 ;Chen et al, 2005 ;Pedroso et al, 2010 ). However, high pH during silage feedout may encourage its growth (Reinders et al, 1999 ;Queiroz et al, 2009 ).…”