Influence of pH treatments on survival of Escherichia coli O157:H7 in continuous cultures of rumen contents

Effect of bedding materials on concentration of odorous compounds and in beef cattle bedded manure packs

The objectives of this study were to determine the effect of bedding material (corn stover, soybean stover, wheat straw, switchgrass, wood chips, wood shavings, corn cobs, and shredded paper) on concentration of odorous volatile organic compounds (VOC) in bedded pack material and to determine the effect of bedding material on the levels of total in laboratory-scaled bedded manure packs. Four bedded packs of each bedding material were maintained for two 6-wk periods ( = 64). Straight- and branched-chained fatty acids and aromatic compounds were measured. Corn cob bedding had the highest concentration of odorous VOC, and wood shavings had the lowest ( < 0.01). Calculated odor activity values were highest for corn cob bedding and shredded paper and lowest for wood shavings ( < 0.01). concentrations decreased from week to week for all treatments from Week 2 to Week 6. At Week 6, levels in bedded packs with shredded paper were higher ( < 0.05) than bedded packs containing wood shavings, wood chips, or switchgrass ( < 0.05). At Weeks 4, 5, and 6, concentrations in bedded packs with wood shavings were lower ( < 0.05) than bedded packs of all treatments except wood chips. Results of this study indicate that ground corn cobs or shredded paper may increase odor production and shredded paper may increase when used in deep-bedded livestock facilities, whereas wood shavings may have the least impact on air quality and .

Short Communication:Escherichia coliO157 bacteriophages: lytic activity and effects on fermentation in ruminal batch culture

Bach, S. J., Cook, S. R., Wang, Y., Stanford, K., Johnson, R. P. and McAllister, T. A. 2012. Short Communication: Escherichia coli O157 bacteriophages: lytic activity and effects on fermentation in ruminal batch culture. Can. J. Anim. Sci. 92: 545–550. The effect of three lytic Escherichia coli O157, rV5, wV8 and wV11 on in vitro pH, gas production and dry matter disappearance in bovine ruminal cultures were assessed. None of the bacteriophages altered any of the measured parameters in ruminal fluid from concentrate or forage-fed animals. All bacteriophages were able to persist in ruminal fluid from forage and concentrate-fed cattle over a 24-h period; however, lytic activity against E. coli O157:H7 in ruminal batch cultures was not evident.

Survival of Escherichia coli o157:h7 co-cultured with different levels of pseudomonas fluorescens and lactobacillus plantarum on fresh beef

The purpose of this study was to investigate the effect of different levels of Pseudomonas fluorescens (10(2) and 10(6) log10 cfu/ml) and Lactobacillus plantarum (10(2) and 10(4) log10 cfu/ml) on the growth of Escherichia coli O157:H7 on beef loins. Beef loins inoculated with E. coli O157:H7 and P. fluorescens were aerobically stored for 7 days at 4 ºC, while those inoculated with E. coli O157:H7 and L. plantarum were vacuum packaged and stored for 8 weeks at 4 ºC. Aerobic Plate Counts (APC), E. coli O157:H7 and either P. fluorescens or L. plantarum counts were determined at different storage intervals. For the aerobically packaged beef loins, E. coli O157:H7 was detected throughout the 7 day storage period regardless of the P. fluorescens level in the inoculum. For the vacuum packaged beef loins, similar inoculum levels of E. coli O157:H7 and L. plantarum allowed E. coli O157:H7 to survive until week 5 of storage, while a higher inoculum level of L. plantarum inhibited E. coli O157:H7 from week 3. Once fresh beef has been contaminated with E. coli O157:H7, the level of P. fluorescens in the background flora does not inhibit its survival and growth. However, under vacuum storage, the application of L. plantarum as a biopreservative inhibits the survival of E. coli O157:H7 on beef. The higher the level of L. plantarum in the system, the earlier the onset of the inhibition. Farmers and abattoirs have to strengthen preventive strategies to eliminate contamination of beef carcasses with E. coli O157:H7.

Effects of mucin and its carbohydrate constituents on Escherichia coli O157 growth in batch culture fermentations with ruminal or fecal microbial inoculum

In cattle, Escherichia coli O157 generally persists in the large intestine more often than in the rumen. In contrast to the rumen, the large intestine is lined by an epithelial membrane that secretes mucus. We hypothesize that substrates contained in intestinal mucus may constitute a source of energy that is preferentially used by E. coli O157. Therefore, our objective was to test the effects of mucin and its carbohydrate constituents on in vitro growth of E. coli O157 in ruminal or fecal microbial fermentations. Ruminal contents and feces were collected from a ruminally cannulated donor steer fed a corn grain-based finishing diet. Ruminal contents were strained through 2 layers of cheesecloth and incubated at 39 degrees C for 1 h; the floating hay mat was removed with a vacuum suction; and the remaining material was utilized as rumen microbial inoculum. Feces were suspended in physiologic saline to increase fluidity, blended, and strained through 2 layers of cheesecloth. The resulting fluid was utilized as fecal microbial inoculum. Fermentations (50 mL) were performed in serum bottles with a 2:1 mineral buffer to microbial inoculum ratio. Substrates (mucin, fucose, galactose, mannose, gluconic acid, galacturonic acid, glucuronic acid, galactosamine, and glucosamine) were added at 10 mg/mL. A mixture of 5 strains of nalidixic acid-resistant (Nal(R)) E. coli O157 strains was added to each fermentation and concentrations were determined after 0, 6, 12, and 24 h of incubation. In ruminal fermentations, fucose, mannose, glucuronic acid, galacturonic acid, glucosamine, galactosamine, and mucin had no effect on Nal(R) E. coli O157 concentration compared with the control (no substrate added) fermentation. At 24 h of fermentation, the mean concentration of Nal(R) E. coli O157 in fermentations with galactose was less than the control. However, including gluconic acid as substrate increased Nal(R) E. coli O157 concentration at 24 h. In fecal fermentations, mannose, galactose, gluconic acid, glucuronic acid, galacturonic acid, glucosamine, and mucin increased Nal(R) E. coli O157 growth compared with control at 24 h, whereas galactosamine and fucose did not. Gluconic acid was the most stimulatory substrate, increasing Nal(R) E. coli O157 by more than 1.0 log in ruminal fermentations and 2.0 log in fecal fermentations. In summary, availability of mucous constituents, particularly gluconic acid, may explain the greater prevalence of E. coli O157 in the large intestine compared with the rumen of the digestive tract.

Shedding of escherichia coli O157:H7 by cattle fed diets containing monensin or tylosin

Monensin and tylosin have activity against gram-positive bacteria, and it has been theorized that their effects on the intestinal environment may promote proliferation of gram-negative bacteria such as Escherichia coli. Effects of these antibiotics on the shedding of E. coli O157:H7 were studied in a feedlot environment, using 32 finishing steers. A diet containing 85% barley grain, 10% barley silage, and 5% supplement was amended with 33 ppm monensin, 11 ppm tylosin, both of these additives, or no additives (control). All steers were orally inoculated with 10(10) CFU of a mixture of four strains of nalidixic acid-resistant E. coli O157:H7. Fecal (grab), oral (mouth swab) and water, water-water bowl interface, feed, and pen floor fecal pat samples were collected weekly for 12 weeks. Prevalence of E. coli O157:H7-positive fecal grab samples did not differ (P = 0.26) among treatments, nor did the rate (P = 0.81) or duration (P = 0.85) of shedding of the organism. Fecal grab samples were positive for E. coli O157:H7 more frequently (P < 0.001) than were oral swabs. More (P = 0.02) E. coli O157:H7-positive oral swabs were recovered from the tylosin group than from controls. E. coli O157:H7 was not detected in any of 47 water samples, but was present in 1 of 47 water bowl swabs, 7 of 48 feed samples, and 36 of 48 fecal pats. Pulsed-field gel electrophoresis suggested that differences existed among inoculated strains in their ability to persist in animals and in the environment. However, this study revealed no evidence that dietary inclusion of monensin or tylosin, alone or in combination, increased fecal shedding of E. coli O157:H7 or its persistence in the environment.

Shiga toxin-producing Escherichia coli: pre- and postharvest control measures to ensure safety of dairy cattle products

The large number of cases of human illness caused by Shiga toxin-producing Escherichia coli (STEC) worldwide has raised safety concerns for foods of bovine origin. These human illnesses include diarrhea, hemorrhagic colitis, hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura. Severe cases end with chronic renal failure, chronic nervous system deficiencies, and death. Over 100 STEC serotypes, including E. coli O157:H7, are known to cause these illnesses and to be shed in cattle feces. Thus, cattle are considered reservoirs of these foodborne pathogens. Because beef and dairy products were responsible for a large number of STEC outbreaks, efforts have been devoted to developing and implementing control measures that assure safety of foods derived from dairy cattle. These efforts should reduce consumers' safety concerns and support a competitive dairy industry at the production and processing levels. The efficacy of control measures both before harvest (i.e., on-farm management practices) and after harvest (i.e., milk processing and meat packing) for decreasing the risk of STEC contamination of dairy products was evaluated. The preharvest measures included sanitation during milking and management practices designed to decrease STEC prevalence in the dairy herd (i.e., animal factors, manure handling, drinking water, and both feeds and feeding). The postharvest measures included the practices or treatments that could be implemented during processing of milk, beef, or their products to eliminate or minimize STEC contamination.