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Systems Approach to Effective Control of E coli

13 September 2010

Lactic Acid Bacteria used as a pre- and post-harvest intervention can be a an effective control of E.coli 0157 according to a study caried out by researchers at Texas Tech and West Texas A&M Universities and the Nutrition Physiology Corporation.

The researchers, Mindy M Brashears from Texas Tech, Guy H Loneragan from West Texas A&M and D Ware from the Nutrition Physiology Corporation reported their findings to the ProSafe Advancing Beef Safety through Research and Innovation conferecne in Ireland last year.

In their report, they outlined the virulence of Escherichia coli O157:H7, which they said causes a severe bloody diarrheal illness which can lead to kidney failure or death.

Cattle are the primary reservoir for the pathogen with beef products being commonly associated with outbreaks of the illness.

Lactic acid bacteria (LAB), and specifically Lactobacillus acidophilus NP51, produce inhibitory compounds that can potentially control pathogens in multiple environments if properly managed, the research team said.

The objective of the research was to determine the reduction of E. coli O157:H7 in beef feedlot cattle using NP51 when fed as a direct-fed microbial and in beef products as a direct additive.

They conducted two studies.

In the first study, a meta-analysis was conducted on 13 studies evaluating cultures containing a 1 x 109 dose of the LAB NP51 for the reduction of either shedding of E. coli O157:H7 in the feces and/or the prevalence on the hides.

In the second study, warm and cold beef surfaces and raw ground beef were inoculated with a 1 x 105 dose of E. coli O157:H7 supplemented with a 1 x 109 cfu either per cm2 or per gram and then held at 5°C over a 48 hour period.

Samples were collected at 0, 6, 12, 24 and 48 hours to determine pathogen reductions compared to a control containing no NP51 supplementation.

The E. coli O157:H7 pathogen was recovered on MacConkey’s agar using a thin layer of trypic soy agar to allow for cell recovery.

In the first study, the faecal carriage in the beef was reduced from 26.5 per cent in the animals not exposed to the NP51 to 12.7 per cent in animals fed a diet supplemented with NP51.

The hide carriage in animals not exposed to the NP51 was at 20 per cent while it was significantly lower in the animals exposed to the NP51 at 11.3 per cent.

In teh second study, in all beef products there was a 90 per cent reduction after six hours exposure to the NP51 compared to the controls.

After 24 hours, the reductions were up to 99 per cent in the ground beef with a final reduction of 99.9 per cent observed after 48 hours.

The research team said that there appeared to be no residual effect in the hot and cold surface applications.

Application of Lactic Acid Bacteria to beef products resulted in no adverse sensory parameters, they said.

They concluded that LAB NP51 can be used in both pre and post-harvest environments as a key component within a systems approach to control E. coli O157:H7 and thereby improve the overall safety of the beef supply in a farm to fork approach.

Further Reading

- You can view the full proceedings by clicking here.

July 2010

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