Research Accomplishment Reports 2010

Enteric Diseases of Swine and Cattle: Prevention, Control and Food Safety

M.C. Newman
Department of Animal and Food Sciences

 

Non-Technical Summary

1) Most food-borne illness events are of undefined etiology, stressing the need for identification and characterization of novel, emerging, or previously unrecognized agents, which undoubtedly account for many of these cases.

2) Most of the known bacterial, viral and parasitic food-borne disease agents are primarily zoonotic in nature.

3) Several of these agents are also severe pathogens of animals or have close relatives that are animal pathogens, such that investigation of the host-parasite relationship in animal models or in fact in the animal populations themselves will be informative regarding the host-parasite interactions in humans.

- Focus on emerging or currently unrecognized agents that result in food-borne human illness or enteric diseases of domestic animals, proposing research on the identification, characterization and development of diagnostics for emerging or currently unrecognized agents.

- Development of effective and practical interventions to reduce prevalence of agents already characterized to be of major importance in food safety and / or animal health, based on research on the ecology of the agents and their epidemiology and population dynamics in animal reservoirs.

- Provide training and continuing education to disseminate knowledge regarding new and emerging agents and interventions effective at reducing enteric disease agent incidence and prevalence.

2010 Project Description

Traditionally determination of the nutritional impact of antibiotics in swine diets have largely focused on effects related to the digestibility and utilization of protein and energy. Recent research has demonstrated that antibiotics may increase P digestibility. Because of the importance of P in diet cost and in waste management plans, the present study evaluated the potential impact of two antibiotics - bacitracin methylene disalicylate (bacitracin) and tylosin - on P digestibility and pathogen populations in swine.

Ileal samples were taken immediately after slaughtering each pig to assess the bacterial profile and digesta pH. Samples consisted of about 60 cm section of the distal ileum and its contents. Sampling involved a double ligation with a cotton thread of both ends of the ileal section, removing the ileum portion, and transporting it on ice to the laboratory for pH determination and bacteria culturing. The quantification of phytate-utilizing bacteria populations, as colony-forming units per gram of ileal contents (CFU/g), was conducted according to the procedure described by Bae et al. (1999). Clostridium perfringens, coliform and Escherichia coli populations were monitored to identify the antibiotics effects on these potential pathogens.

2010 Impact

The primary focus is on the impact of this use on the development of antibiotic resistance, which may contribute to a loss of effectiveness of antibiotics in general. More specifically, there is significant concern that a connection may exist between the use of antibiotics in animal agriculture and both the increase of antibiotic resistance transfer to humans and a reduction in the effectiveness of specific antibiotics to treat human diseases.

When evaluating the potential impact of antibiotic use in animal agriculture on human health, it is important to consider a very significant link that connects these elements: the food supply. The development of a reservoir of antibiotic resistance genes in the GIT of food animals contributes to increase.

Bacteria within the GIT that house tetracycline resistance genes can transfer these genes not only to each other but also to transient bacteria. In addition, non-pathogenic bacteria within the intestinal microflora may acquire tetracycline resistance genes from transient resistant bacteria.

These facts emphasize an important point; reservoirs of tetracycline resistance genes in the GIT of animals and humans can participate in genetic transfer because bacteria do not have to be capable of colonization for successful genetic sharing. As a result of this understanding regarding the impact of GIT reservoirs of tetracycline resistance genes, it is important to study the numerically predominant GIT bacteria to understand the true extent of the antibiotic resistance problem and obtain the best estimate of each population as a potential reservoir.

Several studies conducted to evaluate the predominant bacterial populations in pig feces and manure storage pits found that they were primarily composed of anaerobic, low G+C Gram-positive bacteria.

Among the most significant bacterial types in the diverse GIT environment are Lactobacilli, which can be isolated from all regions of the GIT including the stomach, small intestine, and large intestine. Lactobacilli are also of great interest because they are considered beneficial bacteria that contribute to the competitive exclusion of pathogens; for example, they have been found dominating the proximal regions of the immature piglet GIT, which may provide early protection against colonization by pathogens. They are commonly used as probiotics and are a target population for the development of prebiotics to support their continued growth.

It is important to fully elucidate the extent to which this population of bacteria house and maintain resistance traits and genes within the GIT environment of pigs as a potential reservoir of tetracycline resistance genes.

2010 Publications

M.D. Lindemann, A.D. Quant, J.S. Monegue, M. Wang, G.L. Cromwell, and M.C. Newman. 2010. Evaluation of antibiotic effects on phosphorus digestibility and utilization by growing-finishing pigs fed a phosphorus-deficient, corn-soybean meal diet. J. Anim Sci. (first published on January 15, 2010 online as doi:10.2527/jas.2009-2441).