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Pathophysiology of Clostridial  Enteritis and the Impact of Treatment: Lessons from a Chick  Model

H.R. Gaskins1 and Jan Dirk van der Klis2

Departments of Animal Sciences and Veterinary Pathobiology, &

Division of Nutritional Sciences, University of Illinois at Urbana-Champaign1

ID Lelystad B.V., Institute of Animal Science and Health, The Netherlands2

Introduction

Clostridial or necrotic enteritis (NE), caused by Clostridium perfringens type A, suppresses chick growth and is a source of mortality in the  broiler industry. Risk factors for the onset of clinical disease include the removal of antibiotic growth promoters, as well as concurrent coccidia infection and the inclusion of diet components high in nonstarch polysaccharides, both of which stimulate microbial growth through the enhancement of intestinal mucus production. Although toxin production by C. perfringens has been well studied, less is known about its growth characteristics and colonization potential relative to the commensal microbiota in broiler chicks. We report a study with a clostridial enteritis infection model, which used both molecular (16S rDNA)-based and cultivation techniques to determine the effects of a feed grade antibiotic and diet on the structure and mucolytic activity of the small intestinal microbiota relative to colonization with C. perfringens. Birds received a wheat/barley (WB) diet, or a WB diet supplemented with 2% highly methylated citrus pectin (WBP). Both diets were fed with and without 100 ppm Tylan. Experimental diets were fed until 28 days of age. At 20 days of age a crossover design was used, in which birds from the medicated

WBP diet were switched to an unmedicated WBP diet and vice versa. In total, six treatments were included, following the experimental schedule below.

At 10 days of age, the birds were infected with Eimeria acervulina, followed by a C. perfringens inoculation on three consecutive days (days 14, 15, and 16). NE lesions were scored on days 15, 16, 17, and 20. Birds were killed on days 17, 20, and 24 for the collection of digesta and mucosa samples from the jejunum and ileum for microbiological analyses, including a) bacterial population profiles and community structure by 16S rDNA PCR-DGGE (denaturant gradient gel electrophoresis) and cluster analysis; b) mucolytic activities of mucosal bacterial populations by cultivation-based techniques; and c) analysis of C. perfringens colonization by real-time quantitative PCR (Q-PCR).

Results

Microbial community profiles in the jejunum and ileum clusted according to the presence or absence of Tylan on days 17 and 20. By day 24,  four distinct microbial community profiles were observed according to treatments 1-4. A comparison of diet effects independent of antibiotic treatment indicated that jejunal and ileal 16S rDNA banding patterns were more homogeneous in WBP-fed vs. WB-fed birds on days 17 (P < 0.05) and 20 (P < 0.05), but not different on day 24. A comparison of antibiotic effects independent of diet revealed that jejunal and ileal 16S rDNA banding patterns were more homogeneous in Tylan-treated birds than in non-antibiotic-treated birds on days 17 (P < 0.01), 20 (P < 0.01), and 24 (P < 0.05). Tylan reduced (P < 0.05) the number of 16S rDNA bands in jejunal and ileal contents on days 20 and 24 for WB-fed birds and on day 24 for WBP-fed birds.

Tylan reduced (P < 0.01) the percentage of mucolytic bacteria in jejunal and ileal mucosa on days 17 and 20 in WB-fed birds and on day 24 for WBP-fed birds. Tylan reduced (P < 0.01) C. perfringens colonization of the jejunum and ileum on days 17 and 20 for both WB- and WBP-fed birds. Clostridium perfringens was not detectable by Q-PCR on day 24, independent of diet treatment. The disappearance of C. perfringens in Tylan-treated birds on days 17, 20, and 24 correlated with the appearance of a Lactobacillus species, tentatively identified as Lactobacillus gasseri by 16S rDNA-V3 sequence analysis. The inverse relationship between these two bacteria according to Tylan treatment was observed in all birds tested.

Summary and Conclusion

Performance and pathophysiological data demonstrate that, independent of diet, Tylan reduced NE lesions and prevented a corresponding  compromise in barrier function, resulting in a significant improvement in body weight gain. In addition, Tylan reduced both C. perfringens concentrations and the percentage of mucolytic bacteria. Most importantly, the reduction in mucolytic bacteria, in general, and C. perfringens, in particular, correlated in a temporal fashion with improvements in intestinal integrity and barrier function in response to Tylan.

Pathophysiology of Clostridial July 9-11, 2002 The Elanco Global Enteritis Symposium

Enteritis and the Impact of Treatment: Lessons from a Chick Model, “Abstract”, J-3 to J-5