|GADDE, UJVAKA - US Department Of Agriculture (USDA)|
|OH, SUNGTAEK - US Department Of Agriculture (USDA)|
|RITTER, DON - Maintaire Farms|
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2017
Publication Date: 2/4/2017
Citation: Li, C.Z., Lillehoj, H.S., Gadde, U.D., Oh, S., Ritter, D. 2017. Characterization of Clostridium perfringens strains isolated from clinically healthy and necrotic enteritis-afflicted broiler chickens. Avian Diseases. 61:179-186.
Interpretive Summary: Poultry food industry is facing challenges from the increasing costs due to control of infectious diseases with necrotic enteritis (NE) being one of top diseases. NE is caused by an intestinal bacteria called Clostridium perfringens (CP) which produces several toxins that damage the gut and cause poor growth performance. CP also impacts animal welfare and human food safety with estimated economic loss of $6 billion annually in USA. Although NE is currently controlled by using growth promoting antibiotics as feed supplement, increasing pressure about the potential hazard effect of antibiotic resistant bacteria on humans is forcing the poultry industry to withdraw antibiotics from feed. Before an effective alternative solution to reduce antibiotics can be developed, the disease-causing mechanism needs to be elucidated. ARS scientists collected CP strains from healthy and NE-infected birds from poultry farms to analyze bacterial growth patterns, the effect of iron on the bacterial growth, and their ability to reproduce NE disease in chickens. The results showed that certain CP types produce harmful toxins that cause major damage in the intestine. This finding will lead to the development of effective vaccines to control field NE infection.
Technical Abstract: Clostridium perfringens (CP) Type A strains are the main etiological factor for necrotic enteritis (NE), one of the important enteric diseases in poultry, which has gained worldwide attention during the last decade and is responsible for the annual loss of 6 billion dollars in US poultry industry. The increasing occurrence of NE is also found to be associated with the withdrawal of antibiotic growth promoters from the feed in poultry production. There is a general conception that the CP isolates from clinically healthy chickens would not be virulent to induce NE disease. In this report, some C. perfringens strains isolated from healthy and NE-infected birds were characterized microbiologically, molecularly and tested for their virulence in chickens experimentally. All the strains were hemolytic, lecithinase positive, and identified to be CP by the identification kit. The morphology studies showed three different growth shape patterns in these strains when cultured in Brain Heart Infusion (BHI) broth / 0.3% agarose containing FeSO4 and ZnCl2. The CP strains responded differently to treatment by iron chelator 2,2'-bidypinol. The PCR results indicated that these bacteria were all alpha toxin-positive, but seven strains were beta2 toxin-positive (N11, N10, CP1, CP5, CP13, JGS, and Del1), with only strain Del1 being netB-positive. The in vivo studies indicated that most isolates were virulent to reproduce NE diseases in the Eimeria / CP dual infection model, including one CP isolate (strain N11) from the healthy chicken gut. The CP strains of Del1 and N11 merit further investigation to determine the virulence factors and immune protective antigens.