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Evaluation of the Influence of Bacteriophage Titer on the Treatment of Colibacillosis in Broiler Chickens¹

Poultry Production and Product Safety Research Unit, USDA, Agricultural Research Service, Poultry Science Center, University of Arkansas, Fayetteville 72701

² Corresponding author: huff{at}uark.edu

Two studies were conducted to determine the efficacy of bacteriophage SPR02 and DAF6 at varying titers to treat colibacillosis in chickens. In Study 1, the treatments consisted of a control, i.m. injection of bacteriophage SPR02 or DAF6, Escherichia coli airsac challenge, and E. coli challenge followed by treatment at different titers with bacteriophage SPR02 or DAF6. The E. coli-challenged birds were injected with 6 x 10⁴ cfu into the left thoracic airsac at 7 d of age. Immediately after the birds were challenged with E. coli, they were treated by administration of bacteriophage SPR02 or DAF6 by i.m. injection into the left thigh with 4 x 10⁸, 10⁶, 10⁴, or 10² pfu. Study 2 was identical to Study 1, with the exception that the E. coli challenge was increased to 9 x 10⁴ cfu, and the titers of SPR02 and DAF6 were slightly less at 3 x 10⁸, 10⁶, 10⁴, and 10² pfu. Both studies were concluded when the birds were 3 wk of age. Mortality in the birds challenged with E. coli in Studies 1 and 2 was 48 and 47%, respectively. The only consistently effective bacteriophage treatment was the highest titer (10⁸ pfu) of bacteriophage SPR02, which significantly reduced mortality from 48 and 47% in the birds only challenged with E. coli (positive control) to 7% in both studies, which was not significantly different from the unchallenged negative control treatments. These studies indicate that an effective multiplicity of infection for i.m. treatment with SPR02 was 10⁴ in this experimental model of colibacillosis. Bacteriophage administered at sufficient titers can be effective therapeutic agents and provide an alternative to antibiotics in the treatment of bacterial diseases.

Key Words: bacteriophage therapy • Escherichia coli • chicken • colibacillosis

¹ Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.