Z-010. Genotypic Variation in APEC Isolates from Healthy Turkey Poults across the United States

F. Lago, G. Siragusa, D. Karunakaran, T. Rehberger;
Agtech Products, Inc., Waukesha, WI.

Avian Pathogenic E. coli (APEC) is the causative agent for colibacillosis in turkey poults. The cardinal sign of this major poultry disease is a severe diarrhea that can lead to the death of the infected bird. Effective control of APEC levels in the gastrointestinal tract (GIT) requires a more complete understanding of the genotypic variation of the virulent APEC population in healthy poults. This investigation determined APEC genetic diversity at 5 locations within the United States. Gastrointestinal tracts from 115 healthy poults without colibacillocis clinical signs from 10 to 30 days of age, were collected from houses across the US; 19 from Missouri (MO), 15 From Ohio (OH), 18 from North Carolina (NC), 15 from South Carolina (SC) and 48 from Virginia (VA). GIT mucosal scrapings were plated on ChromAgar for enumeration of Escherichia coli (E. coli), and analyzed for presence of two or more genes associated with virulence (iss, iucC, tsh, cvaC) as a basis for APEC classification. Up to five isolates were collected from each poult, resulting in 110 isolates from MO, 90 from OH, 78 from NC, 72 from SC and 93 from VA. In total 429 isolates were obtained. Multiplex PCR performed on the isolates targeting the four virulence genes associated with colibacillosis, resulted in 28% (121/429) pathogenic isolates, and were distributed at a 15% average across the 5 locations. Iss was present in 63 isolates, iucC in 93 isolates, tsh in 85, and cvaC in 95. Randomly Amplified Polymorphic DNA (RAPD) PCR was used to determine the diversity among the 121 pathogenic isolates. The resulting dendrogram showed that the isolates resolved by geographic region. At 80% correlation, the isolates also clustered into 54 families. Twenty four clusters had 2 or more isolates and 20 clusters had only one isolates. No correlation between pathogenicity gene profile and clustering was observed. This study demonstrated that APEC-derived colibacillosis associated virulence genes are consistently present in healthy poults and that the high level of within-region diversity would indicate that a genotype based strategy to control APEC levels is warranted.