Epidemiology of Avian pathogenic Escherichia coli (APEC) in a finisching male turkey farm: longitudinal survey of three consecutive production cycles.

The purpose of this study was to investigate the epidemiology of APEC (Avian Pathogenic Escherichia coli), in a finishing male turkey commercial farm, conducting longitudinal surveys of three consecutive production cycles. The diversity and the distribution of APEC strains during the production cycles were examined using microbiological and molecular techniques. APEC isolates were serotyped, assessed for the presence of virulence-associated genes (pathogenic potential – pathotype) and for resistance to antibiotics (resistotype). Random Amplified Polymorphic DNA (RAPD) was applied to analyse their genetic relationship. Strains of high genetic homology were grouped into the same RAPD cluster (RAPD type). Sampling included, when colisepticemic or articular lesions were observed, viscera and joints from day one until 14 weeks. In the first cycle, APEC O78 was the most prevalent serotype with all isolates sharing the same resistotype and pathotype. Seven of them were included in the same RAPD cluster indicating high genetic similarity. In this cycle, APEC O111 was detected and this represents, to our knowledge, In the second cycle, APEC O2 isolates predominated at the beginning, while O78 strains appeared later until the end of the survey. APEC O2 were classified in two resistotypes, same pathotype and RAPD type. APEC 078 belonged to three resistotypes, same pathotype and three RAPD types. APEC O78 strains, differently from serotype O2, were detected from both colisepticemic viscera (such as brain, pericardium, lungs) and joints. The articular tropism of this serotype is unique as it was observed only in APEC O78 strains of this cycle and of the previous one. Moreover, RAPD molecular studies identified a specific articular O78 cluster, including two strains, which was different from other RAPD clusters including O78 and O2 colisepticemic strains.