Avijarna patogena Escherichia coli: virulencija, dijagnostika i prevencija
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Avian colibacillosis is a disease of poultry of all ages. The disease is caused by Avian Pathogenic Escherichia coli (APEC) which often constitute gut flora of healthy chickens together with commensals. If birds are exposed to stress, APEC migrates from the intestine to parenchymatous organs, causing inflammation and mortality. Even if chickens are not exposed to any kind of stress, APEC still has an impact on poultry health all around the world. We conduct diagnostic of APEC, by multiplex PCR system, based on the identification of five virulence genes proposed by T. Johnson et al., 2008. The target genes are as follows: iroN and iutA, genes which are receptors for outer membrane siderophore, a molecule that mediates iron uptake in iron-poor environment, the ompT gene that encodes surface membrane serine protease in Gram negative bacteria which activates plasminogen to plasmin and cleave cationic peptides with antibiotic activity, hlyF gen encodes hemolysin and the increased serum survival gene iss which encodes a protein that mediates resistance to complement in serum. Besides these virulence genes, APEC strains can also possess a bacteriocin gene (Colicin V) which is another important virulence factor. Extraintestinal pathogenic E. coli which causes urinary tract infections in humans belong to phylogenetic group B2, while APEC is affiliated to phylogenetic groups A, B1 and D. However, since extraintestinal pathogenic E. coli from humans and animals share common virulence genes on plasmids, these isolates are considered highly related. Serological typing of the O antigen in APEC has been used in epidemiology investigations and for development of vaccines. Nevertheless, serological typing allows identification of only a limited number of E. coli isolates. Animal welfare, good management practice and vaccination are important strategies in the prevention of APEC. Molecular methods for detection of APEC are important in epidemiology investigation.