Molecular and Serological Characteristics of Avian Pathogenic Escherichia coli Isolated from Various Clinical Cases of Poultry Colibacillosis in Poland

SIMPLE SUMMARY: Infections caused by avian pathogenic Escherichia coli (APEC) represent a serious threat for poultry production and economic losses. These bacteria have a number of mechanisms that enable them to colonize various ecosystems. We analyzed E. coli from chicken and turkey broilers, laying hens, and broiler parents. In this work, we characterized virulence factors in APEC isolated from poultry in Poland. We also attempted to show a correlation between lesion severity, the presence of virulence genes, and the E. coli serogroup. The most prevalent serotype among E. coli isolates from all types of chickens was serotype O78, in contrast to isolates from turkeys, in which the prevalence of four serotypes, O1, O2, O18, and O78, was similar. Once the serotype was distinguished, it was possible to assign certain virulence characteristics to the isolate and to associate it with the symptoms present, as well as to track the frequency of occurrence. All of the eight virulence genes analyzed were most common in cases with severe, generalized disease processes. The results also confirmed that there is a great variety of APEC strains in the poultry population. ABSTRACT: Escherichia coli infections are a major problem in modern poultry production. Avian pathogenic E. coli (APEC) strains have several mechanisms that enable them to colonize various ecosystems. In this study, 290 E. coli isolates were recovered from clinical cases of colibacillosis in chicken and turkey broilers and from laying and breeding hens. The samples were taken from organs with pathological changes suggesting colibacillosis. The lesions were assigned to three groups depending on their advancement, of which the largest (60% of the isolates) was group 3, with the most extensive changes. The most common serotype was shown to be O78 (14%). The most frequently detected gene among those tested was iss, while papC was the least prevalent. An analysis of the number of genes present per isolate revealed that the presence of four genes was the most common (22%), while only 1% of the strains tested had all eight genes. The most frequently detected genes for each serotype were iss and iucD for O78; irp2 and cvi/cva for O1; irp2, iucD, and iss for O2, and iss and iucD for O8, for which the least frequent was papC. All O18 serotype strains had the iss gene, while none had the vat gene.