Subpatótipos de Escherichia coli patogênica para aves (APEC) podem estar associados às síndromes infecciosas infecciosas causadas no hospedeiro / Subpathotypes of avian pathogenic Escherichia coli (APEC) exist as definid by their syndromes of isolation and virulence traits

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

08/10/2010

RESUMO

Avian Pathogenic Escherichia coli (APEC) cause different types of systemic extraintestinal infections in poultry, which are collectively termed colibacillosis, imposing significant economic casses for the avian industry Among these diseases are septicaemia, omphalitis, cellulites and swollen head syndrome. However, to the date, there is no description of genes or characteristics which allow us to classify avian strains in pathotypes responsible for causing specific diseases in their hosts, as there are for human pathogenic E. co/i strains. In this study we aimed to characterize avian pathogenic E. co/i strains representing 4 groups, one of commensal strains (AFEC - Avian Fecal Escherichia co/i) and 3 groups of pathogenic strains responsible for causing 3 different syndromes in their hosts (septicaemia, omphalitis and swollen head syndrome). The biological characteristics studied were: adhesion to eukaryotic cells, biofilm formation, capacity of synthesizing quorum sensing s1gnaling molecule, presence of pathogenicity island, pathogenicity levels according to lethal dose (50%) assay, phylogenetic group and presence of virulence genes. The comparison between strains based on these genotypic and phenotypic traits, by different multivariate statistics tools and complex network, allowed us to infer. the population structure of the studied group. The results indicate that APEC do not constitute a unique homogeneous group, but a structured set of different subgroups, each one associated to a specific infectious syndrome inflicted to the host, possibly defining pathotypes or subpathotypes within APEC strains. Thus, we suggest the existence of a subpathotype associated to omphalitis, with lethality characteristics similar to AFEC strains, but with a different adhesion pattem, which may be due to a specialization related to the colonization of a particular niche, the egg s yolk sac. Anda subpathotype associated to the swollen head syndrome, equally adapted to pathogenicity, but with more "aggressive" characteristics demonstrated by the high lethality and adhesion levels. Septicaemic strains, however, do not constitute a cohesive group, which suggests a constellation of strains associated to different subpathotypes and capable of, eventually, cause a systemic syndrome (sepsis), due to the clinical evolution of the illness ami/or host immunological conditions. This work is pioneer in demonstrating the existence of subpathotypes within APEC strains, relating different infectious syndromes to specific groups of strains possessing particular genotypic and phenotypic characteristics. These results offer new possibilities in studying the genes responsible for different pathogenesis processes within APEC and for the vaccine developing. It may be important to consider these subgroups in the process of vaccine developing, in the efforts for obtain cross protection, which had not yet being accomplished successfully concerning APEC strains.

ASSUNTO(S)

escherichia coli patogenica aviaria escherichia coli patogenicidade colibacilose escherichia coli pathogenicity avian pathogenic escherichia coli colibacillosis

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