Molecular Characterization and Clonal Relationships Among Escherichia coli Strains Isolated from Broiler Chickens with Colisepticemia

Abstract

This study characterized 52 Escherichia coli isolates from distinct diseased organs of 29 broiler chickens with clinical symptoms of colibacillosis in the Southern Brazilian state of Rio Grande do Sul. Thirty-eight isolates were highly virulent and 14 were virtually avirulent in 1-day-old chicks, yet all isolates harbored virulence factors characteristic of avian pathogenic E. coli (APEC), including those related to adhesion, iron acquisition, and serum resistance. E. coli reference collection phylogenetic typing showed that isolates belonged mostly to group D (39%), followed by group A (29%), group B1 (17%), and group B2 (15%). Phylogenetic analyses using the Amplified Ribosomal DNA Restriction Analysis and pulse-field gel electrophoresis methods were used to discriminate among isolates displaying the same serotype, revealing that five birds were infected with two distinct APEC strains. Among the 52 avian isolates, 2 were members of the pandemic E. coli O25:H4-B2-ST131 clone.

Prevalence of ColV Plasmid-Linked Genes andIn VivoPathogenicity of Avian Strains ofEscherichia coli

“…The PS values of the A litter E. coli isolates ranged from 0 to 5.3: 45 (45%) isolates had a PS = 0, and only 2 (2%) had a PS > 5.0. As expected, the average median PS of A litter isolates (1.1) (this work) was significantly lower than the average median PS of APEC isolates (7.5) (previous work) ( Barbieri et al, 2013Barbieri et al, , 2015. The PSs of the A fecal isolates were not determined.…”

“…The APEC strains (n = 192) included 140 previously characterized cellulitis isolates (Barbieri et al, 2013) and 52 previously characterized isolates obtained from various organs (skin, air sacs, liver, heart, and intestine) of broiler chickens with signs of colisepticemia (Barbieri et al, 2015).…”

“…We had previously determined the PS of the APEC isolates: Of the 192 APEC isolates, 63 (33%) had a median PS = 10; 55 (29%) had a 9.9 > median PS > 7.0; 48 (25%) had a 6.9 > median PS > 5.0; and 26 (13%) had a PS lower than 5, among which 4 had a PS = 0 ( Barbieri et al, 2013Barbieri et al, , 2015. In this work, we performed in vivo assays to assess the pathogenicity of the A litter isolates.…”

“…We also determined the in vivo virulence and phylogenetic group of the A litter isolates, and these data were combined with previously established data on the in vivo virulence of APEC strains (Barbieri et al, 2013(Barbieri et al, , 2015. Our aim was to verify whether the presence of the aforementioned genes correlates with the in vivo virulence of avian E. coli isolates from Brazil.…”

Susceptibilidade de duas linhagens comerciais de frango de corte no desenvolvimento de dermatite necrótica e possível relação dos genes iss e iutA de Escherichia coli com a reprodução experimental da doença

“…O fato de os genes de virulência estarem presentes somente nos isolados originários de celulite está de acordo com o observado por Delicato et al (2003) e Barbieri et al (2015), os quais verificaram que os genes iut A e iss estão dentre os encontrados com maior frequência nos isolados obtidos de colibacilose do que nos isolados provenientes de amostras fecais de aves sadias. Vieira et al (2014) observaram mais de 60% de positividade para o gene iss em amostras de celulite, sendo sua presença considerada um forte marcador de virulência em estirpes patogênicas para aves.…”