Virulence Factors and Clonal Relationships among Escherichia coli Strains Isolated from Broiler Chickens with Cellulitis

Abstract

In this study, we compared Escherichia coli isolates from chickens with avian cellulitis with those from feces of healthy chickens. Cellulitis-derived strains presented phenotypic and genotypic characteristics of greater virulence than did the fecal isolates. Phylogenetic analysis by repetitive extragenic palindromic-PCR showed that, in agreement with their virulence characteristics, the cellulitis isolates form two clonal groups distinct from the fecal isolates.Escherichia coli causes a variety of diseases in poultry, including respiratory tract infection, omphalitis, swollen-head syndrome, enteritis, septicemia, and cellulitis (3, 7), and these diseases are responsible for major economic losses in the chicken industry. Cellulitis lesions cause carcass downgrading and condemnation losses estimated at $40 million annually (7) in the United States. In Brazil, cellulitis is responsible for 45.2% of the broiler carcasses condemned for skin lesions (2), and the economic losses are estimated at $10 million annually.Some clones of E. coli may be more effective in causing cellulitis, since experimental inoculation of isolates from cellulitis lesions reproduced this disease with a significantly greater frequency (100%) than did inoculation of isolates from airsacculitis lesions (42%) or inoculation of fecal isolates (8%) (9). However, E. coli strains isolated from cellulitis lesions expressed many virulence-associated factors similar to those presented by strains isolated from other colibacillosis lesions and from feces (6, 8), which shows that the expression of these virulence factors by themselves cannot explain the differences in pathogenicity presented by these isolates.Since avian colibacillosis in its different forms occurs worldwide, we can gain a better understanding of its pathogenesis by a phylogenetic analysis of the clonal relations among E. coli isolates in several regions and in different countries. In this study, we used phenotypic and genotypic methods to examine the presence of virulence factors in E. coli isolates obtained in Southern Brazil from broiler chickens and determined by repetitive extragenic palindromic (REP)-PCR the genetic relationship among these isolates and avian fecal isolates.Fifty-two broiler chickens presenting cellulitis were collected from 52 different flocks in Southern Brazil, and from each animal one E. coli strain was isolated from pure culture and maintained by standard procedures. Twelve E. coli strains were obtained from the feces of healthy chickens. Isolates were grown on brain heart infusion agar (Difco) for 18 h at 37°C for phenotypic or genotypic analysis.The following phenotypic properties of the E. coli isolates were evaluated by standard methods (1, 9, 11): antibiotic resistance, pathogenicity to 1-day-old chickens, motility, ability to experimentally reproduce cellulitis (applied to 20 isolates), production of hemolysins, presence of K1 capsule, hemagglutination, production of aerobactin, resistance to chicken serum, and production of cytotoxins to Vero cells. All ...

Virulence factors of avian pathogenic Escherichia coli (APEC)

“…A clonal diversity study with commensal avian E. coil strains and APEC strains performed by Silveira et al (2002b), using ERIC-PCR, demonstrated a relationship between the pathogenicity and the clonal origin of APEC strains. These observations were also made by Brito et al (2003) in APEC strains isolated from chickens with cellulitis. White et al (1993), using multilocus enzyme electrophoresis (MLEE), observed that APEC strains causing septicemia in turkeys belonged to a mixture of specialized pathogenic clones and non-pathogenic opportunist clones.…”

Genotypes and Pathogenicity of Cellulitis Isolates Reveal Traits That Modulate APEC Virulence

“…Cellulitis is one of the most prevalent extraintestinal infections caused by APEC in broiler chickens, and is characterized by the presence of subcutaneous fibrinonecrotic plaques and inflammation of the overlying chicken skin, resulting in rejection of part or all of the carcasses at processing [2], [3], [4], [5]. In Brazil, cellulitis lesions are estimated to cause the loss of 0.14 to 1.4% of poultry meat production [6], leading to losses of at least 18 thousand tons of meat in 2011 [7].…”

Celulite em codornas japonesas alimentadas com extrato de orégano nas dietas e inoculadas com Escherichia coli

“…As aves, cujos tratamentos sofreram desafio, foram inoculadas no 5º e 45º dia do período experimental, com cepas de E. coli, isoladas pela primeira vez por Brito et al (2003). Foi inoculada em cada ave, individualmente com agulha e seringa de insulina estéreis, pela via subcutânea, na região torácica esquerda, 0,1mL de E. coli na concentração de 10 8 UFC/mL.…”