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

Abstract

We characterized 144 Escherichia coli isolates from severe cellulitis lesions in broiler chickens from South Brazil. Analysis of susceptibility to 15 antimicrobials revealed frequencies of resistance of less than 30% for most antimicrobials except tetracycline (70%) and sulphonamides (60%). The genotyping of 34 virulence-associated genes revealed that all the isolates harbored virulence factors related to adhesion, iron acquisition and serum resistance, which are characteristic of the avian pathogenic E. coli (APEC) pathotype. ColV plasmid-associated genes (cvi/cva, iroN, iss, iucD, sitD, traT, tsh) were especially frequent among the isolates (from 66.6% to 89.6%). According to the Clermont method of ECOR phylogenetic typing, isolates belonged to group D (47.2%), to group A (27.8%), to group B2 (17.4%) and to group B1 (7.6%); the group B2 isolates contained the highest number of virulence-associated genes. Clonal relationship analysis using the ARDRA method revealed a similarity level of 57% or higher among isolates, but no endemic clone. The virulence of the isolates was confirmed in vivo in one-day-old chicks. Most isolates (72.9%) killed all infected chicks within 7 days, and 65 isolates (38.1%) killed most of them within 24 hours. In order to analyze differences in virulence among the APEC isolates, we created a pathogenicity score by combining the times of death with the clinical symptoms noted. By looking for significant associations between the presence of virulence-associated genes and the pathogenicity score, we found that the presence of genes for invasins ibeA and gimB and for group II capsule KpsMTII increased virulence, while the presence of pic decreased virulence. The fact that ibeA, gimB and KpsMTII are characteristic of neonatal meningitis E. coli (NMEC) suggests that genes of NMEC in APEC increase virulence of strains.

Occurrence and Antimicrobial Resistance of Escherichia coli in Oysters and Mussels from Atlantic Canada

“…For instance, certain ExPEC virulence genes, such as cnf1 and sfa, present in isolates in restricted areas in our study, are found mostly in ExPEC isolates from humans (Mellata, 2013). On the other hand, other ExPEC virulence genes, such as tsh, present in isolates in open areas in our study, are found more commonly in isolates from birds (Barbieri et al, 2013), although whether this was derived from poultry or wild birds was beyond the scope of this study. In addition, groups A and D isolates, predominant in restricted and prohibited areas in our study, are found mostly in humans, whereas group B1 isolates, predominant in open areas in our study, are more prevalent in cows, sheep, and goats than in humans (Carlos et al, 2010).…”

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

“…Although the APEC pathotype is not yet completely defined (Dziva and Stevens, 2008), many pathogenicity traits, such as adhesins, serum-resistance factors, iron-acquisition factors, and toxins, are known to be associated with these strains (Barbieri et al, 2013). Additionally, large plasmids, such as ColV plasmids, have been associated with E. coli virulence (Waters and Crosa, 1991) and are thought to be important contributors to the APEC pathotype (Ginns et al, 2000;Johnson et al, 2002Johnson et al, , 2006Rodriguez-Siek et al, 2005b).…”

“…Since there is no single gene or set of genes exclusively associated with APEC (Dziva and Stevens, 2008) that is diagnostic of APEC strains, and immunocompromised birds can be infected with less virulent strains and still manifest the disease, in vivo assays are valuable in establishing if a strain isolated from a diseased bird is really capable of causing disease in a healthy bird (Schouler et al, 2012;Barbieri et al, 2013).…”

“…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

“…Apesar de não completamente elucidado o mecanismo de virulência, está comprovado cientificamente que alguns genes são mais frequentes em APEC e, portanto, podem estar relacionados ao desenvolvimento da celulite aviária. Dentre estes, destacam-se os genes iss e iutA, os quais são responsáveis, respectivamente, pela resistência da bactéria ao sistema complemento e por funcionar como receptor do sideróforo aerobactina (Johnson et al 2008a, Johnson et al 2008b, Barbieri et al 2013.…”