Molecular identification, genotyping of virulence-associated genes, and pathogenicity of cellulitis-derived Escherichia coli

Abstract

Background and Aim: Avian colibacillosis, which is caused by avian pathogenic Escherichia coli (APEC), is a major bacterial disease that affects birds of all ages worldwide, causing significant economic losses. APEC manifests in several clinical forms, including cellulitis, and its high pathogenicity is attributed to harboring numerous virulence-associated genes (VGs). This study evaluated the pathogenicity of the cellulitis-derived E. coli (O78) strain through molecular identification of genes coding for seven virulence factors and by conducting an in vivo assessment of capability for cellulitis induction in broiler chickens. Materials and Methods: This study was performed using a previously isolated and identified cellulitis-derived E. coli (O78), which was screened for seven VGs using molecular detection and identification through polymerase chain reaction followed by nucleotide sequencing and phylogenetic analysis. Experimental infection by subcutaneous (SC) inoculation in broilers and its pathogenicity was confirmed in vivo by cellulitis induction. The impact of cellulitis on broiler performance was assessed. Results: Molecular genotyping proved that the isolate harbored five virulence genes (iroN, iutA, tsh, iss, and papC) and was negative for stx1 and hly genes. The amplified products for iroN, iss, and iutA were subjected to sequencing and phylogenetic analysis, and the results indicate the highest similarity and matching with E. coli submitted to the National Center for Biotechnology Information GenBank. SC inoculation of bacteria in broiler chickens resulted in cellulitis, as indicated by thick red edematous skin with yellowish-white material in the SC tissue at the inoculation site, and the abdominal muscle showed redness and increased vacuolization. Histopathological examination revealed moderate-to-severe caseous inflammatory reaction with a marked accumulation of heterophils and mononuclear cells in the SC fatty tissue. The average feed intake, body weight gain (BWG), and feed conversion ratio (FCR) were lower in infected chickens in comparison with those of the control non-infected chickens. Conclusion: This study proves that molecular techniques are accurate for pathogenicity determination in virulent bacteria, with the advantages of being rapid, time-saving, and economical. Cellulitis is associated with economic losses that are represented by a lower BWG and FCR.

Distribution pattern of antibiotic resistance genes in Escherichia coli isolated from colibacillosis cases in broiler farms of Egypt

“…The disease is associated with septicemia, pericarditis, airsacculitis, perihepatitis, peritonitis, and other extraintestinal lesions in poultry and with high economic loss due to the high mortality and low productivity of poultry farms. Many studies have reported an intensive increase in multidrug resistance (MDR) in E. coli strains [1][2][3][4].…”

Virulence and antimicrobial resistance of Escherichia coli isolated from chicken meat, beef, and raw milk

“…The ExPEC have been associated with both human and animal diseases (Manges & Johnson, 2012). It has been reported that foods of animal origin, such as the samples analysed here, are important vehicles for these bacteria and could be implicated in infections of humans and dairy animals (Joanne et al, 2011;Amer et al, 2020). It is important to note that the prevalence of ExPEC recorded in this study was much higher than that recorded in Spain by Quinto and Cepeda (1997) (0.4%) and in Ontario (Canada) by Steele et al (1997) (0.87%).…”

Study of the diversity of 16S–23S rDNA internal transcribed spacer (ITS) typing of Escherichia coli strains isolated from various biotopes in Tunisia

“…Traditional typing systems based on phenotypes (such as serotypes, biotypes, phage types or antibacterial profiles) have been used for many years (Fratamico et al 2016). However, more advanced molecular methods have recently been developed to examine the affiliation of microbial isolates (Amer et al 2020), and these methods have changed our ability to accurately distinguish bacterial types and subtypes (Sabat et al 2013). Since the last decade, several molecular techniques for microbial characterization have been developed.…”