Molecular Analysis of Escherichia coli Strains Causing Respiratory Troubles in Chickens in Egypt

Abstract

Colibacillosis is a complicated disease causing severe economic losses and challenging veterinarians and producers. Therefore, this study aimed to characterize avian pathogenic Escherichia coli (APEC) strains causing respiratory signs in chickens. Thirty broiler chicken flocks at age of 17-35 days showed respiratory signs and greenish diarrhea during 2013-2016 outbreaks that occurred in Sharkia, Ismailia, Dakahlia and Sinai Governorates. The postmortem findings revealed typical colisepticemia picture including air sacculitis, fibrinous pericarditis and perihepatitis. The percentage of APEC isolation was 100%. Mixed bacterial infections with Enterobacter aerogenes or Providencia rettgeri (3 flocks, each), Klebsiella pneumoniae (2 flocks), Serratia liquefaciens or Enterobacter agglomerans (1 flock, each) was evidenced. From 284 collected samples (air sacs, heart blood, lungs and liver), E. coli was predominantly isolated from air sacs (76.1 %) and lung (73.2 %) followed by heart blood (67.6%) and liver (54.9%). Based on serogrouping, the most common serogroups were O78 and O2 with percentages of 15%, each. Utilizing antimicrobial disc diffusion test, the isolates showed 32.7% resistance to doxycycline and 100% resistance to lincomycin, spiramycin, oxacillin and amoxicillin. Polymerase chain reaction (PCR) analysis for 55 MDR E. coli isolates from air sac and heart blood revealed 3 β-lactamase resistance genes; blaTEM (87.3 %), blaCTX-M (85.5 %) and blaOXA (5.5 %) and 6 virulence genes in two multiplex PCR; iucD (96.4%), Fim H (92.7%), iss (76.4%), ompT (58.2%), tsh (45.5%) and cvaC (9.1%). An association of virulence with multidrug resistance genes in E. coli was recorded, that hindered the control measures. Therefore, alternative strategies were necessary to minimize the antibiotic use and reduce the virulent strains' occurrence.

Multiplex PCR for ompT and iss genes of Escherichia coli isolated from chronic respiratory disease (CRD) broiler farms

“…Although the primary function was unclear Rodriguez-Siek et al, 2005;Hassan et al, 2020), they related to increased survival of bacteria and overcame the innate host serum immunity (Sedeek et al, 2020). The results observed no detection of both ompT and iss genes in E. coli isolated from collected samples and this is similar to the results obtained by Ibrahim et al (2019a), which recorded a similar percentage of E. coli isolating from the lung by PCR. The existing study's percentage disagreed with the percentages of 80.4% and 85.9% for ompT and iss genes, respectively reported by Mohamed et al (2018) and with 100% and 91% for both genes reported by Solà-Ginés et al (2015) and Subedi et al (2018) in APEC, respectively.…”

“…The results showed 42% of the isolates from the lung and trachea by the conventional method. This percentage was more than the 31.7% recorded by Abd El-Aziz et al (2022) and less than 75.5%, 73.2% and isolated from broiler lung in other studies (Ibrahim et al, 2019a;2019b;Hassan et al, 2020).…”

“…In contrast, the lower percentage of 2.2% of the ompT gene was also reported by many researchers, such as Mbanga and Nyararai (2015). These differences in gene percentages may resulted from that both ompT and iss genes located with other virulence genes on ColV large virulence plasmid found in the APEC strain (De Oliveira et al, 2015;Mohamed et al, 2018;Ibrahim et al, 2019a), so if these plasmids were absent in E. coli isolate both genes cannot be detected. Furthermore, these plasmids were more frequently located in APEC rather than avian fecal E. coli (AFEC) (Mohamed et al, 2018).…”