Aim:The aim of this study was to determine the relationship between phenotypic resistance and genotypic resistance of isolated serotyped pathogenic Escherichia coli isolates from the clinically diseased broiler.Materials and Methods:A total of 160 samples (heart, liver, kidney, and lung) were collected from 18 to 34 days old clinically diseased broiler from 40 broiler farms (3-5 birds/farm) reared in Giza and Kaluobaia Governorates for the isolation of pathogenic E. coli. Various E. coli isolates were tested for the pathogenicity based on Congo red (CR) dye binding assay. The obtained CR-positive E. coli isolates were subjected to serological identification using slide agglutination test. Disc diffusion test was used to study the sensitivity pattern of E. coli isolates to available 12 antibiotics. Polymerase chain reaction was performed for the detection of antimicrobial resistance genes in the studied pathogenic E. coli isolates.Results:The results revealed that 56 samples (35 %) were positive for E. coli. The results of the CR assay indicates that 20 isolates of 56 (35.7%) were positive and 36 isolates (64.3%) were negative. Identified E. coli serotypes of CR-positive isolates were 1 (O24), 2 (O44), 2 (O55), 5 (O78), 2 (O86), 1 (124), 3 (O127), 1 (O158), and 3 untyped. Resistance rate in disc diffusion test was 85% to oxytetracycline and kanamycin; 80% to ampicillin (AMP), clindamycin, and streptomycin (S); 75% to enrofloxacin; 65% to chloramphenicol; 55% to cefotaxime and gentamicin (CN); 45% to trimethoprim+sulfamethoxazole; 35% to erythromycin (ERI); and 30% to oxacillin. All strains are multidrug-resistant (MDR). Antibacterial resistance genes CITM, ere, aac (3)-(IV), tet(A), tet(B), dfr(A1), and aad(A1) were detected in 14 (70%), 12 (60%), 12 (60%), 8 (40%), 11 (55%), 8 (40%), and 9 (45%) of tested 20 isolates, respectively. Multidrug resistance was detected in the form of resistance to 42%-83.3% of tested 12 antibiotics. Three isolates (15%) of 20 tested isolates showed a relationship between phenotype and genotype and 17 (85%) showed irregular relation. Strains are sensitive and show resistant gene (P-G+) presented in three isolates for AMP (beta-lactam), one for ERI (Macrolide), as well as five isolates for trimethoprim (pyrimidine inhibitor). E. coli isolates had resistance and lacked gene (P+ G-) reported meanly in one isolate for CN (aminoglycoside), two isolates for tetracycline, four isolates for ERI, seven isolates for trimethoprim, and eight isolates for S (aminoglycoside).Conclusion:The study demonstrates that E. coli is still a major pathogen responsible for disease conditions in broiler. E. coli isolates are pathogenic and MDR. Responsible gene was detected for six antibiotics in most of the isolates, but some do not show gene expression, this may be due to few numbers of resistance genes tested or other resistance factors not included in this study.

Aim: Arthritis is one of the most economic problems facing poultry industry worldwide. The study was done to detect possible causes of arthritis in breeder chicken flock with emphasis on molecular identification of Mycoplasma synoviae (MS). Materials and Methods: This study was carried on chicken from broiler breeder flock of 57 weeks' age in Dakahlia, Egypt, suffered from arthritis with frequently 5-7% decrease in egg production, reduced fertility, and hatchability. Forty blood samples were randomly collected from individual birds in sterile tubes and used for serum separation. Serum samples were tested using serum plate agglutination (SPA) test against colored antigens for Mycoplasma gallisepticum (MG), MS, and Salmonella gallinarum-pullorum (SGP). On the other hand, 24 joint samples were collected. Of those 24 samples, 12 joint samples were subjected to bacteriological examination, while the other 12 were utilized for molecular diagnosis by polymerase chain reaction (PCR) for MS and avian reovirus (ARV). Results: SPA test results revealed the presence of antibodies against MG, MS, and SGP in tested sera in rates of 14/40 (35%), 35/40 (87.5%), and 9/40 (22.5%), respectively. Furthermore, 19 bacterial isolates were recognized from joint samples and identified as five Staphylococcus spp., nine Escherichia coli, three SGP, one Citrobacter, and one Proteus. The identified Staphylococcal isolates were three coagulase-positive staphylococci (two Staphylococcus aureus and one Staphylococcus hyicus) and two coagulase-negative staphylococci (one Staphylococcus epidermidis and one Staphylococcus lentus), while E. coli isolate serotypes were 1 O11, 2 O55, 3 O78, 1 O124, 1 O125, and 1 untyped. PCR proved that 12/12 (100%) samples were positive for MS variable lipoprotein hemagglutinin A (vlhA) gene, while ARV was not diagnosed in any of the examined samples. Four amplified vlhA gene of MS isolates (named MS-2018D1, MS-2018D2, MS-2018D3, and MS-2018D4) was successfully sequenced. Analysis of phylogenetic tree revealed the presence of 100% identity between each two sequenced isolates (isolates MS-2018D1 and MS-2018D4 and also isolates 2018D2 and MS-2018D3). However, the nucleotide similarity between four isolates was 88.6%. On the other hand, our field isolates MS-2018D1, MS-2018D4, MS-2018D2, and MS-2018D3 showed nucleotide identity with vaccine strain MS-H 98.4%, 98.4%, 88.1%, and 88.1%, respectively. Furthermore, the nucleotide similarities with field strains from Argentina ranged between 87.8% and 98.6%. Conclusion: Four field isolates of MS were identified in examined broiler breeder flock. A phylogenetic study of these isolates revealed the variation between isolated MS strains and vaccine strain. Therefore, further studies are required for evaluating the vaccine efficacy against the present field isolates of MS. In addition, application of MS immunization of breeder flocks is necessary for proper control of the disease.

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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.

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