الفهرس 
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Abstract
A total of 240 samples were collected from clinically diseased chicks from private farms in Fayoum, Beni-suef, Giza and All over western Assut Road and examined for the presence of Salmonella microorganisms. A total of 50 bacterial isolates were recovered. The identification of such isolates revealed that they belonged to Salmonella serovars with an incidence of 20.8%. Isolates of Salmonella serovars were recovered from examined samples and serologically typed as Salmonella Kentucky, Salmonella Infantis, Salmonella Hiedelberg Salmonella Labadi. Salmonella Enteritidis Salmonella Typhi Salmonella Agona Salmonella Pullorum Salmonella Newport and Salmonella Virginia. There were two pansusceptible Salmonella isolates (i.e. susceptible to all antimicrobial drugs under test). There was one Salmonella isolate susceptible to one antimicrobial drug under test. The 3 Salmonella isolates were susceptible to 2 antimicrobial drugs under test .A large percentage of isolates were resistant to all Ampicillin (90%), Nalidexic acid (88%),Sulphamethoxasole + Trimethoprim (82%) and Tetracyclines (82%). Approximately 86% of the isolates demonstrated multiple-resistance (i.e. resistance to P3 antimicrobial types), of which 18.75% and 25% were resistant to three and four antimicrobial types, respectively. Resistance to 1/2 antimicrobial types was seen in 2.9% of the isolates. Only one isolate was resistant to 13/14 antimicrobials, one isolate was resistant to 12/14 antimicrobials and 4 isolates were resistant to 11/14 antimicrobials. Phenotypic detection of ESβLs by using screening test (Cefinase®) and confirmatory test by using combined disk diffusion test revealed that 32% of isolates were positive for both tests with 20% similarity and 12% diversity between the two tests. Molecular characterization of some ESβLs genes (blaTEM,blaCTX blaOXA, blaCMY and blaSHV)was done using PCR. The results showed that all the phenotypic positive samples were positive for amplification of one or more genes and noticed that all the isolates were negative for blaCMY gene. Molecular characterization of some virulence genes (invA ,avrA ,sopB ,bcfC ,stn( was done using PCR. The results showed that all the ESβLs positive samples were positive for amplification of all tested virulence genes and noticed that all the isolates were negative for blaCMY gene.