الفهرس 
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Abstract
6. Summary
This study was carried out in Behera Province for a period of 12 months from July 2022 to June 2023 for isolation and molecular identification of extended - spectrum β-Lactamase producing (ESBL) Salmonella isolated from human, cattle and poultry. In addition, the antimicrobial susceptibility testing of the identified bacterial strains was assessed.
A total of 125 cloacal swabs were collected by sterile swabs from 25 poultry farms (5 samples / farm) located in Behera province including broilers, layers, breeder chicken and ducks. In addition, a total of 50 fecal samples have been obtained from 50 diarrheal animals with different ages. Finally, 50 human stool samples have been obtained from diarrheal individuals ones whose informed consent. Samples were transferred as soon as possible in icebox to laboratory of Animal Health Research Institute (AHRI) for conventional bacteriological analysis.
It was recorded that the rates of isolation of Salmonella from poultry on XLD medium (50 isolates) were 40, 34, 60 and 50 % from cloacal swabs obtained from flocks of broilers, layers, breeders and ducks, respectively. On the other hand, the rates of identification of Salmonella from poultry flocks after biochemical tests (15 isolates) were 20, 17.6, 66.6 and 60 % in flocks of broilers, layers, breeders and ducks, respectively. Finally, the rates of identification of Salmonella by molecular detection of invA gene in biochemically identified Salmonella isolates (13 isolates) were 100, 100, 50 and 83.3 % in flocks of broilers, layers, breeders and ducks, respectively.
Distribution of antibiogram pattern of Salmonella isolates (n=13) obtained from poultry using Beta-lactam antibiotics revealed that the highest resistance rate was recorded in Ceftazimide (100%), followed by Cephalexin and Cefadroxil (92.31% for each) then Ceftriaxone and Imipeneme (84.62% for each) then Piperacillin and Cefotaxime (76.92 % for each) while the least resistance rate was recorded in using Amoxicillin + Clavulanate (69.23%) (β-lactam inhibitors).
Distribution of antibiogram pattern of Salmonella isolates (n=13) obtained from poultry using non β-lactam antibiotics revealed that the highest resistance rate was recorded in Oxytetracycline (92.31%), followed by Ciprofloxacin (76.92%) then Gentamycin (69.23 %) then Nalidixic acid (53.85 %) then Amikacin and Co-trimoxazole (38.46 % for each) while the least resistance rate was recorded in using Colistin (30.77%).
Results of phenotypic characterization of ESBLs producing Salmonella strains from poultry by Double Disc Synergy Test (DDST) clarified that the percentage of detection of ESBL producing Salmonella strains in 13 Salmonella strains isolated from broilers, layers, breeders and ducks was 23.1, 7.70, 7.70 and 30.8%, respectively with an overall percentage of 69.3% (9 out of 13 isolates).
Results of detection of amplification of ESBLs resistant genes in Salmonella strains obtained from poultry samples clarified that CTX gene was detected in 9 isolates, AmpC gene was detected in 10 isolates and IMP gene was detected in 11 isolates.
Results of serological identification of Salmonella strains (13 isolates) obtained from poultry samples revealed the presence of S. Kentucky (9 isolates) in samples collected from layers, breeders and ducks, S. Anatum (2 isolates) in samples collected from broilers and S. Bloomsbury (2 isolates) in samples collected from broilers.
Concerning cattle samples, it was recorded that the overall rate of isolation of Salmonella from the examined samples of cattle on XLD was 42% where 53.33 % in samples collected from calves (≤ 1 year) and 25 % in samples collected from adult animals (> 1 year) while the rate of isolation of Salmonella from cattle after biochemical testing of the recovered isolates was 14.3%. On contrary, the recovered isolates were found to be negative for presence of invA gene by PCR.
Concerning human samples, it was recorded that the overall rate of isolation of Salmonella from stool samples obtained from diarrheic human in relation to age groups on XLD was 54% (27 isolates) where isolation rate in samples obtained from children under 15 years (72%) was higher than that recorded in samples collected from adult individuals (36%). On performing biochemical testing on the recovered isolates, the isolation rate was decreased to 14.81% (4 isolates) where isolation rate in samples obtained from children under 15 years (16.67%) was higher than that recorded in samples collected from adult individuals (11.11%). Finally, invA gene was detected in 3 isolates only so the overall occurrence of Salmonella in human samples was 6%.
Distribution of antibiogram pattern of Salmonella isolates (n=3) obtained from human using βlactam antibiotics revealed that the highest resistance rate was recorded in Ceftazimide and Piperacillin (100%), followed by Ticarcillin, Amoxicillin + Clavulanate, Piperacillin/Tazobactam, Ticarcillin/clavulinic acid and Cefotaxime (66.67%) while the least resistance rate was recorded in using Cefepime, Aztreonam, Imipenem, Meropenem and Cefoxitin.
Distribution of antibiogram pattern of Salmonella isolates (n=3) obtained from human using non β-lactam antibiotics revealed that the highest resistance rate was recorded in Gentamycin and Tobramycin (100%) followed by Amikacin and Co-trimoxazole (66.67%) while the least resistance rate was recorded in using Ciprofloxacin, Pefloxacin, Minocycline and Colistin (33.33%).
Results of phenotypic characterization of ESBLs producing Salmonella strains from human by Double Disc Synergy Test (DDST) clarified that the percentage of detection of ESBL producing Salmonella strains in 3 Salmonella strains 67.7% (2 out of 3 isolates).
Results of detection of amplification of ESBLs resistant genes in Salmonella strains obtained from human samples clarified that CTX, AmpC and IMP gene was detected in 2 isolates while they could not be detected in the remained isolate.
Finally, results of serological identification of Salmonella strains (3 isolates) obtained from human samples revealed the presence of S. Kentucky (2 isolates) in samples collected from children and adults and S. Bloomsbury (1 isolate) in samples collected from children.