الفهرس 
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Abstract
This study was carried out in Alexandria Province for a period of 12 months from
November 2021 to October 2022 in the laboratory of Department of Animal Hygiene and Zoonoses, Faculty of Veterinary Medicine, Alexandria University for isolation and molecular identification of some food borne zoonotic agents including E. coli, Salmonella and Campylobacter from some food products of animal origin as well as humans. In addition, the antimicrobial susceptibility testing of the identified bacterial strains was assessed.
A total of 450 food samples, comprising chicken paneeh, chicken burger, chicken luncheon, minced meat, beef burger, and kariesh cheese (75 each), were randomly gathered from Alexandria province. In addition, a total of 100 human stool samples have been obtained from 60 diarrheal individuals and 40 apparently healthy ones.
It was recorded that the recovery rate of Coliform bacteria from food products on sorbitol MacConkey agar (SMAC) was 24, 10.7, 13.3, 16, 10.7 and 12 % for Chicken paneeh, Chicken burger, Chicken luncheon, Minced meat, Beef burger and Kariesh cheese, respectively.
On the other side, the biochemical identification revealed that the detection rate of E. coli was 8, 4, 5.3, 5.3, 2.7 and 5.3 % in the same samples, respectively, the detection rate of Citrobacter freundii was 6.7, 4, 4, 4, 2.7 and 4 % in the same samples, respectively and that of Citrobacter braakii was 9.3, 2.7, 4, 6.7, 5.3 and 2.7 % in the same samples, respectively.
Moreover, identification of coliform bacteria by VITEK 2 system clarified that the detection rate of E. coli was 8, 2.7, 5.3, 5.3, 2.7 and 4 % in Chicken paneeh, Chicken burger, Chicken luncheon, Minced meat, Beef burger and Kariesh cheese, respectively while the detection rate of C. freundii was 5.3, 4, 4, 2.7, 1.3 and 4 % in the same samples, respectively and the detection rate of C. braakii was 6.7, 2.7, 4, 4, 5.3 and 2.7 % in the same samples, respectively.
Serotyping of 21 isolates of E. coli revealed the detection of 10 isolates of O157: 7 serotype (EHEC) in the examined food samples of with an incidence of 47.6 %, 5 isolates of O111:H8 serotype (EHEC) in the examined samples of with an incidence of 23.8 %, 4 isolates of O26:H11 serotype (EHEC) in the samples with an incidence of 19.0%, 1 isolate of O125:H21 serotype (ETEC) in the samples with an incidence of 4 .8% and 1 isolate of O128:H2 serotype (EAEC) in the samples with an incidence of 4.8 %.
Molecular detection of some virulence genes in isolates of E. coli (n=21) recovered from food products clarified the presence of Stx1gene in 5 isolates (23.8 %), Stx2 gene in 5 isolates (23.8 %), eaeA gene in 19 isolates (90.5 %) and hlyA gene in 15 isolates (71.4 %).
Antimicrobial susceptibility of E. coli strains (n=21) isolated from food products revealed that Doxycycline was the most effective antibiotic against the tested isolates (90.5%) followed by Nalidixic acid (76.19%) then Tetracycline (57.14%) while Cephalexin and Vancomycin were the least effective antibiotics (19 and 23.8 %, respectively).
Isolation of Salmonella from food samples on XLD clarified that the recovery rate was 12, 8, 5.3, 13.3, 9.3 and 5.3 % for Chicken paneeh, Chicken burger, Chicken luncheon, Minced meat, Beef burger and Kariesh cheese, respectively (40 isolates) while biochemical identification showed that the detection rate was 9.3, 5.3, 5.3, 8, 5.3 and 4% from the same samples, respectively (28 isolates only). Moreover, the molecular identification revealed the detection of 11 isolates only. Finally, the serological identification of 11Salmonella isolates clarified the presence of S. Enteritidis, S. Haifa, S. Inganda, S. Tamale, S. Typhimurium and S. Shangani with various rates.
Antimicrobial susceptibility of Salmonella strains (n=11) isolated from food products revealed that Ciprofloxacin was the most effective antibiotic against the tested isolates (90.9 %) followed by Doxycycline (72.73 %) then Nalidixic acid (63.64 %) while Cephalexin and Erythromycin were the least effective antibiotics as it was noticed that 100% of isolates were resistant.
The detection rate of Campylobacter spp. from foods of animal origin by real time PCR was employed and clarified that C. jejuni was detected with an incidence of 30, 10 and 4.5% in the examined samples of Chicken Kofta, Chicken burger, Chicken luncheon, respectively. On contrary, C. coli cannot be detected in the same samples.
Concerning human stool samples, it was recorded that the recovery rate of coliform bacteria on SMAC was 36.7 and 37.5 % in diarrheic and apparently healthy individuals, respectively. In addition the biochemical identification revealed the presence of E. coli with an incidence of 20 and 10 %, respectively, C. freundii with an incidence of 13.3 and 7.5 %, respectively and C. braakii with an incidence of 13.3 and 5 %, respectively. Moreover, identification by using VITEK 2 system revealed the presence of E. coli with an incidence of 11.7 and 5 %, respectively, C. freundii with an incidence of 18.3 and 10 %, respectively and C. braakii with an incidence of 16.7 and 7.5 % in diarrheic and apparently healthy individuals, respectively.
Serological identification of E. coli isolates (n=9) recovered from stool samples revealed the presence of O127:H40 strain (2 isolates), O115:H38 strain (4 isolates) and O157:H7 strain (1 isolate).
Molecular detection of some virulence genes in isolates of E. coli (n=9) recovered from stool samples clarified the presence of Stx1gene in 1 isolate (11.11 %), Stx2 gene in 1 isolate (11.11 %), eaeA gene in 9 isolates (100 %) and hlyA gene in 7 isolates (77.78 %).
Antimicrobial susceptibility of E. coli strains (n=9) isolated from stool samples revealed that Doxycycline was the most effective antibiotic against the tested isolates (88.9 %) followed by Nalidixic acid (77.8%) then Cefotaxim, Penicillin G and Tetracycline (55.6%) while Cephalexin and Vancomycin were the least effective antibiotics (22.22%).
Isolation of Salmonella from the stool samples on XLD (43 isolates) clarified that the recovery rate was 53.3 and 27.5 % for diarrheic and apparently healthy individuals, respectively while biochemical identification tests showed that the detection rate was 25 and 10 % for diarrheic and apparently healthy individuals, respectively (19 isolates only). In addition, the molecular identification of isolates revealed the detection of 16 isolates only. Finally, the serological identification of Salmonella isolates (n=11) recovered from food products clarified the presence of S. Enteritidis, S. Haifa, S. Inganda, S. Typhimurium, S. Montevideo and S. Tsevie with various rates.
Finally, antimicrobial susceptibility of Salmonella strains (n=11) isolated from food products revealed that Vancomycin and Doxycycline were the most effective antibiotics against the tested isolates (93.75 %) while it was noticed that 100% of isolates were resistant to the remaining antibiotics (Ampicillin, Cefotaxim, Cephalexin, Ciprofloxacin, Erythromycin, Nalidixic acid, Penicillin G, Streptomycin and Tetracycline).