الفهرس 
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Abstract
Food contamination with antibiotic-resistant bacteria could be a major threat to public health because the antibiotic resistance can be transferred to other pathogenic bacteria, causing a compromise in the treatment of severe infections. On the other hand the continual application of chemical preservatives caused an accumulation of chemical hazards in the food and feed chain; therefore, a great concern has been paid to herbal plants, as a rich source of natural bioactive elements with health-promoting activities and has no hazardous effect, as an alternative source of antimicrobial substances.
The current study (Use of herbal extract to control foodborne pathogens) aimed at isolation and identification of pathogenic E. coli and coagulase-positive S. aureus from two retail meat products (minced beef and beef burger) marketed in Egypt, as well as to investigate the antimicrobial patterns of the isolates. Furthermore, to evaluate the antimicrobial efficiency of turmeric and marjoram extracts against isolated pathogenic strains. Fifty fresh minced beef samples and 50 frozen beef burger samples were examined for detection of pathogenic E. coli and coagulase-positive S. aureus.
Out of 50 samples, 26% and 36% of the examined minced beef sample were containing coagulase-positive S. aureus and pathogenic E. coli, respectively. The serological identification of E. coli revealed that E. coli O157, O158, O114, O142, O44, O86, O25 represented 5.5%, 33.3%, 33.3%, 5.5%, 5.5%, 5.5% of E. coli isolates, respectively, while one isolate was untyped. On the other hand, 10% of beef burger samples contained coagulase-positive S. aureus, whereas the beef burger did not contain E. coli strains.
Results of antimicrobial susceptibility testing showed that E. coli isolates revealed various degrees of resistance to tetracycline, streptomycin, gentamicin, sulphamethoxazole/trimethoprim, ciprofloxacin, ampicillin amoxicillin/clavulanic acid, , and cefotaxime with the percentage of 94.1, 75.4, 64.7, 41.1, 29.4, 29.4, 17.6, 11.7, respectively. On the other side, they showed a high sensitivity pattern to imipenem, cefoxitin, and nalidixic acid with percentages 100%, 88.2%, and82% respectively.
Coagulase-positive S. aureus isolates showed that they were resistant to rifampin (88.8%), clindamycin (83.3%), erythromycin (72.2%), azithromycin (66.6%), tetracycline (61.1%), and gentamicin (27.7%). About 72.2% of S. aureus samples and 5 serogroups of E. coli were MDR as they resistant to three or more of antibiotic classes.
Four isolates of S. aureus isolated from minced beef and beef burger samples showed the highest MDR ratios were selected for molecular identification for the presence of mecA gene and coa virulent gene, mecA gene and coa virulent gene were detected in the four selected S. aureus isolates.
The antimicrobial resistance pattern and virulence genes of 7 serogroups of pathogenic E. coli were detected for the presence of virulent genes. The eaeA gene was detected in all tested serogroups of pathogenic E. coli, while stx1 was detected in E. coli O157 only.
The investigation of antimicrobial effect of ethanolic extract of marjoram and turmeric against the isolated strains of coagulase-positive S. aureus and E. coli in-vitro by using of well diffusion method, showed that Marjoram extract displayed higher effectiveness than turmeric against S. aureus isolated strains, as the inhibition zone diameters were 2.69, 9.78, 14.63, and 22.06 mm for concentrations 1.25, 2.5, 5, and 10 % of marjoram extract, respectively.
Whereas, in the case of turmeric extract, the inhibition zone diameters accounted for 1.39, 1.9, 3.63, and 19.21 mm for concentrations 1.25, 2.5, 5, and 10 %, respectively . On the other hand, both marjoram and turmeric extracts did not show any antimicrobial effect against MDR E. coli isolates.