Abstract
Forty nine isolates were isolated from 34 food samples using Salmonella-Shigella medium, 10 of them were identified biochemically as Salmonella sp., two of them were multidrug-resistant, and they showed a resistance to seven tested antibiotics (ampicillin, streptomycin, gentamicin, nalidixic acid, ciprofloxacin, tetracycline, amoxicillin). Molecular identification of these isolates proved that they were Citrobacter ferundii and Proteus mirabilis. The antimicrobial activity for Lactobacillus acidophilus ATCC 4356 and Streptococcus thermophiles ATCC 19987 mixture and their cell-free supernatant mixture were activated by low doses of gamma radiation (5 Gray for lactic acid bacteria & 20 Gray for supernatant). Results proved that on applying the two previously activated mixtures on chicken carcasses, supernatants completely killed the three pathogens (Citrobacter ferundii, Proteus mirabilis and Salmonella typhi ATCC 14028 reference strain) during 4 hours while the lactic acid bacteria mixture killed them after 3 hours.