Gamma Irradiation Increases the Sensitivity of Salmonella to Antibiotics

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Author(s) Najla Ben Miloud Yahia | Alya El May | Salma Helel | Imed Maatouk | Abdelweheb Chatti | Mouldi Saidi | Ahmed Landoulsi
Pages 279-288
Volume 4
Issue 6
Date June, 2015
Keywords Gamma Irradiation, Salmonella, Antibiotic Susceptibility, Oxidizing Stress, Diameter of the Inhibition Zone.

The present study was carried out to evaluate the effects of non-lethal gamma irradiation on antibiotic sensitivity of Salmonella. Four isolates representative of three serotypes collected from foods were treated with sub-lethal gamma radiation doses to induce cell damage. Antibiogram analysis was performed immediately after irradiation treatment. Our results showed a significant sensitivity increase (P<0.01) of the four Salmonella isolates to cefalotin, chloramphenicol and gentamicin after irradiation at 1 kGy with a significant dose effect at 2 kGy for all or some of these antibiotics depending on the isolate. In one isolate and for cefalotin the ionizing treatment led to a shift from resistance to sensitivity at 1 kGy. In a second isolate an increase of sensitivity was also observed for spiramycin at 2 kGy (p<0.001) and erythromicyn at 1 and 2 kGy (p<0.05) compared to controls. An increase of sensitivity to penicillin and tetracyclin was observed in a third isolate at 1 kGy with a dose dependent effect at 2 kGy (p <0.001). The gamma irradiation did not affect the diameter of the inhibition zone of oxacillin and vanconmycin in the four isolates and that of penicillin, nalidixic acid, erythromycin and tetracyclin in some isolates. These data suggest a possible stress response to gamma irradiation with a differential behaviour with regard to the Salmonella isolates. The variability of the radiation effect on susceptibility towards the different antibiotics could be explained by the nature, the penetration mode inside the cell or by the action way of the antibiotics.

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