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Bacterial Exposure to Low Dose Radiation Followed by a High Dose Can Threaten Effective Treatment of Infections Through Inducing Adaptive Responses

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S Mortazavi

S Mortazavi1*, M Taheri2 , b karari3 , F Habibi4 , M Zehtabiyan5 , (1) Shiraz University of Medical Sciences, Shiraz, Fars, (2) Hamadan University of Medical Sciences, Hamadan, Hamadan, (3) Shiraz University, Shiraz, Fars, (4) Shiraz University, Shiraz, Fars, (5) Shiraz University, Shiraz, Fars


SU-I-GPD-T-636 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: All creatures live in in an environment filled with a wide range of ionizing and non-ionizing radiations.. According to WHO, antimicrobial resistance is a growing serious threat to global human health. WHO believes that antimicrobial resistance threatens the effective prevention and treatment of bacterial infections. While high levels of gamma radiation are widely used for sterilization, there are controversial reports on the effect of low levels of ionizing radiation on the proliferation and drug resistance of different bacteria. This study was designed to investigate the pattern of susceptibility of bacteria to antibacterial agents after exposure to low and high doses of x and gamma rays.

Methods: Exposure groups of Staphylococcus and Escherichia were exposed to 1cGy x and gamma radiations generated by a Siemens industrial fluoroscopy and a Cs-137 source, respectively. Control groups were only sham-irradiated. In the next stage, 40, 90 and 200 min after the low dose exposure, culture plates were exposed to 1Gy x or gamma radiation. Antibiogram tests were performed immediately after receiving the high dose.

Results: While there were only slight differences between the diameters of inhibition zones in control and 1 Gy-exposed groups, the inhibition zones for bacteria exposed to both 1cGy and 1Gy doses were significantly less than those of the bacteria only exposed to 1 Gy. Furthermore, it was shown that a time interval of 200 min between the low dose and high dose exposures depicted the highest magnitude of induced adaptive-responses. Altogether, these findings indicate that pre-exposure of these bacteria to x and gamma radiation increases their resistance to various antibiotics.

Conclusion: These results clearly show that the adaptive responses induced by a pre-exposure to low dose radiation followed by a high dose can threaten the effective treatment of bacterial infections.

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