この研究は、超低周波電磁界（ELF-EMF）の強度、周波数、ばく露時間を変えて、黄色ブドウ球菌およびO157:H7の増殖に対する影響を観察した。肉汁培地中の菌に、正弦波の一様なELF-EMFのばく露（周波数：20、40、50 Hz、強度：2、4 mT、ばく露時間：1、2、4、6時間の組合せ）を与え、ばく露終了後はミューラー・ヒントン寒天培地に植え付けて、24時間培養後のコロニー形成（CFU）の数を無ばく露の対照群と比較した。その結果、2種の菌において、ELF-EMFのばく露への反応の特性は、磁界強度、周波数、ばく露期間によって変化した；ELF-EMFばく露群では、対照群に比べ、コロニー形成力が有意に低下した；特に、ばく露時間が長い群にその傾向が見られた；4 mT、20 Hz、6時間ばく露群で、対照群に比べ、CFUの阻害が最も大きかった（黄色ブドウ球菌で95.2%、大腸菌で85%に低下）、と報告している。
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The effects of exposure of bacteria to different extremely low frequency magnetic fields on cell growth should be investigated.
Bacteria of the strains, Staphylococcus aureus and E. coli, were each exposed to magnetic fields with every combination of 3 different frequencies (20, 40 and 50 Hz) and 2 different magnetic flux densities (2 and 4 mT) for 4 different durations (1, 2, 4 and 6 h). For each exposure condition, a separate sham exposure was conducted and each exposure and respective sham exposure condition was tested 2 times and 4 plates per replicate were counted.
|ばく露1: 20 Hz||
|ばく露2: 40 Hz||
|ばく露3: 50 Hz||
|ばく露4: 20 Hz||
|ばく露5: 40 Hz||
|ばく露6: 50 Hz||
the local geomagnetic field was measured as 32 ± 2.5 µT
|チャンバの詳細||Eppendorf tubes (1.5 ml)|
|ばく露装置の詳細||tubes were placed in the middle of the coils; temperature inside the coil was maintained at 25 ± 0.5°C; no significant temperature change was detected between the activated coils during the trials; the field was homogeneous with a maximum of ± 3.5% deviation|
|Sham exposure||A sham exposure was conducted.|
In both strains and independently from the applied frequency and intensity of the magnetic field, a general trend towards a decreasing cell growth with increasing exposure duration was observed. Except for the exposure duration of 1 hour, which showed inconsistent results, all cells exposed for 2, 4 or 6 hours to a field of 20, 40 or 50 Hz and 2 or 4 mT showed a significantly decreased cell growth compared to the sham exposed cells.
Exposure to a 20 Hz field of 4 mT for 6 h produced the largest decrease in cell growth compared to the sham exposed cells.
The authors conclude that exposure of bacteria to different extremely low frequency magnetic fields could retard cell growth as a function of time.