The effects of different intensities, frequencies and exposure times of extremely low-frequency electromagnetic fields on the growth of Staphylococcus aureus and Escherichia coli O157:H7

Abstract

The impact of different types of extremely low-frequency electromagnetic fields (ELF-EMF) on the growth of Staphylococcus aureus and Escherichia coli O157:H7 was investigated. The cultures of bacteria in broth media were exposed to sinusoidal homogenous ELF-EMF with 2 and 4 mT magnetic intensities. Each intensity for each bacteria was combined with three different frequencies (20, 40 and 50 Hz), and four different exposure times (1, 2, 4 and 6 h). A cell suspension of each experiment was diluted for the appropriate range and inoculated to Mueller–Hinton Agar (MHA) plates after exposure to ELF-EMF. The number of colony forming units (CFU) of both strains was obtained after incubation at 37 °C for 24 h. Data were statistically evaluated by one-way analysis of variance (ANOVA), statistical significance was described at p < 0.05 and data were compared with their non-exposed controls. Magnetic intensity, frequency and exposure time of ELF-EMFs changed the characteristic responses for both microorganisms. Samples exposed to ELF-EMF showed a statistically significant decrease compared to their controls in colony forming capability, especially at long exposure times. An exposure to 4 mT–20 Hz ELF-EMF of 6 h produced maximum inhibition of CFU compared to their controls for both microorganisms (95.2% for S. aureus and 85% for E. coli).

• Bacteria
• Escherichia coli
• extremely low-frequency electromagnetic field
• Staphylococcus aureus

Acknowledgments

We thank Assist. Prof. Dr Ömer Mermer, Assist. Prof. Dr Yavuz Öztürk and Dr Serhat Küçükdermenci for their help in ELF-EMF applications and Ahmet Yalın Bayır for helping to draw the illustration of the electromagnet.

Declaration of interest

This work supported by The Scientific and Technological Research Council of Turkey (TUBITAK) within the funding programme 2209. The authors declare no conflict of interests. The authors alone are responsible for the content and writing of the article.