A total of 9 different bacteria species (see "exposed system") with different gram staining characteristics and shapes were used. Bacteria of each species were assigned to the following groups: 1) exposure to a 5 Hz magnetic field with 25 mT, 2) exposure to 25 Hz magnetic field with 29 mT, 3) exposure to a 50 Hz magnetic field with 34 mT, 4) exposure to a 50 Hz magnetic field with 34 mT and further incubation without exposure for 300 minutes, 5) sham exposure and 6) control group. The control group was conducted simultaneously to an actual exposure in the reserve water bath, which was used to maintain the temperature in the exposure generator.
|Chamber||15 ml polypropylene tubes|
|Setup||setup contained generator for the field, which was made of a three-phase stator of an induction squirrel cage motor, and a water bath incubator (glass container) for the tubes with bacteria placed inside it during the exposure; the glass container was axially aligned with the generator and positioned symmetrically with respect to its lower and upper ends; temperature in the water bath remained constant at 37 ± 0.5°C|
|Sham exposure||A sham exposure was conducted.|
Growth rate, metabolic activity and biofilm formation were significantly increased in S. aureus, E. coli, S. marcescens, S. mutans, C. sakazakii, K. oxytoca and S. xylosus cultures compared to the control group immediately after exposure. However, the metabolic activity and biofilm formation were significantly impaired in A. baumannii and P. aeruginosa cultures. The most distinct effects were found after an exposure to the 50 Hz field with 34 mT (group 3).
300 minutes after exposure (group 4), no significant differences were detected in comparison to the control group anymore. Also no significant differences could be found between the sham exposure group and control group.
The authors conclude that exposure of bacteria to extremely low frequency magnetic fields could affect growth, metabolic activity and biofilm formation depending on the exposed species and frequency and strength of the field.