Three species of potentially pathogenic amoebae between 0.8 and 2.5 mT [Ramon et al., 1987]. Growth of Micrococcus denitrificans and Saccharomyces cere-were exposed to 71 and 106.5 mT from constant homogenous magnetic fields and examined for inhibition visiae also increased in homogeneous magnetic fields of 0.5 -0.8 T [Thiemann and Wagner, 1970]. Using of population growth. The number of amoebae for three species was significantly less than controls after a several bacterial species and Candida, Moore [1979] reported that a magnetic field of 15 mT stimulated 72 h exposure to the magnetic fields when the temperature was 20 ΠC or above. Axenic cultures, i.e., cultures growth of the organism but inhibited growth at 30 -60 mT, and static magnetic fields were most inhibi-grown without bacteria, were significantly affected after only 24 h. In 20 of 21 tests using the three species, tory. Hedrick [1964] observed that Staphylococcus aureus growth was inhibited after 15 h in a homoge-the magnetic field significantly inhibited the growth of amoebae. In one test in which the temperature was neous constant magnetic field of 1.4 T and that variable fields created by removing the bacteria from the mag-20 ΠC for 48 h, exposure to the magnetic field was not inhibitory. Final numbers of magnetic field-exposed netic field for 3 s every hour had no effect. S. lutea and Escherichia coli, however, were not affected by amoebae ranged from 9 to 72% lower than the final numbers of unexposed controls, depending on the spe-the 1.4 T. Growth of Serratia marcescens and S. aureus exposed to 0.8 -1.5 T was inhibited at 6-7 h of mag-cies. This research may lead to disinfection strategies utilizing magnetic fields for surfaces on which patho-netic field exposure, but, by 10 h, there was no longer an inhibitory effect on growth [Gerencser et al., 1962]. genic amoebae may proliferate.
In the 1970s, active research in health effects of Okuno et al. [1993] used high magnetic fields of 11.7 T to stimulate growth of E. coli. The use of high magnetic magnetic fields mainly involved therapeutic and diagnostic uses, such as magnetic control devices and use fields was suggested for inactivating bacteria and fungi in the food industry [Pothakamury et al., 1993]. of ferromagnetic particles for tracing blood circulation [Frei, 1972]. Currently, there is great concern about To date, however, there are no studies on magnetic fields and amoebae. The present study examined health effects from electromagnetic fields generated by power lines and home appliances [Moore, 1990; Perry, the inhibitory effect of static uniform magnetic fields on the population growth of three species of amoebae. 1994]. Most of the published studies of effects of magnetic fields on microorganisms are inconclusive, re-The objective was to determine whether magnetic fields could inhibit the growth of amoebae. Such research porting inhibitory effects, stimulatory effects, or both, may lead to development of disinfection strategies for depending on conditions. surfaces, such as contact lenses, on which pathogenic Jennison [1937], by using bacteria and yeast, amoebae may proliferate. studied colony size, size and shape of individual cells, Acanthamoeba hatchetti was isolated from an air Gram-stain reaction, and pigment or spore production of cultures exposed to magnetic fields. In that study, magnetic fields did not alter such characteristics of *Correspondence to: Sharon G. Berk, Center for the Management, Utili- these organisms. Changes in growth rates of microorzation and Protection of Water Resources, P.O. Box 5033, Tennessee