JOIN USRepelling forces In a shocking development, it has been found that many harmful bacteria are turning immune to antibiotics. But researchers have found a way to deal with it, reports Madhukara Putty
Earth is home to billions of bacteria, most of which are harmless. In fact, without nitrogen fixation, a process performed seamlessly by bacteria, proteins wouldn’t have synthesised, and life wouldn’t have flourished at all. Similarly, some other bacteria come handy in sewage treatment and the production of cheese and yogurt.
However, not all are friendly in nature. There is a small portion of bacteria that can trouble humans, and sometimes, even cause death. Tuberculosis, an infectious disease, which kills millions of people in developing countries, is caused by bacteria. However, the bigger concern is that these bacteria have learnt to adapt to antibiotics.
According to World Health Organization (WHO), in 2013 alone, there were about five lakh cases of tuberculosis, in which the bacteria simply refused to get bogged down by a number of antibiotics. WHO warns that without urgent, co-ordinated action, the world is heading towards a post-antibiotic era, in which common infections and minor injuries, which have been treatable for decades, can once again kill.
Combining biology and physics
Thus, the need of the hour is to find innovative ways to curtail bacterial growth, and avert a looming public health crisis. The researchers from the Indian Institute of Science (IISc), Bengaluru have done exactly that. They have developed a way to kill bacteria using dynamic magnetic fields. The research effort was led by Bikramjit Basu, professor, materials research centre, IISc, and Deepak K Saini, assistant professor, department of molecular reproduction, development and genetics, IISc.
“We were interested in devising a non-invasive biophysical method to curb bacterial infections. A few reports had suggested that bacterial death occurred when exposed to moderate intensity and low frequency magnetic fields. Further, theoretical models had been proposed to explain the detrimental effects of magnetic fields on bacterial growth and survival.
Hence, we were keen to investigate if high strength pulsed magnetic field can lead to bacterial inactivation without affecting native mammalian cells or tissues,” says Sunil Kumar Boda, who participated in the study.
A magnet can attract or push away other magnets in its vicinity, depending on their relative orientations. The force that attracts or repels the other magnet is a manifestation of an abstract quantity called the magnetic field. The IISc researchers used pulsed magnetic fields to kill the infecting bacteria.
Unlike the magnetic field we experience in normal magnets, pulsed magnetic fields change with time: they are stronger for some duration and weaker for some duration. The researchers conducted their preliminary trials on infectious bacteria, as well as mouse and human cells.
The team studied the effect of pulsed magnetic field on pathogenic Staphylococcus species associated with biomaterial infections, and on Escherechia coli — a strain of bacteria commonly found in the intestine of mammals. They found that more than half of the Staphylococcal species bacterial load was eliminated when exposed to strong pulsed magnetic field and the population of E.coli was reduced to about 70 per cent.
The Staphylococcal species also exhibited a reduction in growth rate, which was attributed to an increase in levels of damaging free radicals such as Reactive Oxygen Species (ROS) with increasing Pulsed Magnetic Field (PMF) strength. Free radicals like ROS are molecules that possess one or more free electrons and are usually unstable, thus, making them highly reactive in nature. They are the primary mediators of damage to various constituents of cells such as DNA, protein etc.
Though the magnetic field was very efficient in killing bacteria, it was not so good with human cells, fortunately. As Bikramjit puts it, “One of the positives of our study is the differential survival of bacteria and mammalian cells when exposed to PMF. While 60-70 per cent of the bacteria were injured, a much milder decrease in mammalian cell survival was recorded under identical PMF exposure.”
One of the limitations of this method is the heat produced while generating PMF.
In the experimental design, to reduce the heating effects, the cultures were intermittently exposed to PMF at intervals of three-five minutes. This, however, facilitates partial recovery of the damaged bacteria.
It is expected that a more efficient cooling system would allow for more frequent exposure of the bacterial cultures to PMF, thereby achieving more lethal effect on the bacteria. “For a realistic clinical application, PMF can be coupled with traditional antimicrobial therapies, in order to prevent infection and hasten wound healing,” says Deepak.
“In the context of PMF, our next plan is to formulate a biophysical model for bacteria-magnetic field interaction that can theoretically explain our experimental observations,” ends Sunil.