New York:Researchers have found that combinations of three different antibiotics can help overcome bacteria's resistance to antibiotics, even when none of the three antibiotics on their own, or even two of the three together, is effective. For the study, the researchers grew E. coli bacteria in a laboratory and treated the samples with combinations of one, two and three antibiotics. They found that out of the 364 three-drug combinations the researchers tested, 94 killed 100 per cent of the bacteria. The success rate might have been even greater if the researchers tested higher doses of the drugs, said Pamela Yeh, Assistant Professor at University of California, Los Angeles (UCLA). "Three antibiotics can change the dynamic. Not many scientists realise that three-drug combinations can have really beneficial effects that they would not have predicted even by studying all pairs of the antibiotics together," added lead author Elif Tekin, graduate student at UCLA. With a group of 14 drugs, the researchers determined that when adding a third antibiotic new effects that combinations of just two drugs couldn't achieve were produced. As different classes of antibiotics use different mechanisms to fight bacteria, they combined techniques from biology and mathematics to determine which groups of antibiotics would be most effective. "The three antibiotics must be chosen systematically and rationally," Yeh noted. The findings could be one weapon to fight what has become a major public health risk, but overcoming drug resistance will require a need sound policy, the researchers said. Another benefit of three-drug combinations is that they could allow doctors to prescribe lower doses of each antibiotic, which could reduce side effects. Further, the study provide new hope for the nearly 700,000 people who die each year due to infection from drug-resistant bacteria, including carbapenem-resistant Enterobacteriaceae such as E. coli. The results appear in the journal Royal Society Interface.