New Delhi, April 16 : Scientists have identified several protective drugs that may lessen the collateral damage caused by antibiotics without compromising their effectiveness against harmful bacteria. The researchers identified several promising drugs including the anticoagulant dicumarol, the gout medication benzbromarone, and two anti-inflammatory drugs, tolfenamic acid and diflunisal. Importantly, these drugs did not compromise the effectiveness of the antibiotics against disease-causing bacteria. Antibiotics help to fight bacterial infections, but they can also harm the helpful microbes living in the gut, which can have long-lasting health consequences. The study by Dr Lisa Maier and Dr Camille V Goemans from the European Molecular Biology Laboratory, Heidelberg, Germany and colleagues, analysed the effects of 144 different antibiotics on the abundance of the most common gut bacteria, offers novel insights into reducing the adverse effects of antibiotic treatment on the gut microbiome. The study is set to be presented at European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Copenhagen, Denmark (April 15-18). The researchers systematically analysed the growth and survival of 27 different bacterial species commonly found in the gut following treatment with 144 different antibiotics. They also assessed the minimal inhibitory concentration (MIC) - the minimal concentration of an antibiotic required to stop bacteria from growing - for over 800 of these antibiotic-bacteria combinations. The results revealed that the majority of gut bacteria had slightly higher MICs than disease-causing bacteria, suggesting that at commonly used antibiotic concentrations, most of the tested gut bacteria would not be affected. However, two widely used antibiotic classes -- tetracyclines and macrolides -- not only stopped healthy bacteria growing at much lower concentrations than those required to stop the growth of disease-causing bacteria, but they also killed more than half of the gut bacterial species they tested, potentially altering the gut microbiome composition for a long time. "Despite our promising findings, further research is needed to identify optimum and personalised combinations of antidote drugs and to exclude any potential long-term effects on the gut microbiome," said Dr Ulrike Lober, of the Max-Delbruck-Center for Molecular Medicine in Berlin, Germany who is presenting the research at ECCMID. /IANS