London – A new research shows dangerous mcr-1 gene, which provides resistance to the last-resort antibiotic colistin, has been found in four healthy humans and two pet dogs. The study raises concerns that pets can act as reservoirs of the gene and so aid the spread of resistance to precious last-line antibiotics, said researchers from the University of Lisbon. They found two cases, in which both dog and owner were harbouring the gene. The mcr-1 gene, first reported in China in 2015, confers resistance to colistin — an antibiotic of last resort used to treat infections from some bacteria resistant to all other antibiotics. Juliana Menezes from the varsity’s Centre of Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, said: “Colistin is used when all other antibiotics have failed — it is a crucial treatment of last resort. If bacteria resistant to all drugs acquire this resistance gene, they would become untreatable, and that’s a scenario we must avoid at all costs. We know that the overuse of antibiotics drives resistance and it is vital that they are used responsibly, not just in medicine but also in veterinary medicine and in farming.” Samples were taken from 126 healthy people living with 102 cats and dogs in 80 households in Lisbon between February 2018 and February 2020. All of the humans and 61 of the pets were healthy. While transmission in both directions is possible, it is thought that in this case, the gene passed from dog to human, Menezes said. The owners did not have infections and so did not need treatment. The sick dogs were successfully treated.