Antimicrobial resistance in wild boar in Europe: Present knowledge and future challenges

© Cambridge University Press 2018. Natural and Anthropogenic Niches of Antimicrobial Resistance Antimicrobials are essential for the treatment of bacterial infections in humans and animals. However, their intensive use (and misuse) has severely increased the frequency of resistance among clinical and environmental bacteria, with progressively less effective therapies, and a post-antibiotic era is predicted (Woolhouse & Farrar 2014). Antimicrobial resistance (AMR) is nowadays an obstacle to the treatment of infectious diseases, posing a significant threat to public health. Antibiotics underpin routine medical practice, and thus monitoring and reporting their occurrence must remain a priority for health agencies worldwide. In terms of economy, their impact is huge and the global human burden posed by infections is difficult to quantify, but 25,000 deaths and €1.5 billion in economic losses are estimated in the EU alone for each year (EMA & ECDC 2009). As a result, the World Health Organization has identified AMR as a global, emerging, unparalleled and growing problem for public, animal, and environment health (WHO 2014). When a microorganism that was susceptible to an antibiotic is no longer sensitive to it, resistance becomes acquired, making antibiotics less effective and limiting treatment options. This acquired resistance phenotype contrasts with natural resistance displayed by several bacteria, in which resistance mechanisms probably evolved to protect these bacteria against their own produced molecules and against antibiotics that are naturally produced in their ecological niches by other competing microorganisms (D’Costa et al. 2007). Indeed, soil environmental bacteria have been producing antibiotics for probably 2 billion years (D’Costa et al. 2011). Soil is thus considered to be the original source of bacteria naturally producing most of the antimicrobial molecules used nowadays in medicine and veterinary settings (D’Costa et al. 2007). The first reports of resistance have usually arisen during clinical trials and resistance typically increases during the lifetime of an antibiotic. In the early beginnings of this acquired resistance phenomenon, alternative classes of antibiotics to which bacteria had not yet developed resistance were always around. Multiple drug resistance (MDR), i.e. resistance to multiple antibiotics, were already reported in the late 1950s and early 1960s among common enteric bacteria (Escherichia coli, Shigella, and Salmonella), along with descriptions in the 1970s of Staphylococcus aureus resistance to several classes of antibiotics (methicillin-resistant S. aureus, MRSA).