3.1 Temporal evolution of scientific research
Publications dated from 1979 to 2019 and, overall, the temporal trend in publication on antimicrobial resistance in wildlife shows a growth in the number of documents published per year, with an annual percentage growth rate of 7,2% (Figure 2). The global evolution of literature can be split into two periods, exhibiting kind of a diauxic growth: from 1979 to 2008, the scientific literature increased slowly (only 47 publications). However, from 2009 to 2019, the growth was steady and swift; 78% of the research papers were published in the last ten years. This indicates that this research topic has attracted particular interest (and perhaps funding) in the last decade, likely a reflex of the increase of global importance of the AMR subject as more countries and institutions began to devote themselves to this topic. The maximum number of documents on AMR in wildlife was published in 2018, with a total of 20 publications, but 2019 should follow the same trend as the database was last updated in November, accounting already 17 publications. This rejuvenated interest in AMR research in wildlife can be attributed to the fact that three of the most cited research in AMR in wildlife were published in previous years and in relevant journals (Table 1). Additionally, and perhaps more importantly, since the first studies regarding antibiotic resistance in wildlife, a discussion started whether resistance in wildlife was or not related with human use (Gilliver et al., 1999; Österblad  et al., 2001). Gilliver et al. (1999) detected high prevalence of bacteria with antibiotic resistance from wild rodents living in rural areas in Wirral, northwest England, in areas with absent or minimum levels of released antibiotics. Such fact led Gilliver et al. (1999) to claim that the found prevalence was not directly a result of anthropogenic impact and that antibiotic use restrictions would have marginal effect of wildlife reservoirs. Contrastingly, Österblad et al. (2001) described almost no resistance in bacteria recovered from moose, deer and voles in pristine areas of Finland. These two seminal papers brought into debate the effects of human proximity, highlighting the importance of understanding the role of wildlife in the ecology of antibiotic resistance. Since then, research has been focused on untangling the routes of transmission between humans and wildlife, reinforcing the idea that the same antimicrobial resistance patterns co-occur in wildlife, livestock and human populations. For example, beta-lactamases that inactivate the action of beta-lactam antibiotics (e.g. penicillin), one of the most important group of antimicrobial agents used in human and veterinary medicine, are now frequently found in bacterial isolates from wildlife (Guenther et al., 2011), particularly birds and mammals (Silva et al., 2011; Goncalves et al., 2013), as well as in livestock and environmental samples.