ESBL/AmpC-Producing Escherichia coli in Wild Boar: Epidemiology and Risk Factors

Simple Summary Antimicrobial resistance (AMR) represents a complex global issue due to the many factors involved. Extended-spectrum beta-lactamase and AmpC (ESBL/AmpC)-producing Escherichia coli deserves attention for its broad repercussions on public health. Moreover, wild host species are of interest, particularly wild boar. Indeed, the constantly increasing population densities and the limited data on AMR in this species lead to health risks where spatial overlap with humans and domestic animals occurs. Therefore, 1504 wild boar fecal samples were analyzed to investigate ESBL/AmpC-producing E. coli and the effects of host-related factors and of human population density on their spread. A high prevalence of ESBL/AmpC-producing E. coli emerged in wild boar, species not treated with antibiotics, supporting that infection may be acquired through environmental contamination, whether of human or animal origin. Young animals were more colonized than older ones, demonstrating higher susceptibility as seen in domestic animals. Moreover, a positive association recorded between frequency of the TEM resistance gene and human population density suggests that spatial overlap may influence the infection in wild boar. Further analyses would be desirable to investigate the origin of the recorded environmental contamination, although a role of wild boar as a maintenance host of AMR strains emerged. The complex health problem of antimicrobial resistance (AMR) involves many host species, numerous bacteria and several routes of transmission. Extended-spectrum beta-lactamase and AmpC (ESBL/AmpC)-producing Escherichia coli are among the most important strains. Moreover, wildlife hosts are of interest as they are likely antibiotics free and are assumed as environmental indicators of AMR contamination. Particularly, wild boar (Sus scrofa) deserves attention because of its increased population densities, with consequent health risks at the wildlife-domestic-human interface, and the limited data available on AMR. Here, 1504 wild boar fecal samples were microbiologically and molecularly analyzed to investigate ESBL/AmpC-producing E. coli and, through generalized linear models, the effects of host-related factors and of human population density on their spread. A prevalence of 15.96% of ESBL/AmpC-producing E. coli, supported by bla(CTX-M) (12.3%), bla(TEM) (6.98%), bla(CMY) (0.86%) and bla(SHV) (0.47%) gene detection, emerged. Young animals were more colonized by ESBL/AmpC strains than older subjects, as observed in domestic animals. Increased human population density leads to increased bla(TEM) prevalence in wild boar, suggesting that spatial overlap may favor this transmission. Our results show a high level of AMR contamination in the study area that should be further investigated. However, a role of wild boar as a maintenance host of AMR strains emerged.

Automated summary

The issue of antimicrobial resistance (AMR) is complex and involves factors such as ESBL/AmpC-producing Escherichia coli in wildlife hosts, particularly in wild boar, with higher infection rates in young animals. A positive association was found between human population density and resistance gene frequency in wild boar, suggesting spatial overlap may influence infection. Further investigation is needed to understand the origin of environmental contamination and the role of wild boar as a maintenance host of AMR strains.