Unravelling the Diversity and Abundance of the Red Fox (Vulpes vulpes) Faecal Resistome and the Phenotypic Antibiotic Susceptibility of Indicator Bacteria

Abstract

The WHO considers that antimicrobial resistance (AMR) is among the ten greatest global public health risks of the 21st century. The expansion of human populations and anthropogenically related activities, accompanied by the fragmentation of natural habitats, has resulted in increased human–wildlife interaction. Natural ecosystems are therefore subjected to anthropogenic inputs, which affect the resistome of wild animals. Thus, urgent multisectoral action is needed to achieve the Sustainable Development Goals following the One Health approach. The present work falls within the scope of this approach and aims to characterize the AMR of the faecal microbiome of the red fox (Vulpes vulpes), an opportunistic and generalist synanthropic species whose abundance has been increasing in urban and peri-urban areas. A high number of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) were screened and quantified using a high-throughput qPCR approach, and the antimicrobial susceptibility of cultivable E. coli and Enterococcus spp. were assessed interpreted with both ECOFFs and clinical breakpoints. The most abundant ARGs detected confer resistance to trimethoprim and tetracyclines, although the first were absent in one of the locations studied. Several ARGs considered to be threats to human health were identified in high relative abundances (blaTEM, ermB, aadA, tetM, tetW, tetL, drfA1 and drfA17), especially in the geographical area with greater anthropogenic influence. Although at a low percentage, resistant and multidrug-resistant (MDR) E. coli and Enterococcus spp. were isolated, including one MDR E. coli showing resistance to 12 antimicrobials from 6 different classes.

Antimicrobial Resistance in Enterococcus spp. Isolates from Red Foxes (Vulpes vulpes) in Latvia

“…The percentage of identified Enterococcus spp. isolates that were resistant to at least one antimicrobial agent was lower than 73% in Portugal [37] and Italy, where 35% of all isolates were susceptible to all the tested antimicrobial agents [38]. In the present study, no MDR isolates were found that resulted in a conflicting finding with those of previous authors, who reported the prevalence of MDR in Enterococcus from 3% in red foxes in Portugal [37] to 63% in wild Pampas foxes (Lycalopex gymnocercus) in Brazil [35].…”

“…The identified high rates of antimicrobial resistance in Enterococcus spp. to tetracycline, erythromycin, and ciprofloxacin were in agreement with the findings of previous research on Carnivora [36][37][38]. Resistance to tetracyclines and ciprofloxacin in Enterococcus spp.…”

“…tet(M) was the predominant gene in our study among tetracycline-resistant isolates, and was among the most frequently identified genes conferring resistance to tetracyclines [52]. tet(M) was among the most abundant ARGs in red foxes in Spain and other carnivores-otters (Lutra lutra) in Portugal, racoon dogs (Nyctereutes procyonoides Gray, 1834), American minks (Neovison vison Schreber, 1777), and beech martens (Martes foina) in Poland [29,37,50]. Two E. faecalis isolates showed high-level resistance to tetracyclines, with a MIC ≥ 128, and one isolate with resistance to tetracycline was associated with the presence of the high-level streptomycin resistance gene ant(6)-Ia and the tet(M) and tet(L) genes.…”

“…Almost every Enterococcus isolate from wildlife carnivores shares the MDR patterns identified for wildlife carnivores in Poland [29]. It has been suggested that the proximity of foxes to human habitats, rural colonization, and the urbanization of foxes sharing the same habitat as humans may promote the distribution of antimicrobial resistance and infectious agents [37,39]. In the present study, the samples mostly originated from remote areas with a low population density; thus, limited access to antimicrobial exposure may have reduced the ability of the faecal microbiota to develop antimicrobial resistance [40].…”

Bidirectional Interaction between Tetracyclines and Gut Microbiome

“…During tetracycline treatment, there is a decrease in the abundance of susceptible bacteria, which can lead to an overgrowth of antibiotic-resistant bacteria [ 88 , 89 , 90 , 91 ]. This overgrowth can result in the development of antibiotic-associated diarrhea, which is a common side effect of tetracycline treatment.…”