Abstract
The objective of the study was to examine a population of free-living carnivorous mammals most commonly found in Poland (red fox, beech marten, and raccoon) for the occurrence of bacteria that are potentially pathogenic for humans and other animal species and to determine their virulence potential (the presence of selected virulence genes). From the total pool of isolates obtained (n = 328), we selected 90 belonging to species that pose the greatest potential threat to human health: Salmonella spp. (n = 19; 4.51%), Yersinia enterocolitica (n = 10; 2.37%), Listeria monocytogenes and L. ivanovii (n = 21), and Staphylococcus aureus (n = 40; 9.5%). The Salmonella spp. isolates represented three different subspecies; S. enterica subsp. enterica accounted for a significant proportion (15/19), and most of the serotypes isolated (S. Typhimurium, S. Infantis, S. Newport and S. Enteritidis) were among the 10 non-typhoidal Salmonella serotypes that are most often responsible for infections in Europe, including Poland. Y. enterococlitica was detected in the smallest percentage of animals, but 60% of strains among the isolates tested possessed the ail gene, which is responsible for attachment and invasion. Potentially pathogenic Listeria species were isolated from approx. 5% of the animals. The presence of all tested virulence genes was shown in 35% of L. monocytogenes strains, while in the case of the other strains, the genes occurred in varying numbers and configurations. The presence of the inlA, inlC, hlyA, and iap genes was noted in all strains, whereas the genes encoding PI-PLC, actin, and internalin Imo2821 were present in varying percentages (from 80% to 55%). S. aureus was obtained from 40 individuals. Most isolates possessed the hla, hld (95% for each), and hlb (32.5%) genes encoding hemolysins as well as the gene encoding leukotoxin lukED (70%). In a similar percentage of strains (77.5%), the presence of at least one gene encoding enterotoxin was found, with 12.5% exhibiting the presence of egc-like variants. In two animals, we also noted the gene encoding the TSST-1 toxin. The results of the study showed that free-living animals may be a significant reservoir of bacteria that are potentially pathogenic for humans. The results of the statistical analysis revealed that, among the animals species studied, the red fox constitutes the most important source of infections.
Highlights
Free-living animals have always been a significant source of infectious diseases transmitted to humans
The tests conducted on 421 animals made it possible to distinguish 328 isolates belonging to the genera Salmonella, Staphylococcus, Listeria, and Yersinia (Table 1)
The coagulase-positive Staphylococcus spp. were isolated most frequently (60.33%; CI: 27.8–35.53), while the presence of the other bacteria was detected in a smaller number of animals: Listeria spp. 7, 36%; (CI: 4.71–5.65), Yersinia spp. 5.7% (CI: 3.12–5.58), and Salmonella spp. 4.51% (CI: 1.31–6.2) (Table 1)
Summary
Free-living animals have always been a significant source of infectious diseases transmitted to humans. Free-living carnivorous animals are a permanent biocoenotic element that is highly diverse in terms of adaptation to the environment; in general, they have outstanding migratory potential associated with an active search for food These predators live in environments without people, and appear in areas populated by humans, in the winter or spring when there is considerably less available food [2]. Species such as the red fox, beech marten, or raccoon constitute a relatively large percentage of the population of free-living carnivorous animals in Poland. The most serious problem is their invasion into protected natural areas, which is one of the reasons why raccoons are game animals that can be hunted year round with no closed season
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