Title : Antibiotic resistance of Enterococcus spp. strains isolated from wild and farm animals - an important non-clinical problem
Abstract:
The increase in the transfer of pathogenic microorganisms between humans, livestock, wildlife and their environment observed in recent years, as well as the irrational use of antibiotics, makes it increasingly difficult to combat the growing multidrug resistance of bacteria such as Enterococcus spp.
The aim of the study was to evaluate the prevalence and antibiotic resistance of Enterococcus faecalis (EFA) and Enterococcus faecium (EFM) strains isolated from the environment of pig farms and Enterococcus spp. strains isolated from fecal samples of wild animals. Material for the study was collected in a piggeries and within forested areas and ecotone zones in the Kuyavian-Pomeranian Voivodeship. Samples were inoculated onto selective media, and grown bacteria were identified using the MALDI TOF system. Antibiotic susceptibility was assessed using the disc-diffusion method, according to EUCAST recommendations.
In total, 475 and 98 samples were collected from the pig husbandry environment (swabs from troughs, feeding passages and corridors, manure channels, and faeces samples) and from 12 wildlife species (faeces samples), respectively. Of the samples from a pig farm environment, 82 (17.3%) EFA strains and 28 (5.9%) EFM strains were identified. The highest percentage (19.5%) of EFA strains showed resistance to high concentrations of gentamicin (HLGR phenotype), followed by high concentrations of streptomicin (HLSR phenotype) and imipenem (9.8% and 8.5% of strains, respectively). In the case of EFM, an equally high percentage (17.9%) of strains were characterized by the HLGR phenotype and resistance to ampicillin, in addition, 14.3% of strains were resistant to vancomycin (VRE phenotype). In 10.7% of EFM strains was present HLSR phenotype, while 6.1% of EFA was characterized by VRE phenotype. All strains tested showed sensitivity to tigecycline.
Among 92 out of 98 fecal samples from wild animals tested, 118 strains of Enterococcus spp. belonging to 9 species were isolated (EFA, EFM, E. hirae, E. mundtii, E. casseliflavus, E. faecium, E. durans, E. gallinarum., E. avium and E. thailandicus). The most frequently isolated (32.2% of strains) EFA species was
detected in 38 collected samples. The remaining species were isolated with a frequency ranging from 1.0% to 22.4%, among which EFM accounted for 7.6% of the isolated strains. The highest percentage of antibiotic-resistant strains from different chemical groups was found among EFA and EFM. The former was most often resistant to eravacycline (50.0% of strains) and linezolid (39.5% of strains), while EFM was resistant to quinupristin-dalfopristin (44.4% of strains). VRE, HLGR and HLSR phenotypes were found in 13.2%, 31.6% and 2.6% of EFA strains, respectively. In the case of EFM, only the HLGR phenotype was found (11.1% of strains). The lowest percentage (0.9%) among the Enterococcus spp. strains tested was resistant to ampicillin.
The conducted research has shown that both in the pig faeces and various production sectors of the pigsty, as well as in the feces of wild animals, there are microorganisms potentially pathogenic to humans, which may constitute a reservoir of resistance genes to various antibiotics.
