Multilocus sequence typing, antibiotic resistance, and virulence genes of Enterococcus faecalis from sheep

Abstract:

[Background] As a common opportunistic pathogen, Enterococcus faecalis can cause severe infections and pose a serious threat to public safety as a carrier of high resistance/virulence factors. [Objective] To master the sequence type (ST) distribution, antibiotic resistance, and virulence of sheep-derived E.faecalis strains in Anhui Province, analyze the correlations of antibiotic resistance and virulence genes with ST, and evaluate the potential threat to the public health. [Methods] E.faecalis was isolated from 64 sheep anal swab samples collected from Anhui during 2021−2023. Multilocus sequence typing (MLST) was employed to classify and identify the isolates. Kirby Bauer (K-B) test was carried out to determine the sensitivity of E.faecalis isolates to 16 antibiotics. Furthermore, the distribution of 9 resistance genes and 14 virulence genes was tested. [Results] A total of 61 strains of E.faecalis were isolated and identified as 24 STs, of which 9 were newly discovered STs. Most of the strains showed resistance to netilmicin (72.13%), amikacin (75.41%), tetracycline (55.74%), and erythromycin (63.93%). A few strains were resistant to vancomycin (9.84%) and linezolid (11.48%). with And the multi-drug resistance (MDR) rate was 57.38%. The carrier rates of resistance genes ermB (77.05%), aac(6')/aph(2') (52.46%), and tem (55.74%) were high, while those of vanC and mefA were low at 8.20% and 1.64%, respectively. The carrying rates of virulence genes cpd (100%), efaA (98.36%), ebp (95.08%), and fsr (81.97%) were high, while it was the lowest for hyl (11.48%). The distribution of some resistance and virulence genes showed differences among different STs (P<0.05). [Conclusion] Enterococcus faecalis from sheep feces carry high resistance and high virulence genes, and the distribution of resistance and virulence is highly correlated with STs.

Key words:Enterococcus faecalis;multilocus sequence typing;resistance characteristics;virulence genes