Safety Assessment of Fecal, Bacteriocin-Producing Strains Enterococcus mundtii from Horses

Abstract

Backround: Knowing and optimizing the host microbiota is important regarding the maintenance of horse`s health. For this approach beneficial bacteria have been usually used. However, to be the most effective in use, their safety, tolerability and efficacy needs to be assessed. Therefore, fecal strains Enterococcus mundtii from horses with promising bacteriocinogenic potential have to be evaluated for their safety. Methodology: E. mundtii strains were isolated from feces of 47 horses (n=47; 40 mares and seven stallions), the Norik breed from Muráň in eastern Slovakia. MALDTI-TOF spectrometry and sequencing were used. Phenotypic characteristics were assessed in accordance with those for the reference strain E. mundtii ATCC43186. Biofilm-forming ability was tested using plate assay. For enzyme production commercial tests were applied and virulence factor genes were tested using PCR and primers. Antibiotic profile was tested with diffusion method. In vivo safety was tested using Balb/c breed mice. Results: E. mundtii strains did not produce the enzyme β-glucuronidase; however, most E. mundtii strains produced β-galactosidase. The strains were absent of virulence factors such as gelatinase, aggregation substance, cytolysin A, enterococcal superficial protein, adhesins, hyaluronidase and IS16 element, except efaAfs gene in the strain EMKD 24/1. Six strains were found with lowgrade (0.1 ≤ A570< 1) biofilm - forming ability. E. mundtii were mostly susceptible to antibiotics. Bacteriocinogenic strain EMKD41/3 reached high counts in feces (5.12 ± 0.26 CFU/g log 10) of Balb/c mice during its 30 days application. No mortality of mice was noted during whole period of EMKD41/3 strain application. Conclusion: Bacteriocin-producing strains E. mundtii should not threaten horses because they were mostly susceptible to antibiotics, they were virulence factor genes absent and with low-grade biofilm formation ability. Bacteriocinproducing strain EMKD41/3 even indicates its sufficient implementation in host organism with any side effect.