TABLE 1.

Antibacterial spectra of bacteriocins found in Enterococcus faecium KU-B5

Indicator strainAntibacterial activity in culture supernatant (AU/ml)MIC (nM)a
EntAEntBEntXαEntXβEntXα+Xβb
Enterococcus faecalis JCM 5803T1,60064.786.950.8813203e (0.5; 8.0)
Enterococcus faecalis OU5101,60032.3174102813406e (0.5; 4.0)
Enterococcus faecium JCM 5804T200NAfNANANA813c (>16; >16)
Enterococcus faecium TUA 1344L3,20012943.450.881350.8e (2.0; 32)
Enterococcus faecium KU-B5100NANANANA1,630c (>8.0; >8.0)
Enterococcus hirae ATCC 105416,4001295.4450.840650.8e (2.0; 16)
Lactobacillus plantarum ATCC 14917T3,20025986.9102813203e (1.0; 8.0)
Lactobacillus sakei subsp. sakei JCM 1157T12,80016.25.4450.8102203e (0.5; 1.0)
Lactococcus lactis subsp. cremoris ATCC 19257T6,4004,140NA813NA12.7c (130; >1,020)
Staphylococcus aureus subsp. aureus ATCC 12600TNANANANANANA
Streptococcus salivarius JCM 5707TNANANANANANA
Bacillus cereus JCM 2152T400NANANANANA
Bacillus circulans JCM 2504T6,400NANANA3,250813c (>16; 8.0)
Bacillus coagulans JCM 2257T2008,28089,000NA3,2501,630c (>8.0; 4.0)
Bacillus subtilis JCM 1465T4004,14044,500NA3,2501,630c (>8.0; 4.0)
Listeria innocua ATCC 33090T4001,040NA25.43,250406d (0.13; 16)
Micrococcus luteus NBRC 12708NANANANANANA
  • a MICs of enterocin A (EntA), enterocin B (EntB), enterocin Xα (EntXα), enterocin Xβ (EntXβ), and the combination of enterocins Xα and Xβ (EntXα+Xβ), determined by the spot-on-lawn method (21).

  • b The MICs of EntXα+Xβ represent the antibacterial activities of the combination of equimolar amounts of enterocin Xα and enterocin Xβ against a panel of indicator bacteria. The values in parentheses represent two MIC ratios: EntXα/(1/2 × EntXα+Xβ) and EntXβ/(1/2 × EntXα+Xβ). The activity change of at least 4-fold is considered significant. For EntXα and EntXβ, the enterocin with higher activity against a particular bacterium (i.e., lower MIC) is used to evaluate the extent in activity change (numbers in boldface type in parentheses) after combination.

  • c The activity of EntXα+Xβ was enhanced compared with that of EntXα or EntXβ.

  • d The activity of EntXα+Xβ was reduced compared with that of EntXα or EntXβ.

  • e The activity of EntXα+Xβ was not significantly changed compared with that of EntXα or EntXβ.

  • f NA, no activity detected at the highest concentration of applied EntA (132,500 nM), EntB (89,000 nM), EntXα (6,500 nM), EntXβ (6,500 nM), or EntXα+Xβ (6,500 nM).