Enterococcus faecalis

Bacterial strains and culture conditionThe bacterial strains (Microbiologics, Inc., St. Cloud, Minnesota, USA) used were Escherichia coli ATCC^Ⓡ 25,922™, Proteus mirabilis ATCC^Ⓡ 25,933™, Staphylococcus aureus subspecies aureus ATCC^Ⓡ 25,923™, Staphylococcus epidermidis ATCC^Ⓡ 12,228™ and Enterococcus faecalis ATCC^Ⓡ 29,212™.
About 50µL of bacterial frozen stocks samples (10⁸ CFU/ml) were inoculated in BHI (brain heart infusion) and incubated at 37 °C for 24 h.

Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Enterococcus faecalis ATCC 29212, Streptococcus pneumonia ATCC 49619 and Acinetobacter baumanii ATCC 19606 were obtained from Microbiologics (St. Cloud, MN). E. faecalis ATCC 51575, ATCC 51299 and REMEL C99707 and E. faecium ATCC 51559 (MDR), REMEL IH79985 and REMEL C110914 were generously provided by the Laboratory of Pathology, University of Maryland Baltimore School of Medicine. Unless stated otherwise, chemicals and reagents were purchased from Sigma.

Gram-negative strains Escherichia coli (ATCC 25922), Enterobacter aerogenes (ATCC 13048) and Pseudomonas aeruginosa (ATCC 27853), Gram-positive strains Staphylococcus aureus (ATCC 25923) and Enterococcus faecalis (ATCC 29212), and fungal strain Candida albicans (ATCC 90028) were obtained from Microbiologics Inc., and used for the antimicrobial screening. Strains were selected according to the guidelines set for clinical laboratories by Clinical and Laboratory Standards Institute [CLSI, formerly National Committee on Clinical Laboratory Standards [22] ] and the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Bacterial strains were grown on Mueller Hinton II Agar (MHA) (BBL, BD) and Mueller Hinton II broth (MHB) (BBL, BD), whereas Candida was initiated on Sabouraud Dextrose Agar (SDA) (Difco, BD) plates. Media were prepared into MilliQ water according to manufacturer’s instruction and autoclaved at 121°C for 15 min. Bacteria were plated on MHA plates and incubated at 37°C for 16–18 h. Bacterial suspension for the assays was prepared by subculturing the bacteria into MHB and by incubating at 37°C for 16–20 h at 110 rpm prior to the assay. Candida strain was grown on SDA plates at 27°C for 16–18 h and suspended into sterile 0.9% saline for the assay.