The following bacterial strains were obtained from the
Univeristy of Santo Tomas Collection of Microbial Culture
(USTCMS): Gram-negative bacteria [Escherichia coli ATCC
25922 (E. coli), Escherichia hormaechei ATCC 700323,
Klebsiella oxytoca ATCC 7003224, Klebsiella pneumonia
USTCMS 1040 (K. pneumonia) and Pseudomonas aeruginosa
ATCC 27853 (P. aeruginosa)] and Gram-positive bacteria
[Staphylococcus aureus ATCC 25923 and ATCC 29213 (S.
aureus), Staphylococcus sciuri ATCC 29061, Staphylococcus
epidermidis ATCC 12228 and Bacillus subtilis USTCMS 1011 (B.
subtilis)]. The bacterial cultures were maintained on MHA
slant at 4 °C, and were subcultured on fresh agar plate for 24
h before the antibacterial assay