The present study examined the effects of antimicrobial agents on a biofilm
model of Staphylococcus aureus. A membranous structure (an immature biofil
m) was formed on the coverslips of tissue culture dishes by S. aureus cells
in plasma after incubation for 24 h, After incubation, the colony counts o
f S. aureus cells in the immature biofilms in plasma containing levofloxaci
n with 70% sucrose were about one-tenth of those in plasma containing levof
loxacin without sucrose. The colony counts of S. aureus cells in the immatu
re biofilms in plasma containing silver sulphadiazine or silver nitrate (at
a silver concentration of 0.302%) were over 3000 times lower than those in
control plasma without silver after incubation for 24 h. Plasma coagulatio
n by S. aureus cells was not detected in plasma containing 70% sucrose 48 h
after inoculation. The immature biofilms were incubated in plasma with and
without 70% sucrose, and the immature biofilms were treated with 10% povid
one-iodine for 2 min after incubation for 4 and 16 h. In this experiment, t
he colony counts of S. aureus cells in the immature biofilms incubated with
70% sucrose were about one-tenth of those in plasma without sucrose after
incubation for 24 h. We suggest that levofloxacin or 10% povidone-iodine in
combination with 70% sucrose and silver sulphadiazine or silver nitrate (a
t a silver concentration of 0.302%) are effective in eliminating S. aureus
cells in a biofilm.