It was found in the present study that combined use of fusidic acid (FA) and 
berberine chloride (BBR) offered an in vitro synergistic action against 7 of the 
30 clinical methicillin-resistant Staphylococcus aureus (MRSA) strains, with a 
fractional inhibitory concentration (FIC) index ranging from 0.5 to 0.19. This 
synergistic effect was most pronounced on MRSA 4806, an FA-resistant isolate, 
with a minimum inhibitory concentration (MIC) value of 1,024 μg/ml. The 
time-kill curve experiment showed that FA plus BBR yielded a 4.2 log10 c.f.u./ml 
reduction in the number of MRSA 4806 bacteria after 24-h incubation as compared 
with BBR alone. Viable count analysis showed that FA plus BBR produced a 3.0 
log10 c.f.u./ml decrease in biofilm formation and a 1.5 log10 c.f.u./ml decrease 
in mature biofilm in viable cell density as compared with BBR alone. In 
addition, phase contrast micrographs confirmed that biofilm formation was 
significantly inhibited and mature biofilm was obviously destructed when FA was 
used in combination with BBR. These results provide evidence that combined use 
of FA and BBR may prove to be a promising clinical therapeutic strategy against 
MRSA.