MICs were determined as the lowest concentrations of chitosan or COS at which microorganisms cannot grow in Muller-Hinton broth ; based on the method of R., the strains were inoculated into M-H broth and incubated to the longarithmic growth phase at 37 C. The growth density was adjusted to match a MacFarland 0.5 standard (10 8 CFU/ml). A 1:100 dilution was prepared in a fresh M-H broth, and used as the inoculum (10 6 CFU/ml); several concentrations were tested, and microbial growth was monitored via turbidity by 24 h of incubation at 37 C.