Almost all V. cholerae and B. fragilis were destroyed after 1.5 h and 2 h of incubation, respectively, in the presence of 0.1% (w/v) chito-oligomers in the culture medium. Although, the required time for killing all S. disenteriae was 1.5 h and 2.5 h for COS and NAc-COS respectively, suggesting that COS is a more effective antimicrobial agent.