As can be seen, the viable population of the 0.1% (w/v) chitosan treated microorganisms was
less than that of the control throughout the incubation period (0-6 h) which indicated that chitosan could inhibit bacterial
growth at the tested concentration.However, chitin did not inhibit
the growth of both P. aeruginosa ATCC 27853 and P. melaninogenica.
In fact the curves overlapped with the controls (i.e. untreated cultures). This is in sharp contrast to the results observed with E.coli (Fig. 7), V. cholerae (Fig. 8), S. disenteriae (Fig. 9) and B. fragilis
(Fig. 10) where chitin and chitosan were equally effective as antimicrobial
agents. This suggests that the gram-negative strains P.aeruginosa ATCC 27853 and P. melaninogenica are more resistant to antimicrobial agents. Even chitosan was not as effective as shownby the slightly higher optical densities