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 shown
by the slightly higher optical densities (i.e. compare Figs. 11and 12
with Figs. 7e10). In a related study, Jeon et al. (2001) reported that
0.06% (w/v) chitosan more effectively inhibited E. coli than P. aeruginosa;
suggesting variable sensitivities of different microorganisms
to antimicrobial agents.