N-Carboxybutyl chitosan, a modified chitin of crustacean origin, displayed inhibitory, bactericidal, and candidacidal activities when tested against 298 cultures of various pathogens. Examination by electron microscopy showed that microbial cells exposed to N-carboxybutyl chitosan underwent marked morphological alterations. The data are of importance in defining the suitability of N-carboxybutyl chitosan as a wound dressing.A number of polysaccharides, mainly cross-linked dextran, calcium alginate, carboxymethyl starch, modified agar, and carboxymethyl cellulose, are used in wound treatment (13,17). These polysaccharides, however, do not seem to combine favorable physical forms with functional properties; rather, besides the hemostatic action of oxycellulose, no functional property has been reported (17). The same is true for gelatin and collagen (15). On the other hand, chitin derivatives are not in widespread use as wound dressings, and relevant studies on wound healing have been confined to a few recent articles (1, 11). Interestingly, some antibacterial and antifungal activities have been described with chitosan and modified chitosans (5,8,9,18).N-Carboxybutyl chitosan is more versatile than any other polysaccharide currently used in wound management and lends itself to the manufacture of wound dressings with peculiar characteristics. Such dressings, in particular, can stimulate ordered regeneration (3) and vascularization (10) of tissue and allow gaseous exchange and turn into a gel form when they are in contact with body fluids (14), thus permitting dressing removal without disturbing the newly formed tissues. We undertook the present study to define the antimicrobial properties of N-carboxybutyl chitosan and to test it in different physical forms in view of its use in wound management. N-Carboxybutyl chitosan, which was prepared from crustacean chitosan (degree of deacetylation, 0.73) according to a proprietary procedure (R. Muzzarelli, U.S. patent 4,835,265, June 1986) and as described previously (12, 14), was tested against a variety of gram-positive and gramnegative pathogens and Candida spp. A total of 298 strains were used, all of which were freshly isolated from clinical material and identified according to conventional laboratory criteria.Two different methods were used to assess the antimicrobial activity of N-carboxybutyl chitosan. The first method was a quantitative assay based on conventional agar dilution tests (20), with final concentrations being 2, 4, 6, 8, and 9 mg/ml (concentrations above 9 mg/ml did not permit full solubilization of N-carboxybutyl chitosan into the test medium). The inoculum suspensions were prepared from fresh broth cultures and adjusted to obtain a concentration of approximately 107 CFU/ml. Test plates were inoculated by using an automatic replicating device (Titertek; Flow Labo-* Corresponding author. ratories, Inc., McLean, Va.) that delivered 1 1.l of bacterial suspension per spot. A control plate with no N-carboxybutyl chitosan was inoculated first, and a second co...
