Lethal effect of chitosan-Ag (I) films on Staphylococcus aureus as evaluated by electron microscopy.
OBJECTIVE
This article investigated the lethal effect and morphological changes on Staphylococcus aureus strains ATCC 25923 and ATCC 6538P produced by chitosan-Ag (I) films as observed by electron microscopy.


RESULTS
The antimicrobial activity of films against staphylococci was determined using the broth dilution method and agar diffusion test. Killing curves, transmission and scanning electron microscopy (TEM and SEM) techniques were employed to evaluate the bacterial death and morphological changes in bacterial cells after exposure to chitosan-Ag (I) films. Films affected the cell structure of Staph. aureus, causing elongation of cells, disaggregation of grape-like cluster, contraction of bacterial cytoplasm, thickening of cell wall, increase in cell wall roughness, cell disruption with loss of intracellular material, filamentation and bacteriolysis, as seen in the micrographs following 3, 6, 12 and 16 h of incubation.


CONCLUSIONS
Obtained images clearly show that chitosan-Ag (I) films have a notable antistaphylococcal activity.


CONCLUSIONS
Information from this study can be employed in guiding future strategies to improve the design of materials for the food industry packaging.
Díaz-Visurraga
J
J
CIPA-Chile, Faculty of Chemistry Sciences, Department of Polymers, Advanced Materials Laboratory, University of Concepcion, Concepcion, Chile.
García
A
A
Cárdenas
G
G
D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D001433:Bacteriolysis; D002473:Cell Wall / Q000648:ultrastructure; D048271:Chitosan / Q000737:chemistry / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008854:Microscopy, Electron; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000648:ultrastructure
D000890:Anti-Infective Agents; D012834:Silver; D048271:Chitosan