Lethal effect of chitosan‐Ag (I) films on Staphylococcus aureus as evaluated by electron microscopy

Aim: 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. Methods and 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. Significance and Impact of the Study: Information from this study can be employed in guiding future strategies to improve the design of materials for the food industry packaging.