In vitro antimicrobial activity of chitosan-silver and chitosan-gentamicin membranes on Staphylococcus aureus and Escherichia coli.

The aim of this work was the development of chitosan based membranes and to examine its antimicrobial activity in vitro against Staphylococcus aureus and Escherichia coli. Chitosan porous membranes (CS) loaded with proper amount of silver nanoparticles (CS/AgNP) or gentamicin sulphate (CS/GM) were fabricated. The antibacterial effect was compared by viable cell colony count method (CFU/ml). Briefly, a culture of each microorganism, with an optical density of 0.2 at 600nm (105 CFU/ml) was inoculated in tubes with MHB. CS based membranes containing antibacterial agents were added to tubes for 18 h at 37°C. A chitosan membrane without silver and gentamicin was used as control. Serial dilutions were made and plated in Petri dishes with TSA and after an incubation of 18 h colonies were counted. CS/GM loaded samples showed total bactericidal efficacy towards both S. aureus and E. coli due to the bacteria susceptibility to gentamicin sulphate. CS/AgNP10% loaded samples showed a less antimicrobial activity compared to antibiotic loaded ones, but however higher than controls (CS). CS/AgNP10% membranes displaced more efficiency inhibitory against Gram positive strain (S. aureus) than Gram negative (E. coli), this is probably due to the fact that Gram negative cell wall has a thick peptidoglycan layer with a great capacity to protect the cell from the penetration of silver ions and small nanoparticles into the cytoplasm. The results obtained from the study in vitro suggested that membranes with silver and specially gentamicin could be tested in vivo.