Bacterial inhibition
Bacterial inhibition, biofilm, Nosocomial infection, Cu, Ag ions
The term bacterial inhibition refers to the ability of a surface to actively suppress the occurrence and reproduction of microbial organisms . Specialized layers containing silver or copper can be used for such inhibition.
The spread of nosocomial infections, such as Staphylococcus aureus (Golden Staphylococcus), Escherichia coli and others that have become largely resistant to commonly used alcohol-based disinfectants and may also be resistant to antibiotic treatment. These organisms then form a biofilm and when this comes into contact with a disinfectant the bacteria in its upper layers are eliminated while the lower bacterial layers remain unaffected. Despite compliance with strict hygiene standards, these bacteria remain present on surfaces and can cause serious infections. The function of bacterially inhibiting surface layers has thus grown greatly in importance.
Description
The principle of bacterial inhibition in selected PVD coatings lies in the possible combination of two effects. The prevention of attachment of bacteria on a given surface (passive) and a release of active metal ions, especially copper and silver, from the coating to the environment on its surface (active). When these ions come into contact with a bacterial cell, they cause damage to its cell wall and subsequently damage the structure of its DNA. As a result, the bacterium loses its ability to multiply and subsequently dies.
Measurement
The measurement can be carried out, for example, according to the standard ČSN 11737-1 – Sterilization of health care products, Microbiological methods. Or according to the JIS Z2801:2000 standard – Test for Antimicrobial Activity of Plastics. Or according to other standards required by the specified application.
At SHM, we have experience with several types of bacterial actives, PVD layers containing copper and silver in which a high degree of bacterial inhibition has been demonstrated in the laboratory against a wide range of bacterial colonies including E.Coli, P. aeruginosa, S. aureus, S. epidermidis and the bacteria commonly present on the surface of a person’s palm. In the picture below you can see the results of the antimicrobial tests. In the Petri dishes on the left there are control samples of bacterial colonies grown under the same conditions without the presence of an antibacterial coating. In the dishes on the right we see the environment of the sample when presented with an antibacterial PVD coating.
