Comparison of adhesion of the food spoilage bacterium Shewanella putrefaciens to stainless steel and silver surfaces.
OBJECTIVE
To compare the number of attached Shewanella putrefaciens on stainless steel with different silver surfaces, thus evaluating whether silver surfaces could contribute to a higher hygienic status in the food industry.


RESULTS
Bacterial adhesion to three types of silver surface (new silver, tarnished silver and sulphide-treated silver) was compared with adhesion to stainless steel (AISI 316) using the Malthus indirect conductance method to estimate the number of cfu cm(-2). The number of attached bacteria on new silver surfaces was lower than on steel for samples taken after 24 h. However, this was not statistically significant (P > 0.05). The numbers of attached bacteria were consistently lower when tarnished silver surfaces were compared with stainless steel and some, but not all, experiments showed statistical significance (P < 0.05). Treating new silver with sulphide to reproduce a tarnished silver surface did not result in a similar lowering of adhering cells when compared with steel (P > 0.05).


CONCLUSIONS
New or tarnished silver surfaces caused a slight reduction in numbers of attached bacteria; however, the difference was only sometimes statistically significant.


CONCLUSIONS
The lack of reproducibility in differences in numbers adhering to the different surfaces and lack of statistical significance between numbers of adhered viable bacteria do not indicate that the tested silver surfaces can be used to improve hygienic characteristics of surfaces in the food industry.
Hjelm
M
M
Department of Manufacturing Engineering and Management, Technical University of Denmark. meh@dfu.min.dk
Hilbert
L R
LR
Møller
P
P
Gram
L
L
D001422:Bacterial Adhesion; D015169:Colony Count, Microbial; D003470:Culture Media; D005506:Food Contamination; D019649:Food Industry; D008855:Microscopy, Electron, Scanning; D020614:Shewanella putrefaciens / Q000502:physiology*; D012834:Silver; D013193:Stainless Steel
D003470:Culture Media; D013193:Stainless Steel; D012834:Silver