newsletter - Point of Shoes kommt gut an

INFORMATION
Bacteria are divided into two large
groups according to the structure
of their cell wall: Gram-positive and
Gram-negative bacteria. The groups
are distinguished by Gram staining
based on the different chemical and
physical properties of the cell walls.
The diagnostic method, and hence
the assignment of bacteria to the
different groups, is named after the
Danish bacteriologist H. Ch. Gram.
Staphylococcus aureus is an immobile,
spherical Gram-positive
bacterium, often appearing as grapelike
clusters. This microorganism is of
widespread occurrence. It forms part
of the normal skin fl ora but on entering
the body and in cases of weak
immune systems it can cause infections
which may be life-threatening.
Escherichia coli is a rod-shaped,
Gram-negative bacterium occurring
in the intestines of humans and animals.
It is one of best-studied organisms
known. It serves as an indicator
of faecal contamination and of poor
hygiene. Some E. coli strains may be
pathogenic and cause infections or
poisoning.
Antibacterial activity is proved if
independent tests show inhibition of
bacterial growth or death of bacterial
cells, both for a Gram-positive
and for a Gram-negative test microorganism.
NEWSLETTER
Extended Range of Antimicrobial Effi cacy Tests Offered by PFI
Accreditation of New Test for Determining the
Antibacterial Activity of Plastics Surfaces
In the course of the successful re-accreditation of the Department of
Microbiology and Molecular Biology at PFI, the contact fi lm method according
to ISO 22196 has been included in the range of test methods offered.
This represents further extension of one of the core competences
of the microbiology laboratory. Those involved in development, fi nishing,
and quality testing as well as retailers benefi t from a comprehensive
range of accredited procedures in the area of antimicrobial effi cacy
testing.
Greater demands on hygiene are contributing to increasingly widespread application
of materials with antibacterial fi nishes. Plastics with such fi nishes are
used in many fi elds, especially in the medical fi eld, in the food sector, in surface
design and development, and most recently also in the footwear industry.
The international standard ISO 22196, originally based on the Japanese Industrial
Standard JIS Z 2801, describes the determination of the antibacterial
activity of appropriately treated plastic surfaces. The test is performed under
static conditions, in contrast to the less practical dynamic conditions of other
procedures. A bacterial suspension
with a defi ned number of cells of a
given test organism is applied to the
test object and to an untreated reference
material and covered with a
fi lm. The fi lm ensures good contact
of the suspension with the smooth
test surface over the entire duration
of the test and also provides protec-
Application of the bacterial suspention
against evaporation of liquid.
sion to a specimen
The number of living cells on the
Aufbringen der Bakteriensuspension
test object and that on the reference
auf einen Prüfl ing
material are determined immediately
after application of the bacteria and after incubation for 24 hours and the antibacterial
activity is calculated. Staphylococcus aureus and Escherichia coli serve
as test microorganisms (bacteria).