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Strains of the samples below from the laboratory culture collection were incubated overnight in Tryptone Soy Broth (oxoid). 0.1ml of each strain was added to 10ml of Tryptone Soy Broth containing 0.5% Tween 80 as a dispersant. 0.2ml of the resulting 1:100 dilution was spread over each of the two 50cm2 areas of samples 1 and sample 2 respectively.

A 10cm2 area of each panel was sampled by standard swabbing with a damp cotton tip swab using a template to define the area at 2 minutes, 3 hours and 6 hours.

The swabs were squeezed out into 10ml of Tryptone Soy Broth with Tween 80 and vortexed for 30 seconds to elute the organisms from the cotton tip.

0.1ml of each vortexed broth was inoculated and spread onto culture media selective for each separate strain in a attempt to recover them. All culture media used were supplied by Oxoid. The strains were recognised after appropriate incubation by the following criteria.

Sample 1

SAMPLE CFU @ 2MIN CFU @ 3 HOURS CFU @ 6 HOURS
MRSA 55 70 61
Staphylococcus Aureus 98 108 6
Eschericia coli 64 151 16
Eschericia coli 0157 52 90 1
Listeria monocytogenes 23 29 0
Salmonella Poona 73 153 5
Sample 2
SAMPLE CFU @ 2MIN CFU @ 3 HOURS CFU @ 6 HOURS
MRSA 296 0 0
Staphylococcus Aureus 270 14 0
Eschericia coli 257 30 0
Eschericia coli 0157 222 17 0
Listeria monocytogenes 229 12 0
Salmonella Poona 200 48 0

Conclusion

Comparison of the results from Sample 1 and Sample 2 shows that Sample 1 shows no diminution of recovery at 3 hours as compared to 2 minutes, and even the possibility of a slight increase in numbers recovered at 3 hours. Sample 2, meanwhile shows a marked reduction in organisms recovered, and that from an apparently higher inoculum.

At 6 hours there is no recovery or organisms from Sample 2, whilst Sample 1 still shows some recovery of those strains that have resisted dessication.

Sample 2, which contains the biocide, is superior in the elimination of organisms from the panel.
© 2008 Morgan Polymers Ltd