Time-Kill Tests

Standard Time-Kill test (ASTM E2315)

A Standard Time-Kill (STK) is a laboratory test which measures the antimicrobial performance of a liquid sample over a short period of time. The kill test quantifies the reduction in numbers of a known inoculum of microorganisms over specified contact times. This method determines the effective kill rate of a finished product, usually expressed as a % (for example, “kills 99.9% of bacteria in 30 seconds”).

Time-Kill Test (Liquid product)

Regular price £50.00

Time-Kill Test (Solid product)

Regular price £85.00

Time-Kill Tests

The Time-Kill test measures changes in a population of aerobic microorganisms within a specified sampling time when antimicrobial test materials are present.

The STK test gives a result such as “kills 99.9% of bacteria in 30 seconds”.

Suitability of test

The Standard Time-Kill test can be performed on any liquid finished product, for example, hand sanitisers, disinfectant cleaning products, anti-bacterial liquid soaps, mouthwash, and so on.

The effective kill rate can be determined for any type of microorganism, though most commonly bacterial species such as Pseudomonas aeruginosa are used.

The contact time chosen for the STK should be appropriate for the type of finished product under test. For example, a hand sanitiser may be tested with a contact time of 30 seconds, whereas a hard surface cleaner can be tested over a longer period of time, depending on its instructions for use.

Test Details

The testing will require a 250 g sample of your liquid product.

The sample is inoculated with a known amount of microbes.

At set intervals (for example, 30 s, 1 min, 2 min, 3 min, 5 min) an aliquot is removed from the sample and placed into a biostatic diluent to deactivate the biocides present in the sample.

The diluent is then placed onto special growth medium and incubated, so that the number of surviving microbes can be counted.

	ASTM E2315
Exposure times	30s, 1m, 2m, 3m, 5m
Sample required (g)	250
Total Species	4/5
Staphylococcus aureus	●
Pseudomonas aeruginosa	●
Enterococcus hirae	●
Escherichia coli	●
Candida albicans	○

Test Species

As standard, the STK is performed with a mixture of 4 test species of microorganism.

For specific end products, we can also test against appropriate organisms, for example, feminine wash products may be tested against Candida albicans.

If you require a specific test culture or contact time that is not listed, then please contact us to arrange a customised method.

Time-Kill Tests

Time-Kill Tests

Suitability of test

Test Details

● Standard○ Optional (feminine products)

Test Species

● Standard
○ Optional (feminine products)