Test accredited by ENAC (Spanish National Accreditation Entity).
The ASTM E2783 standard describes a test procedure to determine the existence of antimicrobial activity of compounds miscible in water by means of a time-kill procedure.
To perform the test, an aliquot of the test formulation, or a dilution of the test formulation in water, is contacted with a known inoculum in triplicate. In parallel, the test is performed with a water control. The standard allows the test to be carried out with a volume of test product of 10 or 100 mL. In our laboratory, the test will be carried out with a volume of 10 mL, provided that the client does not specify otherwise. As test inoculum, the standard includes the following list of microorganisms: Acinetobacter spp., Candida albicans, Enterobacter spp., Enterococcus faecalis, Enterococcus faecium, Escherichia coli, Klebsiella pneumoniae, Micrococcus luteus, Pseudomonas aeruginosa, Proteus mirabilis, Salmonella enterica, Serratia marcescens, Shigella spp., Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus saprophyticus, Streptococcus pyogenes, and Streptococcus pneumoniae. Following inoculation with the test microorganism, the samples are incubated for specified periods of time and at a specified temperature. Test times should reflect the intended use of the material (any range covering several minutes or hours) and may be chosen to construct a kinetic kill model. The test temperature will be room temperature, from 18ºC to 25ºC, unless the test formulation requires another temperature (for example, solid products at room temperature or products only stable at another temperature). After each test time, the test material is neutralized, and the number of viable microorganisms is determined for each concentration and test microorganism. Subsequently, the reduction percentage and the logarithmic reduction obtained are calculated, comparing the counts obtained with the test formulation and water control formulation with water. The ASTM E2783 standard does not indicate a criterion to conclude whether the product shows antimicrobial activity. The primary purpose of this test method is to provide a set of standardized conditions and test organisms to facilitate comparative assessments of antimicrobial materials miscible in aqueous systems.