Assesment of antimicrobial finishes on textile materials. AATCC 100: 2019.

Test accredited by ENAC (Spanish National Accreditation Entity)

            Antimicrobials are useful as additives in fabrics for several reasons: 1) because they provide protection against odors caused by the presence of microorganisms, without modifying the appearance or feel of the product, and 2) because when the fabrics are used in the area can help prevent infections in patients. For these reasons, fabrics with antimicrobial activity are demanded for sports and commercial garments, and for the medical area. In the medical area they can prevent infections by contaminating microorganisms of public interest such as methicillin-resistant Staphylococcus aureus (MRSA), among others. Whether the antimicrobial is incorporated into the fibers or applied to the surface of the tissue, it is necessary to prove its effectiveness. The AATCC 100 method is considered the standard method in the textile industry to quantify the antimicrobial activity of an antimicrobial fabric, since it allows to demonstrate if the fabrics or tissues inhibit the growth or kill the bacteria when they are exposed to them during a period of 24 hour contact. This method is carried out with bacteria grown in liquid medium, at a standardized concentration, which are inoculated into the cloths at an adequate dilution, so that they are put in contact with them, determining the concentration of the bacteria both at time zero, and at 24 hours, for which it is eluted in a neutralizing liquid so that the antimicrobial is neutralized and allows the growth of viable bacteria if they are present. The method is carried out in parallel with pieces of control fabrics without antimicrobials that allow comparatively demonstrate the effect obtained with the fabric containing the antimicrobial, and thus be able to determine the concentration of bacteria and its reduction, if any. In order to demonstrate this, the reduction in the number of bacteria after the contact period with respect to the initial concentrations should be calculated both in the antimicrobial fabrics and in the respective controls without antimicrobials. This method is quantitative and reproducible, and can determine both bacteriostatic antimicrobial activity, which inhibits the growth of bacteria, and bactericidal antimicrobial activity, which kills bacteria. This method is carried out in the presence of the nutrients and growth conditions suitable for the multiplication of the bacteria used, so that the inhibition of their growth or death, only occurs if the fabrics are sufficiently antimicrobial. In order to perform the method properly, the fabrics must absorb liquids, that is, they must not be hydrophobic. The test is performed with pieces of circular cloth of 4.8 cm in diameter, with antimicrobial and without antimicrobial (controls), with or without prior sterilization, with or without prior washing, as recommended by the manufacturer, using two species of bacteria (Klebsiella pneumoniae and Staphylococcus aureus). The contact between the bacteria and the fabrics is kept in incubation for 18 to 24 hours at 37°C, and then the bacteria are eluted with a neutralizing solution for quantification, the percentage of reduction being calculated. Additional methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, vancomycin-resistant Enterococcus, Salmonella spp. or any other chosen by the client. For the realization the client must provide the pieces of cloth of 4.8 cm in diameter, both with antimicrobials, and without them, in sufficient number to carry out the process in duplicate and with the two bacteria (minimum 32 pieces with antimicrobials and 16 pieces without antimicrobial).