Antibacterial Properties of Non-Modified Wool, Determined and Discussed in Relation to ISO 20645:2004 Standard

Abstract

Wool is considered to possibly exhibit antibacterial properties due to the ability of wool clothing to reduce the build-up of odor, which arises from the microbial activity of skin microbiota. Indeed, when tested with a widely used agar diffusion plate test method, even wool or other textiles not treated with any antimicrobial agent can be interpreted to show certain antibacterial effects due to the lack of growth under the specimen, as instructed in ISO 20645:2004 standard. Therefore, we analyzed in detail what happens to bacterial cells in contact with untreated wool and cotton fabric placed on inoculated agar plates by counting viable cells attached to the specimens after 1 and 24 h of contact. All wool and several cotton samples showed no growth under the specimen. Nevertheless, it was shown without a doubt that neither textile material kills bacteria or inhibits cell multiplication. A reasonable explanation is that bacterial cells firmly attach to wool fibers forming a biofilm during multiplication. When the specimen was lifted off the nutrient agar surface, the cells in the form of biofilm remained attached to the wool fibers, removing the biomass and resulting in a clear, no growth zone underneath it. By imaging the textile specimens with X-ray microtomography, we concluded that the degree of attachment could be dependent on surface topography. The results indicate that certain textiles, in this case, wool, could exhibit antibacterial properties by removing excess bacteria that grow on the textile/skin interface when taken off the body.

Ag0–Ginger Nanocomposites Integrated into Natural Hydrogelated Matrices Used as Antimicrobial Delivery Systems Deposited on Cellulose Fabrics

“…For the evaluation of the antimicrobial activity, we used the "Agar diffusion plate test" method with coated fabric samples (2 × 2 cm 2 ) on the Sabouraud medium for fungi and Muller Hinton medium for bacteria, respectively, inoculated into the cloth with the tested microorganisms. Antimicrobial activity was evaluated according to ISO 20645:2004 [54] by measuring the diameter of the clear area (halo) that appeared around the textile specimens. The working inoculum was represented by a suspension made from a fresh culture in AFS (sterile physiological water), developed on a solid TSA (Tryptic Soy Agar) medium, with a density of 1.5 × 10 8 CFU/mL, nephelometrically adjusted (McFarland standard 0.5 = 1.5 × 10 8 CFU/mL).…”

“…Specimens from each cotton fabric finished with natural hydrogel loaded with the Ag 0 -ginger nanocomposite were evaluated regarding the antifungal and antibacterial activity by the "Agar diffusion plate test" (Table 3). According to the method presented in the literature [52,53] and in ISO 20645:2004 [54], each fabric sample was placed on a wet culture of microbial cells. The samples were moistened, and the silver ions diffused, reaching the culture of bacteria/fungi, where they affected their growth more or less in relation to the concentration of ions released from the multicomponent system.…”

Biochemical Behavior, Influence on Cell DNA Condition, and Microbiological Properties of Wool and Wool–Copper Materials

“…In spite of the great medical potential of both components of the WO-Cu material, only a few reports concerning the biochemical investigations of this combination of materials have been published [ 110 , 111 ].…”

“…Results of antimicrobial activity tests of WO-Cu(SpT) (MBC) materials. The wool fabric showed antibacterial efficacy towards SA if interpreted according to the agar diffusion test as "no growth" under the textile sample[111]. b/ Concentration of inoculum (CFU/mL): E. coli, 1.9 × 10 8 ; S. aureus, 1.9 × 10 8 ; C. globosum, 2.1 × 10 6 .…”