The Bacterial Life Cycle in Textiles is Governed by Fiber Hydrophobicity

Abstract

Colonization of textiles and subsequent metabolic degradation of sweat and sebum components by axillary skin bacteria cause the characteristic sweat malodor and discoloring of dirty clothes. Once inside the textile, the bacteria can form biofilms that are hard to remove by conventional washing. When the biofilm persists after washing, the textiles retain the sweat odor. To design biofilm removal and prevention strategies, the bacterial behavior needs to be understood in depth. Here, we aim to study the bacterial behavior in each of the four stages of the bacterial life cycle in textiles: adhesion, growth, drying, and washing. To accomplish this, we designed a novel in vitro model to mimic physiological sweating in cotton and polyester textiles, in which many of the parameters that influence bacterial behavior could be controlled. Due to the higher hydrophobicity, polyester adhered more bacteria and absorbed more sebum, the bacteria's primary nutrient source. Bacteria were therefore also more active in polyester textiles. However, polyester did not bind water as well as cotton. The increased water content of cotton allowed some species to retain a higher activity after the textile had dried. However, none of the textiles retained enough water upon drying to prevent the bacteria from adhering irreversibly to the textile fibers. This work demonstrates that bacterial colonization of textiles depends partially on the hydrophobic and hygroscopic properties of the textile material, indicating that it might be possible to direct bacterial behavior in a more favorable direction by modifying these surface properties. IMPORTANCE During sweating, bacteria from the skin enter the worn textile along with the sweat. Once inside the clothes, the bacteria produce sweat malodor and form colonies that are extremely hard to remove by washing. Over time, this leads to a decreasing textile quality and consumer comfort. To design prevention and removal mechanisms, we investigated the behavior of bacteria during the four stages of their life cycle in textiles: adhesion, growth, drying, and washing. The bacterial behavior in textiles during all four stages is found to be affected by the textile's ability to bind water and fat. The study indicates that sweat malodor and bacterial accumulation in textiles over time can be reduced by making the textiles more repellant to water and fat.

Keywords: biofilms; hydrophobicity; microbiology; skin; textile.

FIG 1

The life cycle of a bacterial biofilm on a textile fiber. The bacteria continuously undergo alternating and periodic stages of adhesion, growth, drying, and washing.

FIG 2

Physicochemical properties of cotton and polyester textiles. (a) Hydrophobicity of cotton and polyester textiles measured by the contact angle with water (n = 3). (b) Absorbed water content in cotton and polyester as measured by percentage of textile dry weight (n = 4). (c) Moisture regain of cotton and polyester after 24 h (n = 3). (d) Absorbed sweat (n = 6) and sebum (n = 10) in cotton and polyester textiles. (e) Evaporation of inoculated liquid from textile over time (n = 4). Statistical significance was evaluated by a two-tailed Welch t test.

FIG 3

Sebum distribution in cotton (a) and polyester (b) textiles. The top row shows CLSM images of the downfacing side of the textile, before and after drying, while the bottom row shows the upfacing side. The sebum is stained by Nile Red while the fibers autofluoresce in the blue region of the spectrum.

FIG 4

Bacterial adhesion to cotton and polyester textiles preinoculated either with sweat or with sweat and sebum. (a to e) Adhesion of five species to cotton and polyester. Adhesion is indicated by the number of bacteria left per cm³ of textile after washing with Triton X-100 (n = 3). (f) The surface densities of the single species were normalized and summarized to allow for comparison. Statistical significance was evaluated by a two-tailed Welch t test.

FIG 5

Bacterial activity in textiles. (a to f) ATP concentration was measured before and after 24 h of incubation (n = 3). (g) The ATP concentration is normalized and summarized to allow for comparison. Statistical significance was evaluated by a two-tailed Welch t test.

FIG 6

Bacterial adhesion to cotton and polyester before and after drying. The bacterial surface density, measured in μm³ bacterial volume per mm³ textile, is indicated before and after harsh washing (n = 8). Statistical significance was evaluated by a two-tailed Welch t test.

FIG 7

Capillary force acting on a bacterium in a thin water film. The capillary force, F_v, and the resulting potential energy, U, are shown as a function of the water film height for a range of water-bacterium contact angles, θ (°). Bacteria with different surface hydrophobicity experience different capillary forces, depending on the water film thickness. Thin water films tend to result in more attractive capillary forces. Adapted from reference .

FIG 8

Model designed to mimic textile in contact with sweating skin. The textile is brought in contact with the artificial sweat-sebum-microbiome inoculum for 1.5 h and incubated at 37°C for 24 h.