20 Bacterial Adherence on Fabrics by a Radioisotope Labeling Method YOU-LO HSIEH, 1 DEBRA A. TIMM, AND JOANNE MERRY Division of Textiles and Clothing, University of California at Davis, Davis, California 95616, U.S.A. ABSTRACT A radioisotope labeling technique was used to quantify the adherence of Staphy- lococcus aureus, Staphylococcus epidermidis, and Escherichia coli on eight fabrics. The extent of bacterial adherence depends on the bacterial type, the fiber content, and the contact condition. Staphylococci adhered more than Escherichia coli, and Staph. epidermidis adhered more than Staph. aureus on all fabrics. There were apparently different degrees of bacterial adherence in the eight fabrics, but the ranking orders of adherence depended to a great extent on the contact condition. Bacterial adherence was increased by both agitation and saturated wetting due to increasing bacterial cell- fiber contact. There was an increasing trend in bacterial adherence on all fabrics as contact time increased up to 24 hours, with occasional zig-zag patterns. On most fabrics, cleaning and autoclaving did significantly influence the extent of bacterial adherence to the fabrics. The quantitative data along with the morphology of bacterial adherence by SEM suggested that factors other than hydrophilicity, water absorbency, and surface roughness may affect the extent of bacterial adherence to the fibers. Bacteria adhere tenaciously to solid surfaces ranging from biological tissues and cells in animals and plants to inert materials such as metals and polymers. Bac- - terial adherence can be of economic importance in fouling of marine equipment [3] and biomedical im- portance in reducing pathogenesis caused by bacterial adherence on prosthetic implants [2, 4] and surgical/ hospital supplies. The use of fibrous materials in con- sumer, biomedical, and industrial applications has been very extensive. Little research, however, has been done to understand the intrinsic adherent behavior of bac- terial cells to unfinished fibrous materials. In our previous study, we analyzed bacterial adher- ence on cotton, polyester, and their blends under a static suspension contact condition [5]. Staphylococci adhered to those fabrics much more than did Esche- richia coli. In addition, the adherence of staphylococci increased as the content of polyester fiber in the fabrics increased. Escherichia coli, on the other hand, showed no preference for adhering to any of those fabrics. We also found that the extent of bacterial adherence under static suspension was independent of the concentration of the bacterial suspension. Since knowledge of bacterial adherence to fibers is very important in better selection and modification of fibers in some end-use applications, this study extended the evaluation of bacterial adherence to include eight common natural and synthetic fibers. Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli were selected because they are the major human skin flora [ 1, 7, 11 ] and the most common pathogens for wound infections [9, 10]. The latter two organisms have also been identifed to produce body odor from perspiration [8]. The effects of different contamination methods, contact time, and cleaning and autoclaving on bacterial adherence to these fibers were investigated. Procedure BACTERIA The gram-positive staphylococci used in this study were Staphylococcus aureus (Staph. aureus) and Staphylococcus epidermidis (Staph. epidermidis). Both strains were isolated and cultured from hospital pa- tients. The gram-negative Escherichia coli (E. coli) was American Type Culture Collection (ATCC) # 1346. All bacteria suspensions used in this study were freshly prepared for each experiment. FABRIC PREPARATION The eight fabrics of natural and synthetic origins used in this study were cotton, rayon, acetate, wool, nylon, Orlon, polyester, and polypropylene (Test Fab- rics, Inc.). They were characterized by fabric count (ASTM 1910), weight (ASTM 1910), and moisture re- gain (AATCC 20A). Fabrics were cut into circular pieces 1.9cm in diameter with a die. The area of a ’ To whom all correspondence should be addressed. at UNIV CALIFORNIA DAVIS on June 11, 2015 trj.sagepub.com Downloaded from