Antimicrobial textiles (65% cotton – 35% polyester) were functionalized using a patented technology that combines an antimicrobial molecule – polyhexamethylene biguanide (PHMB) and a precipitating agent – sodium laurylsulphate. Surface characterization was performed by x‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry, and both techniques made clear signatures of PHMB at the top surface of treated textiles. Washing led to a strong decrease of PHMB concentration at the surface. Comparison of textile surface analysis and antimicrobial tests indicated that the amount of PHMB at its extreme surface of textiles after five or 10 industrial washings was sufficient to inhibit Listeria innocua but not Pseudomonas aeruginosa growth. The viability of L. innocua cells after contact with PHMB‐treated textile after one industrial washing was estimated using the Live/Dead BacLight kit (Molecular Probes, Eugene, OR): the combination of epifluorescence microscopy observations coupled with classic enumeration allowed detection of the presence of viable but nonculturable cells.
PRACTICAL APPLICATIONS
Protective clothing is required in the food‐processing industry to protect products from being contaminated by microorganisms carried by workers' clothes or filtration systems. Consequently, there is an increasing interest in the use of antimicrobial functionalized textiles in the food industry to avoid that textiles could be vectors for pathogenic or food spoilage microorganisms. In the present study, the correlation between PHMB (the antimicrobial agent) at the surface of textiles (monitored by surface analysis characterization methods) and their antibacterial activity was assessed. After contact with antimicrobial textiles, the enumeration of bacteria was performed either by plate counting or by direct observation by epifluorescence microscopy in the presence of fluorescent viability markers in order to determine whether viable but nonculturable bacterial cells were present.
International audienceTextiles for the food processing industry are treated by a patented technology combining an ionic polymer (antimicrobial agent) and a precipitating agent to obtain an insoluble deposit expected to exhibit antimicrobial properties. ToF-SIMS and XPS are used in the understanding of the surface chemistry at various steps of treatments (cleaning step prior to surface modification, antimicrobial deposit, industrial ISO 15797 washing). ToF-SIMS and XPS analyses show that the signatures of the antimicrobial treatment are detected at the surface after treatment. After industrial ISO 15797 washings, the precipitating agent is rapidly removed (possibly replaced by washing agent components) while the antimicrobial agent (PHMB) is still detected but is significantly removed from the surface after five washings. ToF-SIMS and XPS data are compared to microbiological tests specifically intended in relation with food processing industry applications. After the antimicrobial treatment, the surface is biocide as well as after a single ISO 15797 washing, but after 5 washings, either the surface is slightly active (cotton-based textile) or not active any more (polyester-based textile). The XPS N atomic percentage variation is unable to explain this difference. Even though a slight difference is observed for the ToF-SIMS normalized intensity for m/z = 184.1561 (PHMB molecular peak) between C/P and P/C samples, it can hardly be concluded that this would be the only explanation for the difference in activity. ToF-SIMS indicates that cotton is the textile component still detected at the surface of the washed samples. This could play a role in the remaining efficiency of the antimicrobial treatment after industrial washin
Polyhexamethylene biguanide (PHMB) is a cationic biocide. The antibacterial mode of action of PHMB (at concentrations not exceeding its minimal inhibitory concentration) upon Listeria innocua LRGIA 01 was investigated by Fourier transformed infrared spectroscopy and fluorescence anisotropy analysis. Fourier transformed infrared spectra of bacteria treated with or without PHMB presented some differences in the lipids region: the CH(2)/CH(3) (2924 cm(-1)/2960 cm(-1)) band areas ratio significantly increased in the presence of PHMB. Since this ratio generally reflects membrane phospholipids and membrane microenvironment of the cells, these results suggest that PHMB molecules interact with membrane phospholipids and, thus, affect membrane fluidity and conformation. To assess the hypothesis of PHMB interaction with L. innocua membrane phospholipids and to clarify the PHMB mode of action, we performed fluorescence anisotropy experiments. Two probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and its derivative 1-[4-(trimethyl-amino)-phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), were used. DPH and TMA-DPH incorporate inside and at the surface of the cytoplasmic membrane, respectively. When PHMB was added, an increase of TMA-DPH fluorescence anisotropy was observed, but no changes of DPH fluorescence anisotropy occurred. These results are consistent with the hypothesis that PHMB molecules perturb L. innocua LRGIA 01 cytoplasmic membrane by interacting with the first layer of the membrane lipid bilayer.
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