Catheter related bacteremia in rats: A preliminary report on the effect of methylene blue coated catheter

The safety and efficacy of methylene blue (MB) coated indwelling jugular vein/cranial vena cava catheter made up of polyurethane material was tested in a rat model, receiving bacterial culture suspension of Pseudomonas aeruginosa, and Staphylococcus aureus. Daily blood samples were collected from the catheter and peripheral vein for bacterial culture. The clinical parameters (rectal temperature, respiratory rate, total white blood cell count, and loss in body weight) were not different between the groups. All the rats became bacteremic with similar changes in the number of colony forming units in the catheter and peripheral samples. Histopathological lesions were not different between the groups. The findings suggest that rats receiving MB coated catheters behaved similar to non-coated catheters. Based on the results it can be concluded that for this type of gross contamination, catheter coating alone may not eliminate infection/bacteremia.     

家蝇抗菌肽的抑菌动力学研究及其机理初探

利用鼠伤寒沙门氏菌针刺诱导家蝇幼虫表达抗菌肽,对抗菌肽的抑菌动力学进行研究,并通过抗菌肽样品对不同细菌动力学特性的研究出发对抗菌肽抑菌作用机制进行探讨。研究发现抗菌肽样品的活性与作用时间有关,24h内出现一到两个活性峰,同一抗菌肽样品对不同细菌的抑菌动力学有差异,抗菌肽的抑菌动力学机制应该与它的的抑菌作用机制有关。通过电镜观测、细胞磷代谢、紫外吸收物测定以及抗菌肽与细菌DNA相互作用结果可知,微生物诱导家蝇表达的抗菌肽样品不仅能够造成细菌细胞的快速坍塌破裂而且能够破坏细胞核心,与DNA结合作用。抗菌肽抑菌动力学的解释：微生物诱导产物中含有两类抗菌肽,一类抗菌肽能造成细胞膜的快速坍塌破裂形成第一个活性峰;另一类抗菌肽可进入细胞,破坏细胞核心,造成紫外吸收物大量外泄形成第二个活性峰。     

Protection of catheter surfaces from adhesion of Pseudomonas aeruginosa by a combination of silver ions and lectins

A catheter surface was modified by coating a cellulose acetate polymer. Adhesion of Pseudomonas aeruginosa ATCC 27853 to the surface was investigated by exposing bacterial cultures to three treatments: polymer impregnated with silver ions (Ag⁺), polymer surfaces coated with lectins and a combination of Ag⁺ and a lectin coating. The effective concentration of Ag⁺ providing protection against bacterial biofilm development was 100g/ml and higher. Lectins alone at 10% also showed inhibition of bacterial attachment. However, the best result was achieved against bacterial adhesion and growth on surfaces using a combination of 100 g Ag⁺/ml and a lectin coating as a surface treatment. This surface treatment was also effective against both fresh culture and a two-week-old culture containing P. aeruginosa producing exopolymers. Our results suggest that Ag⁺impregnation combined with a lectin coating warrants further investigation as a potential means of protecting catheters.     

Influence of lactoferrin feeding and injection against systemic staphylococcal infections in mice

Human and bovine lactoferrins (Lfs) and bovine lactoferrin hydrolysate (LH) were assessed in vitro and in vivo for their antibacterial effects on Staphylococcus aureus. Lactoferrins showed weak in vitro antibacterial activity while Fe-saturated Lfs and LH showed no activity. Lactoferrin-treated mice (1 mg, i.v.) when injected i.v. with 10(6) staphylococci, showed 30-50% reduction in kidney infections, and viable bacterial counts in the kidneys decreased 5-12-fold. The inhibitory effect was dose-dependent up to 1 mg Lf. Lactoferrins were effective when given 1 day prior to the bacterial challenge, after which there was no significant effect even at doses up to 5 mg. Apo- and Fe-saturated forms of human and bovine Lfs were all equally effective, while LH was not protective. Human and bovine Lfs with different degrees of iron saturation (9-97%) were found to be equipotent. Feeding mice with 2% bLf in drinking water also reduced the kidney infections by 40-60%, and viable bacterial counts, 5-12-fold. The results suggest a potential for the use of Lfs as natural antibacterial proteins for preventing bacterial infections.     

Antibacterial activity of pyrrolidine dithiocarbamate

Pyrrolidine dithiocarbamate (PDTC), an antioxidant with a metal-chelating activity, has been used widely to inhibit the expression of inflammatory genes in vitro and in vivo. This study investigated whether PDTC has an antimicrobial activity against various bacteria. The antibacterial activity of PDTC and other compounds was evaluated in vitro by the broth microdilution method against Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Staphylococcus aureus, and Escherichia coli. Bacterial growth was inhibited by PDTC, where a wide range of sensitivity was demonstrated among the tested bacteria. The antibacterial activity of PDTC was reduced by the addition of copper chloride; in contrast, it was enhanced considerably by zinc chloride. Two different zinc chelators, Ca-saturated EDTA (Ca-EDTA) and N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine, blocked the antibacterial activity of PDTC, whereas Zn-EDTA failed to reduce the activity of PDTC. These results demonstrate for the first time that PDTC possesses an antibacterial activity, for which zinc is required, and suggest that PDTC, possessing a dual anti-inflammatory and antibacterial activity, may be considered for topical use for inflammatory diseases of bacterial origin.     

载银纳米抗菌复合骨填充材料体外抗菌性能研究

目的探讨新型载银纳米抗菌复合骨填充材料(TiO2-Ag-nHA/PA66)的体外抗菌性能。方法采用抑菌环试验及菌落总数测定法检测不同纳米抗菌复合骨填充材料(A1、A2、A3)对金黄色葡萄球菌及大肠埃希菌的体外抗菌效果;扫描电镜观察其对细菌的抗粘附作用。结果抑菌环试验显示,不同载银纳米抗菌复合骨填充材料对金黄色葡萄球菌和大肠埃希菌均形成明显的抑菌环,以作用24 h抑菌环直径最大,并随作用时间延长,抑菌环直径逐渐缩小。其中银含量为0.64%(质量比)的材料A3的抗菌作用最明显,持续时间最长,其对金黄色葡萄球菌和大肠埃希菌的抑菌作用持续时间分别达到33 d和24 d;菌落总数测定法显示细菌与材料A3接触24 h后,对金黄色葡萄球菌和大肠埃希菌的抗菌率分别为94.18%和85.96%;扫描电镜发现载银材料能够明显减少细菌在材料表面的粘附。结论载银纳米抗菌复合骨填充材料体外对金黄色葡萄球菌及大肠埃希菌有明显抗菌作用,为其应用于慢性骨髓炎术后骨缺损修复提供理论依据。     

The role of conditioning film formation in Pseudomonas aeruginosa PAO1 adhesion to inert surfaces in aquatic environments

Bacterial initial adhesion to inert surfaces in aquatic environments is highly dependent on the surface properties of the substratum, which can be altered significantly by the formation of conditioning films. In this study, the impact of conditioning films formed with extracellular polymeric substances (EPS) on bacterial adhesion was investigated. Adhesion of wild type Pseudomonas aeruginosa PAO1 to slides coated with model EPS components (alginate, humic substances, and bovine serum albumin (BSA)) was examined. Surface roughness of conditioning film coated slides was evaluated by atomic force microscopy (AFM), and its effect on the bacterial initial adhesion was not significant. X-ray photoelectron spectroscopy (XPS) studies were performed to determine the elemental surface compositions of bacterial cells and substrates. Results showed that bacterial adhesion to bare slides and slides coated with alginate and humic substances increased as ionic strength increased. Conversely, BSA coating enhanced bacterial adhesion at low ionic strength but hindered adhesion at higher ionic strength. It was concluded that forces other than hydrophobic and electrostatic interactions were involved in controlling bacterial adhesion to BSA coated surfaces. A steric model for polymer brushes that considers the combined influence of steric effects and DLVO interaction forces was shown to adequately describe the observed bacterial adhesion behaviors.     

Phosphatidylethanolamine Deficiency Impairs Escherichia coli Adhesion by Downregulating Lipopolysaccharide Synthesis,Which is Reversible by High Galactose/Lactose Cultivation

As the initiation step of bacterial infection or biofouling, bacterial adhesion on cells or substrates is generally an optimal target for antibacterial design. Phosphatidylethanolamine (PE) is the principal phospholipid in bacteria, and its function in bacterial adhesion remains unclear. In this study, four E. coli strains including two PE-deficient mutants (PE^?PC^? and PE^?PC^+?strains) and two PE-containing wild-type controls (PE?⁺?PC^? strains) were recruited to investigate the influence of PE deficiency on bacterial adhesion. We found that PE deficiency could impair E. coli adhesion on macrophages (human THP-1-derived and mouse RAW264.7 macrophages) or glass coverslips by downregulating lipopolysaccharide (LPS) biosynthesis, which could be reversible by high galactose/lactose but not glucose cultivation. The data imply that PE play important role in bacterial adhesion probably via affecting LPS biosynthesis and suggest that targeting PE biosynthesis is also a potential antibacterial strategy.     

Nanoscale investigation on adhesion of E. coli to surface modified silicone using atomic force microscopy

Bacterial adhesion on biomaterial surfaces is the initial step in establishing infections and leads to the formation of biofilms. In this study, silicone was modified with different biopolymers and silanes, including: heparin, hyaluronan, and self-assembled octadecyltrichlorosilane (OTS), and fluoroalkylsilane (FAS). The aim was to provide a stable and bacteria-resistant surface by varying the degree of hydrophobicity and the surface structure. The adhesion of Escherichia coli (JM 109) on different modified silicone surfaces was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Mica, an ideal hydrophilic and smooth surface, was employed as a control specimen to study the effect of hydrophobicity and surfaces roughness on bacterial adhesion. AFM probes were coated with E. coli and the force measurements between the bacteria-immobilized tip and various materials surfaces were obtained while approaching to and retracting from the surfaces. A short-range repulsive force was observed between the FAS coated silicone and bacteria. The pull-off force of bacteria to FAS was the smallest among coated surfaces. On the other hand, heparin exhibited a long-range attractive force during approach and required a higher pull-off force in retraction. Both AFM and SEM results indicated that FAS reduced bacterial adhesion whereas heparin enhanced the adhesion compared to pure silicone. The work demonstrates that hydrophobicity cannot be used as a criterion to predict bacterial adhesion. Rather, both the native properties of the individual strain of bacteria and the specific functional structure of the surfaces determine the strength of force interaction, and thus the extent of adhesion.     

Receptor type I and type II binding regions and the peptidyl-prolyl isomerase site of cyclophilin B are required for enhancement of T-lymphocyte adhesion to fibronectin

Cyclophilin B (CyPB), a cyclosporin A (CsA) binding protein, interacts with two types of binding sites at the surface of T-lymphocytes. The type I sites correspond to functional receptors involved in endocytosis and the type II sites to sulfated glycosaminoglycans (GAGs). Mutational analysis of CyPB has revealed that W128, which is part of the CsA-binding pocket, is implicated in the binding to the functional type I receptors and that two amino acid clusters located in the N-terminus ensure the binding to GAGs. The peptidyl-prolyl isomerase activity of CyPB is not required for receptor binding. We have recently demonstrated that CyPB enhances adhesion of peripheral blood T-lymphocytes to fibronectin, a component of the extracellular matrix. We intended to identify additional amino acids involved in the binding of CyPB to its functional type I receptor and to determine regions responsible for the stimulation of peripheral blood T-lymphocyte adhesion. We determined that residues R76, G77, K132, D155, and D158 of the calcineurin (CN) interacting region were implicated in the recognition of type I receptor but not of GAGs. We also found that two different changes in the N-terminal extension that abated binding to GAGs prevented adhesion of peripheral blood T-lymphocytes to coated CyPB, whereas abbrogation of the PPIase activity had no effect. On the other hand, the adhesion of peripheral blood T-lymphocytes to coated fibronectin was not stimulated by CyPB mutants devoid of either type I receptor or GAGs binding activity or by mutants of the PPIase site. Altogether, the results demonstrate that different regions of CyPB are involved in peripheral blood T-lymphocyte activation and imply a novel important physiological function for peptidyl-prolyl isomerase activity.     

人HMGB1酸性尾端对其抗菌活性的影响

为研究人高迁移率族蛋白B1(high-mobility group box-1HMGB1)酸性尾端对其抗菌活 性的影响,提取人外周血单个核细胞总RNA,经RT\|PCR扩增得到编码人HMGB1的cDNA及其缺失酸性尾端的突变体cDNA(mcDNA),原核表达载体pQE\|80L分别表达重组人HMGB1蛋白(rhHMGB1)及缺失酸性尾端的突变体蛋白(mrhHMGB1),经Ni^2+_- NTA亲和层析柱纯化两种蛋白.通过试管稀释法、琼脂扩散法两种体外抗菌实验观察,并比较rhHMGB1mrhHMGB1抗菌活性的差异.实验结果显示,rhHMGB1对大肠杆菌JM109、ATCC2592 2、DH5α有明确的抗菌活性,其抗菌活性强弱依次为JM109>ATCC25922>DH5α,而mrhHMGB1 对大肠杆菌JM109、ATCC25922、DH5α则均无抗菌活性.实验结果表明,人HMGB1的酸性尾端对其抗菌活性的发挥至关重要,此研究为进一步探讨人HMGB1抗菌功能的机制奠定了基础.     

A novel series of 11-O-carbamoyl-3-O-descladinosyl clarithromycin derivatives bearing 1,2,3-triazole group: Design,synthesis and antibacterial evaluation

A series of novel 11-O-carbamoyl-3-O-descladinosyl clarithromycin derivatives bearing the 1,2,3-triazole group were designed, synthesized, and evaluated for their in vitro antibacterial activity. The antibacterial results indicated that most of the target compounds not only increased their activity against resistant bacterial strains, but also partially retained the activity against sensitive bacterial strains compared with clarithromycin. Among them, 13d had the best antibacterial activity against resistant strains, including Streptococcus pneumoniae B1 expressing the ermB gene (16 µg/mL), Streptococcus pneumoniae AB11 expressing the mefA and ermB genes (16 µg/mL) and Streptococcus pyogenes R1 (16 µg/mL), showing >16, 8 and 16-fold higher activity than that of CAM, respectively. Moreover, 13d and 13g exhibited the best antibacterial activity against sensitive bacterial strains, including Staphylococcus aureus ATCC25923 (4 µg/mL) and Bacillus Subtilis ATCC9372 (1 µg/mL). The MBC results showed that the most promising compounds 13d and 13g exhibited antibacterial activity through bacteriostatic mechanism, while the time-kill kinetic experiment revealed bactericidal kinetics of 13g from microscopic point of view. In vitro antibacterial experiments and molecular docking results further confirmed that it was feasible to our initial design strategy by modifying the C-3 and C-11 positions of clarithromycin to increase the activity against resistant bacteria.     

Antibacterial acitivity of the peptide complex isolated from the preparation of leukocytic interferon

A complex of low-molecular cationic peptides having an anti-bacterial effect with respect to Gram-positive and Gram-negative bacteria was isolated from the preparation of leukocytic interferon. The antibacterial action of the peptide complex was experimentally studied in vitro. The study revealed that the degree of the antibacterial activity of the peptide complex depended on the concentration of the bacterial culture under study, the ionic power of the incubation medium and did not depend on the presence of the products of bacterial vital activity in the growth medium. The antibacterial action of the peptide complex on the test cultures of Gram-positive and Gram-negative bacteria, as well as on the cultures of bacteria isolated from patients with infectious inflammatory diseases of the organs of the urinary system, was established. These results opened prospects for the development of fundamentally new antibacterial preparation on the basis of the peptide complex obtained in our studies.     

In vitro system for high-throughput screening of random peptide libraries for antimicrobial peptides that recognize bacterial membranes.

Antibacterial peptides have been isolated from a wide range of species. Some of these peptides act on microbial membranes, disrupting their barrier function. With the increasing development of antibiotic resistance by bacteria, these antibacterial peptides, which have a new mode of action, have attracted interest as antibacterial agents. To date, however, few effective high-throughput approaches have been developed for designing and screening peptides that act selectively on microbial membranes. In vitro display techniques are powerful tools to select biologically functional peptides from peptide libraries. Here, we used the ribosome display system to form peptide-ribosome-mRNA complexes in vitro from nucleotides encoding a peptide library, as well as immobilized model membranes, to select specific sequences that recognize bacterial membranes. This combination of ribosome display and immobilized model membranes was effective as an in vitro high-throughput screening system and enabled us to identify motif sequences (ALR, KVL) that selectively recognized the bacterial membrane. Owing to host toxicity, it was not possible to enrich any sequence expected to show antimicrobial activity using another in vitro system, e.g. phage display. The synthetic peptides designed from these enriched motifs acted selectively on the bacterial model membrane and showed antibacterial activity. Moreover, the motif sequence conferred selectivity onto native peptides lacking selectivity, and decreased mammalian cell toxicity of native peptides without decreasing their antibacterial activity.     

Fibronectin and proteolytic fragments of fibronectin interfere with the adhesion of Staphylococcus epidermidis to plastic

W.M. DUNNE AND E.M. BURD. 1993. The adhesion of five strains of slime-positive Staphylococcus epidermidis to plastic microwells was significantly diminished ( P < 0.005) in a concentration-dependent fashion when wells were previously coated with increasing concentrations (1.6–13.1 μg cm^-2) of human fibronectin (FN). The adhesion of four of five strains was significantly reduced when wells were coated with 3.2 μg cm^-2 of FN and at concentrations ≥6.5 μg cm^-2 the adhesion of all slime-positive strains was significantly reduced. The coating of microwells with chymotryptic fragments of FN containing the heparin-binding, gelatin-binding, or cell-binding domains also reduced bacterial adhesion but none of the fragments exceeded the anti-adhesive activity of intact FN. A comparison of FN-coated or albumin-coated microwells showed that both proteins caused a significant reduction in the adhesion of test strains to plastic but that the anti-adhesive activity of FN was greater than albumin at all concentrations tested. The adhesion of the slime-negative phase variant of one of the test strains to plastic was neither enhanced nor reduced by FN coating indicating that the production of an exopolysaccharide by Staph. epidermidis influences interactions with protein-coated surfaces. These results support the contention that FN does not mediate the adhesion of all strains of Staph. epidermidis to plastic surfaces.     

大蒜素抗变异链球菌的致龋效果

目的研究大蒜素对口腔变异链球菌生长及其菌斑生物膜粘附的抑制作用。方法二倍稀释法梯度稀释测最小抑菌浓度(minimum inhibitory concentration,MIC),将MIC以上2个梯度浓度对应的培养物涂布于BHI培养基上进行次代培养获得最低杀菌浓度(minimum bactericidal concentration,MBC);酶标仪测A值观察不同浓度大蒜素抑菌效应;抑制产酸试验观察抑制细菌产酸效应;结晶紫法研究亚抑菌浓度提取物对变异链球菌粘附能力及生物膜总量的影响;采用激光共聚焦荧光显微镜(laser scanning confocal microscopy,LSCM)观察常态牙菌斑生物膜生长过程中及药物处理后牙菌斑生物膜中死菌和活菌的构成,研究其对牙菌斑生物膜结构和活性的影响。结果抑菌试验中,得到大蒜素MIC为12.8 mg/L,MBC为25.8 mg/L。MIC及亚抑菌浓度抑菌试验显示均有一定的抑菌性,抑制率为2.17%～67.12%,并且抑菌性与浓度梯度成正相关。产酸试验显示24 h内大蒜素明显抑制细菌产酸(P0.01),细菌粘附试验结果显示大蒜素在MIC时生物膜的生成速度最慢,生物膜的总量最低(P0.01)。共聚焦荧光显微镜可见大蒜素组随药物浓度增加,菌斑生物膜较薄,绿色的活菌及团块明显减少,抑制生物膜的生长。结论大蒜素对变异链球菌生长、产酸与粘附有一定抑制作用。     

Adhesion of food-borne bacteria to stainless steel is reduced by food conditioning films

Aims:  Preconditioning of stainless steel with aqueous cod muscle extract significantly impedes subsequent bacterial adhesion most likely due to repelling effects of fish tropomyosin. The purpose of this study was to determine if other food conditioning films decrease or enhance bacterial adhesion to stainless steel.
Methods and Results:  Attachment of Pseudomonas fluorescens AH2 to stainless steel coated with water-soluble coatings of animal origin was significantly reduced as compared with noncoated stainless steel or stainless steel coated with laboratory substrate or extracts of plant origin. Coating with animal extracts also decreases adhesion of other food-relevant bacteria. The manipulation of adhesion was not attributable to growth inhibitory effects. Chemical analysis revealed that the stainless steels were covered by homogenous layers of adsorbed proteins. The presence of tropomyocin was indicated by appearance of proteins with similar molecular weight based in sodium dodecyl sulfate–polyacrylamide gel electrophoresis, in several extracts that reduced adhesion but also extracts not containing this protein reduced bacterial adhesion, indicating that several molecular species may be involved in the phenomenon.
Conclusions:  It is a common perception that food materials facilitate bacterial adhesion to surfaces; however, this study demonstrates that aqueous coatings of food origin may actually reduce bacterial adhesion.
Significance and Impact of the Study:  Compounds from food extracts may potentially be used as nontoxic coatings to reduce bacterial attachment to inert surfaces.     

Antibacterial and antibiofilm effects of silver nanoparticles against the uropathogen Escherichia coli U12

The drug-resistant bacterial strains' emergence increases day by day. This may be a result of biofilm presence, which protects bacteria from antimicrobial agents. Thus, new approaches must be used to control biofilm-related infections in healthcare settings. In such a study, biological silver nanoparticles were introduced in such a study as an anti-biofilm agent against multidrug-resistant E. coli U12 on urinary catheters. Seven different silver nanoparticles concentrations were tested for their antimicrobial activities. Also, anti-biofilm activities against E. coli U12 were tested. Using the dilution method, the silver nanoparticles concentration of 85 μg/ml was the MIC (Minimum Inhibitory Concentration) that had excellent biocompatibility and showed significant antibacterial activity against E. coli U12. Scanning electron microscopy (SEM) confirmed that the highest efficient dose of silver nanoparticles was 340 μg/ml at 144 h that reduced adhesion of E. coli U12 to the urinary catheter. E. coli U12 cells ruptured cell walls and cell membranes after being examined using transmission electron microscopy (TEM). Thus, biologically prepared silver nanoparticles could be used to coat medical devices since it is effective and promising to inhibit biofilm formation by impregnating urinary catheters with silver nanoparticles.     

Antibacterial activity of plastics coated with silver-doped organic-inorganic hybrid coatings prepared by sol-gel processes

Silver-doped organic-inorganic hybrid coatings were prepared starting from tetraethoxysilane- and triethoxysilane-terminated poly(ethylene glycol)-block-polyethylene by the sol-gel process. They were applied as a thin layer (0.6-1.1 microm) to polyethylene (PE) and poly(vinyl chloride) (PVC) films and the antibacterial activity of the coated films was tested against Gram-negative (Escherichia coli ATCC 25922) and Gram-positive (Staphylococcus aureus ATCC 6538) bacteria. The effect of several factors (such as organic-inorganic ratio, type of catalyst, time of post-curing, silver ion concentration, etc.) was investigated. Measurements at different contact times showed a rapid decrease of the viable count for both tested strains. The highest antibacterial activity [more than 6 log reduction within 6 h starting from 106 colony-forming units (cfu) mL-1] was obtained for samples with an organic-inorganic weight ratio of 80:20 and 5 wt % silver salt with respect to the coating. For the coatings prepared by an acid-catalyzed process, a high level of permanence of the antibacterial activity of the coated films was demonstrated by repeatedly washing the samples in warm water or by immersion in physiological saline solution at 37 degrees C for 3 days. The release of silver ions per square meter of coating is very similar to that previously observed for polyamides filled with metallic silver nanoparticles; however, when compared on the basis of Ag content, the concentration of silver ions released from the coating is much higher than that released from 1 mm thick specimens of polyamide (PA) filled with silver nanoparticles. Transparency and good adhesion of the coating to PE and PVC plastic substrates without any previous surface treatment are further interesting features.     

Surpassing nature: rational design of sterile-surface materials

The rise of multidrug-resistant pathogens and recalcitrance of biofilm infections present a formidable challenge to combating infectious diseases. There are numerous disinfectants and antiseptics for treating materials in hospitals and community settings, and devices such as catheters impregnated with anti-infectives have been introduced into practice. However, there are many limitations of materials impregnated with a leaching antibacterial agent. Recently, non-leaching, permanent, sterile-surface materials have been developed in which one end of a long-chained hydrophobic polycation containing antimicrobial monomers is attached covalently to the surface of a material, for example, cotton or plastic. The polymeric chain allows the antimicrobial moieties to permeate into, and kill, the cells of the pathogen. These sterile-surface materials kill both air- and waterborne pathogens and are not susceptible to existing resistance mechanisms.