Microbial adhesion to biomaterials and infections of the urogenital tract

Evaluating protein attraction and adhesion to biomaterials with the atomic force microscope

Failure of implanted biomaterials is commonly due to nonspecific protein adsorption, which in turn causes adverse reactions such as the formation of fibrous capsules, blood clots, or bacterial biofilm infections. Current research efforts have focused on modifying the biomaterial interface to control protein reactions. Designing biomaterial interfaces at the molecular level, however, requires an experimental technique that provides detailed, dynamic information on the forces involved in protein adhesion. The goal of this study was to develop an atomic force microscope (AFM)-based technique to evaluate protein adhesion on biomaterial surfaces. In this study, the AFM was used to evaluate (i) protein-protein, (ii) protein-substrate, and (iii) protein-dextran interactions. The AFM was first used to measure the pull-off forces between bovine serum albumin (BSA) tips/BSA surfaces and BSA tips/anti-BSA surfaces. Results from these protein-protein studies were consistent with the literature. More importantly, the successful measurement of antibody-antigen binding interactions demonstrates that both the BSA and anti-BSA proteins retain their folded conformation and remain functional following our immobilization protocol. The AFM was also used to quantify the physiochemical interactions of proteins during adhesion to various self-assembled monolayers (SAMs) and dextran-coated substrates representative of potential biomaterial interface modifications. Dextran, which renders surfaces very hydrophilic, was the only surface coating that BSA protein did not adhere to. Hydrophobic interactions were not found to play a significant role in BSA adhesion. Therefore, the dextran molecules may resist protein adhesion by repulsive steric effects or hydration pressure. Moreover, the AFM-based methodology provides dynamic, quantitative information about protein adhesion at the nanoscale level.

Role of chemical interactions in bacterial adhesion to polymer surfaces

Development of biomaterial-related infections is attracting an increasing interest due to the significant percentage of implant failure in the hospital care. Recent literature puts in evidence the dependence of the infection risk on the different biomaterials used, because of the different interactions between material surface and micro-organisms. Despite this, the mechanisms underlying the adhesion of bacteria to the biomaterial surface are still unclear. Aim of this work is to study the initial events of the processes responsible for the bacterial adhesion on polymers in order to prevent the development of bacterial infections and the consequent failure and replacement of biomedical devices. Electrostatic and Lifshitz-van der Waals forces are usually considered responsible for the interactions at the biomaterial interface. A new term that involves Lewis acid-base interactions is here introduced to better describe the bacterial adhesion to the polymer surface. Two requirements are needed to test this hypothesis: the development of an ideal polymeric surface in terms of chemical and morphological properties and the choice of a specific bacterial strain to be utilized as "probe". Experiments were worked out using an Escherichia coli (Gram-) strain that represent one of the principal isolates from infected biomaterial implants and its adhesion was investigated on polymers having different acid/basic character. The findings indicate that the bacterial adhesion is influenced by the chemical properties of the polymeric surface. These results may be interpreted taking into account a mechanism in which the acid/base (Lewis) interaction plays an important role.

Biomaterials used in urology: current issues of biocompatibility, infection, and encrustation

This review focuses on the biomaterials used in urology, in particular, the properties of urethral catheters and ureteral stents currently being used in clinical practice. The importance of biomaterial type, biocompatibility, and encrustations are discussed and explained. Current management of bacterial infection and the importance of biofilms are presented, with recommendations based on published information.

Possible role of alpha-1-microglobulin in mediating bacterial attachment to model surfaces

Urine proteins in the molecular weight range of 9-137 kDa deposit to an equal extent from pooled human urine onto glass (12.7 +/- 1.9 micrograms/cm) and polystyrene (11.8 +/- 1.8 micrograms/cm). Selective desorption of the proteins was achieved by washing with water or water/isopropanol mixtures. Irrespective of the washing process, proteins of molecular weight greater than 90 kDa remained associated with both surfaces while water washings alone removed most low molecular weight material. A 29 kDa protein, alpha-1-microglobulin, was removed from glass by water washing but required a 30% (v/v) isopropanol wash to desorb from polystyrene, implying attachment via hydrophobic bonding. The adhesion to polystyrene surfaces of Pseudomonas aeruginosa B4, a clinical isolate from a urinary tract infection (UTI), was strongly associated with the presence of alpha-1-microglobulin, which may be acting as a mediator of bacterial adhesion.

Adhesion of Lactobacillus species in urine and phosphate buffer to silicone rubber and glass under flow

Coating uroepithelial cells or catheter materials with lactobacilli has been shown to retard the development of a uropathogenic biofilm, with biosurfactant production and strong adhesion being two prerequisite properties of the Lactobacillus strains to be employed. In this paper, adhesion of six selected Lactobacillus strains to silicone rubber and glass in urine and in a phosphate buffer was studied using a parallel plate flow chamber. In addition, adhesive cell surface properties of the lactobacilli, i.e. the pH dependences of their zeta potentials and their hydrophobicities by water contact angles, were determined. L. acidophilus ATCC 4356 and L. fermentum B54 were the only strains showing significant adhesion to both hydrophobic silicone rubber and hydrophilic glass, possibly by virtue of their high cell surface hydrophobicities (water contact angles of 68 and 75 degrees, respectively) and small zeta potentials (-10.0 and -8.1 mV in buffer, respectively). Both hydrophobic Lactobacillus strains adhered less well in urine than in buffer. The remaining Lactobacillus strains studied were hydrophilic, with water contact angles between 25 and 36 degrees, and had highly negative zeta potentials, reaching -37.7 mV in buffer. Adhesion of these highly negatively charged, hydrophilic strains in buffer was essentially absent, while for some of these strains minor adhesion in urine was observed. This study demonstrates that the adhesion of lactobacilli to substrata differs with strain hydrophobicity and charge, and that urinary components can affect the ability of hydrophilic Lactobacillus strains to adhere to substrata.

Influence of lactobacilli on the adhesion of Staphylococcus aureus and Candida albicans to fibers and epithelial cells

The ability of organisms to adhere to and form biofilms on fibrous materials is believed to be an important initiating step in the induction of several diseases, such as toxic shock syndrome. Using an in vitro assay, a moderately hydrophobic strain of Staphylococcus aureus (water contact angle 35 degrees) and a hydrophilic Candida albicans (shown by a hexadecane test) were highly adherent to commercial diaper fibers. The lumen side of the diaper was porous and the fibers were very hydrophobic (> 140 degrees), but the internal section was very hydrophilic (0 degrees), presumably for lus strains was present. Surfaces precoated with lactobacilli inhibited staphylococcal adhesion by 26-97%, and candida by 0-67%. When the lactobacilli were used to challenge adherent pathogens, there was 99% displacement of the S. aureus and up to 91% displacement of C. albicans. Hydrophobic L. acidophilus 76 (54 degrees) and T-13 (80 degrees) were the most effective of five Lactobacillus isolates tested at interference by precoating. The moderately hydrophilic L. casei var rhamnosus GR-1 (33 degrees) was the most effective at displacing the yeast. Experiments with uroepithelial cells also showed that the lactobacilli could significantly interfere with the adhesion of both pathogens to the cells. The results demonstrate the rapidity with which two pathogens adhered to fibers and epithelial cells, and raised the possibility that members of the normal female urogenital flora might interfere with infections caused by these organisms.

Applications from bacterial adhesion and biofilm studies in relation to urogenital tissues and biomaterials: a review

The urogenital tract, particularly of the adult female, is the habitat for many species of microorganisms. These populations are in a state of flux, are susceptible to disruption by antibiotics and spermicides, and are exposed to many different biomaterial substrata. Infections of the genital area and bladder are common, and are invariably initiated by microbial adhesion to surfaces. This review examines the actual and potential applications to industry and to patients emerging from the study of bacterial adhesion to surfaces.