Kinetics Of Adherence Research Articles

Adherence of a Clinical Strain of <i>Mycoplasma fermentans</i> to Human Cultured Epithelial Cells

This study compares the kinetics of adherence of both the prototype strain PG-18 and the recently clinically isolated strain P-140 of Mycoplasma fermentans to HEp-2 cells. M. fermentans may induce respiratory and genitourinary tract infections. We investigated the presence of putative adhesins from strain P-140. A surface protein of 47 kDa, labeled SP47, isolated from M. fermentans P-140, seems to be involved in acterial adherence on HEp-2 cells; this study could allow helping understand the interaction between mycoplasmas and their hosts. Anti-SP47 antibodies inhibited the formation of bacterial clusters and adherence to cultured cells, quantified by ELISA. M. fermentans P-140 was more efficient at adhering to cultured HEp-2 cells than PG-18.

Adherence kinetics, resistance to benzalkonium chloride and microscopic analysis of mixed biofilms formed by Listeria monocytogenes and Pseudomonas putida

Comparison between the resistance to BAC and the microscopic structure between mixed-species biofilms formed by different strains of Listeria monocytogenes and Pseudomonas putida CECT 845 under different scenarios and that obtained by the corresponding monospecies L. monocytogenes biofilm was carried out. The association of P. putida with L. monocytogenes quickens biofilm formation and increases significantly (p < 0.05) the BAC-resistance of the biofilm after 4 days of incubation at 25 °C respecting to that formed by monospecies biofilms. According with the adherence profiles of P. putida, two different patterns of association between both species (A and B) were identified, being type A pattern found in the mixed biofilms much more resistant to BAC. After 11 days of incubation, a destructuration of mixed biofilms occurred in all experimental assays, being in 2 out of 5 experimental cases (4032 and BAC-adapted 5873 on polypropylene) accompanied by a sharp decrease in the number of adhered cells. Microscopic analyses demonstrated that complex three-dimensional microscopic structure showed the highest resistance to BAC (4032-SS). Obtained results clearly highlight that to improve disinfection protocols for assuring food safety, it is necessary to mimick those bacterial association that occur in nature.

Mechanisms of skin adherence and invasion by dermatophytes

Dermatophytes are keratinophilic fungi that can be pathogenic for humans and animals by infecting the stratum corneum, nails, claws or hair. The first infection step consists of adherence of arthroconidia to the stratum corneum. The mechanisms and the kinetics of adherence have been investigated using different in vitro and ex vivo experimental models, most notably showing the role of a secreted serine protease from Microsporum canis in fungal adherence to feline corneocytes. After germination of the arthroconidia, dermatophytes invade keratinised structures that have to be digested into short peptides and amino acids to be assimilated. Although many proteases, including keratinolytic ones, have been characterised, the understanding of dermatophyte invasion mechanisms remains speculative. To date, research on mechanisms of dermatophyte infection focused mainly on both secreted endoproteases and exoproteases, but their precise role in both fungal adherence and skin invasion should be further explored.

Comparison between the adherence of a rigid axisymmetrical cone and a truncated one, in adhesive contact on an elastic half-space

We compare the equilibrium contacts and the kinetics of adherence of an axisymmetrical rigid cone and a flat-ended one with the same angle, applied against the flat and smooth surface of a soft elastomer sample (unfilled vulcanized natural rubber, cured with dicumyl peroxide), with the help of fracture mechanics concepts which can easily be introduced in this class of problems by using Sneddon's solution (1965) of Boussinesq's problem extended to all axisymmetric adhesive punches with a convex profile. The kinetics of adherence are measured when an imposed tensile force is applied in order to disturb the size of the contact area. Variations of the strain energy release rate, G, and of the associated dissipation function | =(G m w)/w, where w is the Dupré energy of adhesion, are studied as a function of the parameter, a T ± V, in which V is the crack propagation speed at the interface between a cone and a truncated one made of glossy Plexiglass®, and the rubber sample (the limit of the contact is considered as a crack tip), and a T , is the shift factor of the Williams-Landel-Ferry transformation. As expected, a master curve | (V) is found, confirming the variation of | as the power function V 0.55 , at fixed temperature, as recently established by Barquins et al. in adherence of a flat ended sphere and cone in pull-off/push-on tests, adherence and rolling of cylinders experiments and rebound of balls tests, with the same elastomer. Present results lead to propose one to write | =k ± (a T ± V) 0.55 , k=2520 and V being valued using S.I. units, for the reference temperature θ=25°C, with a quite good accuracy in the order of 1%.

Adhésion et cinétique de décollement d'un cône rigide tronqué en contact avec un élastomère souple

The equilibrium contact and the kinetics of adherence, at an imposed applied load, of a rigid flat-ended cone in contact with the flat and smooth surface of a soft elastomer sample (unfilled natural rubber) are examined with the help of fracture mechanics concepts. The variation of the dissipation function Φ=( G− w)/ w, where G is the strain energy release rate and w the Dupré energy of adhesion, is studied as a function of the crack propagation speed V at the interface between the flat-ended rigid cone and the elastic solid. As expected, a master curve Φ( V) is found, confirming the variation of Φ as the 0.55 power function of V, as recently established by Barquins et al. in adherence experiments, with the same rubber-like material. To cite this article: S. Bouissou, M. Barquins, C. R. Physique 3 (2002) 239–245.

Adhesive Contact And Kinetics Of Adherence Of A Rigid Conical Punch On An Elastic Half-space (natural Rubber)

Abstract The equilibrium contact of a rigid conical punch, applied against the flat and smooth surface of a soft elastomer sample (unfilled natural rubber), is studied with the help of fracture mechanics concepts which can be easily introduced in this class of problems by using Sneddon's solution (Int. J. Eng. Sci. 3 (1965) p.47) of Boussinesq's problem extended to all axisymmetric adhesive punches with a convex profile as a cone. The kinetics of adherence is measured when an imposed tensile force is applied in order to disturb the size of the contact area. Variations of the strain energy release rate G and of the associated dissipation function Φ =( G − w )/ w , where w is the Dupre energy of adhesion, are studied as a function of the crack propagation speed V at the interface between a cone made of plexiglass (PMMA) and the rubber sample (the limit of the contact is considered as a crack tip). As expected, a master curve Φ ( V ) is found, confirming the variation of Φ as the 0.55 power function of V , as recently established by Barquins et al. in adherence of flat-ended spheres in pull-off/push-on tests, adherence and rolling of cylinders experiments and rebound of balls tests, with the same elastic rubber-like material.

État d'équilibre et cinétique de décollement d'un cylindre rigide en contact avec un élastomère souple

The equilibrium contact of a rigid cylinder applied against the flat and smooth surface of a soft elastomer sample (natural rubber) is examined and a method is proposed for evaluating both the Young's modulus E of the rubber-like material tested and the Dupré energy of adhesion w using a presentation of results similar to that recently described by Chaudhury et al. from the previous work of Barquins. New results on the kinetics of adherence at imposed normal load are presented. They consist of a study of variations of the strain energy release rate G and of the associate dissipation function Φ = ( G - w)/w as a function of the crack propagation speed V at the interface between the rigid cylinder and the elastic solid. As expected, a master curve Φ(V) is found, confirming the variation of Φ as the 0.55 power function of V, as recently established in rolling and rebound experiments by Barquins and Charmer with the same rubber-like material.

Adhesive contact and kinetics of adherence between a rigid cylinder and an elastomeric solid

The equilibrium contact of a rigid cylinder applied against the flat and smooth surface of a soft elastomer sample (natural rubber) is examined, and a method is proposed for evaluating both the Young modulus E of the rubber-like material tested and the Dupré energy of adhesion w using a results similar to that recently proposed by Chaudhury et al. from the previous work of Barquins. New results on the kinetics of adherence at imposed normal load are presented. They comprise a study on variations of the strain energy release rate G and of the associate dissipation function Φ=( G− w)/ w as a function of the crack propagation speed V at the interface between the rigid cylinder and the elastic solid. As expected, a master curve Φ( V) is found, confirming the variation of Φ as the 0.55 power function of V, as recently established in rolling and rebound experiments with the same rubber-like material (natural rubber).

Radiopacity additives in silicone stent materials reduce in vitro bacterial adherence

In vitro adherence of the nosocomial pathogensPseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, andCandida albicans to select radiopaque silicone compounds was lower than that observed for the base silicone (p<0.03). Except forE. coli ATCC 11775 andCandida albicans, all microorganisms showed significantly lower adherence to a silicone compound impregnated with tantalum in comparison with a silicone compound impregnated with barium sulfate (p<0.05). Surface hydrophobicity of the silicone compounds did not show a direct correlation with the concentration of radiopacity additives or with degree of bacterial adherence. Scatchard analyses of data indicated that the number of adherence sites forP. aeruginosa on the base silicone, BaSO4-silicone, and Ta-silicone were 9.2×106 per mm2, 6.1×106 per mm2, and 3.7×106 per mm2 respectively. As determined by the Langmuir adsorption isotherm, the dissociation constants for adheredP. aeruginosa to the base silicone, BaSO4-silicone, and Ta-silicone were 2.50×103 mm4, 1.45×103 mm4, and 6.27×103 mm4 respectively.Pseudomonas aeruginosa demonstrated first order kinetics of adherence to the silicone compounds with a half saturation time of 4.15 h for the base silicone, 1.06 h for the BaSO4-silicone, and 2.14 h for the Ta-silicone. The use of Ta-silicone stents may delay the development of ascending urinary tract infections.