Showing papers by "Mel Rosenberg published in 1990"

Microbial cell surface hydrophobicity

Abstract: Microbial cell surface hydrophobicity: history, measurement and significance Nature of the hydrophobic effect Microbial hydrophobicity and fermentation technology Role of hydrophobic interactions in microbial adhesion to plastics used in medical devices Hydrophobicity of proteins and bacterial fimbriae Adhesion of bacteria to plant cells Hydrophobicity in the aquatic environment Changes in bacterial surface hydrophobicity during morphogenesis and differentiation Cell surface hydrophobicity of medically important fungi, especially Candida species Significance of hydrophobicity in the adhesiveness of pathogenic Gram-negative bacteria Hydrophobic characteristics of Staphylococci Relative importance of surface free energy as a hydrophobicity measure in bacterial adhesion to solid surfaces Hydrophobicity of Group A Streptococci to host cells Hydrophobicity of oral bacteria

Mechanism of enhancement of microbial cell hydrophobicity by cationic polymers.

Abstract: Polycationic polymers have been noted for their effects in promoting cell adhesion to various surfaces, but previous studies have failed to describe a mechanism dealing with this type of adhesion. In the present study, three polycationic polymers (chitosan, poly-L-lysine, and lysozyme) were tested for their effects on microbial hydrophobicity, as determined by adhesion to hydrocarbon and polystyrene. Test strains (Escherichia coli, Candida albicans, and a nonhydrophobic mutant, MR-481, derived from Acinetobacter calcoaceticus RAG-1) were vortexed with hexadecane in the presence of the various polycations, and the extent of adhesion was measured turbidimetrically. Adhesion of all three test strains rose from near zero values to over 90% in the presence of low concentrations of chitosan (125 to 250 micrograms/ml). Adhesion occurred by adsorption of chitosan directly to the cell surface, since E. coli cells preincubated in the presence of the polymer were highly adherent, whereas hexadecane droplets pretreated with chitosan were subsequently unable to bind untreated cells. Inorganic cations (Na+, Mg2+) inhibited the chitosan-mediated adhesion of E. coli to hexadecane, presumably by interfering with the electrostatic interactions responsible for adsorption of the polymer to the bacterial surface. Chitosan similarly promoted E. coli adhesion to polystyrene at concentrations slightly higher than those which mediated adhesion to hexadecane. Poly-L-lysine also promoted microbial adhesion to hexadecane, although at concentrations somewhat higher than those observed for chitosan. In order to study the effect of the cationic protein lysozyme, adhesion was studied at 0 degree C (to prevent enzymatic activity), using n-octane as the test hydrocarbon. Adhesion of E. coli increased by 70% in the presence of 80 micrograms of lysozyme per ml. When the negatively charged carboxylate residues on the E. coli cell surface were substituted for positively charged ammonium groups, the resulting cells became highly hydrophobic, even in the absence of polycations. The observed "hydrophobicity" of the microbial cells in the presence of polycations is thus probably due to a loss of surface electronegativity. The data suggest that enhancement of hydrophobicity by polycationic polymers is a general phenomenon.

Effect of cetylpyridinium chloride on microbial adhesion to hexadecane and polystyrene.

Abstract: Microbial adhesion at the oil-water interface is a subject of both basic interest (e.g., as a technique for the measurement of hydrophobicity) and applied interest (e.g., for use in two-phase oil-water mouthwashes for the desorption of oral microorganisms). In general, surfactants inhibit microbial adhesion to oils and other hydrophobic surfaces. In the present study, we demonstrated that the cationic surfactant cetylpyridinium chloride (CPC) significantly enhanced microbial adhesion to hexadecane and various oils, as well as to the solid hydrophobic surface polystyrene. CPC increased adhesion to hexadecane of Escherichia coli, Candida albicans and Acinetobacter calcoaceticus MR-481 and of expectorated oral bacteria from near 0% to over 90%. The CPC concentration required for optimal enhancement of adhesion was a function of the initial cell density. This phenomenon was inhibited by high salt concentrations and, in the case of E. coli, by a low pH. CPC-pretreated cells were able to bind to hexadecane, but CPC-pretreated hexadecane was unable to bind untreated cells. Another cationic, surface-active antimicrobial agent, chlorhexidine gluconate, was similarly able to promote microbial adhesion to hexadecane. The results suggest that (i) CPC enhances microbial adhesion to hexadecane by binding via electrostatic interactions at the cell surface, thus diminishing surface charge and increasing cell surface hydrophobicity, and (ii) this phenomenon may have applications in oral formulations and in the use of hydrocarbon droplets as a support for cell immobilization.

Estimation of dental plaque levels and gingival inflammation using a simple oral rinse technique.

Abstract: A simple, non-invasive test (the Oratest) has recently been proposed, which provides an estimate of oral microbial levels based on the rate of oxygen depletion in expectorated milk samples. Following 30 seconds of vigorous rinsing with sterilized milk, 3 ml of the expectorate is added to a test tube containing the redox indicator, methylene blue, and the time required for a color change from blue (i.e., aerobic conditions) to white (anaerobic conditions) at the bottom of the test tube is recorded. In the present study, Oratest scores were compared to clinical parameters (Plaque Index [PI] and Gingival Index [GI]) in a group of 49 volunteers. Significant correlations were found between the logarithm of Oratest results and PI (r= –0.58; P = 0.001) as well as GI (r= –0.66; P = 0.001). The data indicate that the Oratest provides a reliable estimate of gingival inflammation, thus extending the previously reported strong correlations between Oratest scores and microbial counts. The data suggest that the Oratest...

An innovative method of monitoring denture hygiene.

Abstract: A simple and rapid test for measuring oral hygiene was recently developed. It is based on the rate of oxygen consumption of oral expectorates of milk. This investigation modified the test to study denture hygiene. The dentures of 20 patients were immersed in 10 mL of sterile milk. After a 2-minute agitation, 3 mL of milk was added to test tubes containing methylene blue. The time required for color change at the bottom of the test tube, which is indicative of the rate of oxygen consumption, was recorded. For comparison with visual plaque accumulation, the dentures were coated with disclosing solution and the extent of plaque was scored by three examiners. A correlation was found between the plaque index scores and results of the milk test ( r = −0.64; p

Inhibition of the cooperative adhesion of Streptococcus sanguis to hydroxylapatite.

Abstract: The adhesion of Streptococcus sanguis to hydroxylapatite is a process involving several adhesins and receptors. Binding isotherms and Scatchard plots of the adhesion suggest that cooperative interactions occur at low cell densities. It was found that sulfolane, a hydrophobic-bond diluent, was capable of inhibiting the cooperative adhesion of S. sanguis to saliva-coated hydroxylapatite beads. Sodium thiocyanate, a chaotropic agent, inhibited not only cooperative adhesion, but also the adhesion thought to result from non-cooperative interactions. It is suggested that strong chaotropic agents may not only inhibit adhesin-receptor complexes, but also may influence the secondary/tertiary structures of interacting species.