Showing papers on "Biofilm matrix published in 1994"

Direct measurement of chlorine penetration into biofilms during disinfection.

Abstract: Transient chlorine concentration profiles were measured in biofilms during disinfection by use of a microelectrode developed for this investigation. The electrode had a tip diameter of ca. 10 microm and was sensitive to chlorine in the micromolar range. The biofilms contained Pseudomonas aeruginosa and Klebsiella pneumoniae. Chlorine concentrations measured in biofilms were typically only 20% or less of the concentration in the bulk liquid. Complete equilibration with the bulk liquid did not occur during the incubation time of 1 to 2 h. The penetration depth of chlorine into the biofilm and rate of penetration varied depending on the measurement location, reflecting heterogeneity in the distribution of biomass and in local hydrodynamics. The shape of the chlorine profiles, the long equilibration times, and the dependence on the bulk chlorine concentration showed that the penetration was a function of simultaneous reaction and diffusion of chlorine in the biofilm matrix. Frozen cross sections of biofilms, stained with a redox dye and a DNA stain, showed that the area of chlorine penetration overlapped with nonrespiring zones near the biofilm-bulk fluid interface. These data indicate that the limited penetration of chlorine into the biofilm matrix is likely to be an important factor influencing the reduced efficacy of this biocide against biofilms as compared with its action against planktonic cells.

The challenge to analyse extracellular polymers in biofilms

Abstract: Extracellular polymeric substances (EPS) represent a major fraction of microbial biofilms. The EPS within biofilms form a 3-dimensional network which is called biofilm matrix. The EPS immobilize the microbial cells within the biofilm and at the interface (Neu and Marshall 1990). The matrix is highly hydrated as it consists of more than 95% water. For this reason the biofilm matrix can be regarded as a layer of immobilized water (Cooksey 1992). So far the presence of the biofilm matrix has been demonstrated by various electron microscopic techniques which have been adapted from studies on microbial cell surfaces (Hancock and Poxton 1988; Mozes et al. 1991). The significance of EPS in biofilms has been elaborated in several review articles (Characklis 1973a; Characklis 1973b; Christensen 1989; Christensen and Characklis 1990; Geesey 1982; Neu 1992a). Nevertheless, the important compositional aspects of this matrix, mainly polysaccharides but also proteins, have been neglected in many studies on biofilms.

Effectiveness of antibiotics on the autochthonous Escherichia coli of mice in the intestinal biofilm versus its planktonic phase.

Abstract: The effectiveness of antibiotics was tested on the autochthonous Escherichia coli in biofilm mode of growth in large bowel pieces as well as on the predominant faecal E. coli isolated from the same SPF mice in planktonic phase of growth. Aminoglycoside antibiotics, chloramphenicol, oxytetracycline, erythromycin and lincomycin-clindamycin treatment had a very limited effect in the intestinal biofilm. Surprising ineffectiveness was found with polymyxins: polymyxin B showed a Minimal Bactericidal Dose of 0.78 microgram in planktonic phase, while it was 400 micrograms for E. coli incorporated in the biofilm matrix. In contrast to the above groups of antibiotics, the beta-lactam drugs were effective both in the biofilm and in the planktonic phase growth of E. coli and their derivatives with broad or broader spectrum exerted an increased biofilm activity. Polymyxin B showed no sign of penetration into the colonic mucus, but on the other side ampicillin concentrated about three-four times in the intestinal matrix.