Sessile Bacterial Cells Research Articles

Bacterial Attachment and Initiation of Biofilms on the Surface of Copper Containing Stainless Steel

Type 304 stainless steel, copper containing stainless steel, and oxygen free copper were subjected to antibacterial tests and short term exposure experiments in a laboratory. Antibacterial tests showed that the copper containing stainless steel, as well as oxygen free copper, was antibacterial, yet the antibacterial activity of the copper containing stainless steel was lower than that of the oxygen free copper. In short term exposure experiments, the copper containing stainless steel, as well as type 304 stainless steel, didn't sterilize planktonic bacterial cells, while the oxygen free copper reduced the number of alive planktonic bacterial cells. The copper containing stainless steel did not protect itself from bacterial adhesion, but sterilized about 75 % of sessile bacterial cells and reduced formation of biofilms on its surface. Such experimental results indicate that the copper containing stainless steel is effective against biofilm related impacts.

A new device for rapid evaluation of biofilm formation potential by bacteria

This work describes the implementation of a new assay named the BioFilm Ring Test® to evaluate the ability of bacteria to form biofilms. This assay is based on the immobilisation (or not) of magnetic beads embedded by bacterial aggregates or mats (pattented concept). It is realised on modified polystyrene 96-wells microtiter plates with individual 8-wells slides. The kinetic of biofilm formation of four bacterial species, Listeria monocytogenes, Escherichia coli, Staphylococcus carnosus and Staphylococcus xylosus was evaluated with this new device by comparison with the standard crystal violet staining method of sessile cells. In parallel, the biofilm growth was visualized by Scanning Electron Microscopy (SEM) observations. The BioFilm Ring Test® gave similar but faster results than the crystal violet method. Moreover, the new assay was easier to implement, more reproducible and allowed high throughput screenings due to limited manipulations (no washing and staining steps) and rapid and accurate measurements of magnetic bead immobilisation by sessile bacterial cells.

Susceptibility of adherent organisms from Pseudomonas aeruginosa and Staphylococcus aureus strains isolated from burn wounds to antimicrobial agents

To assess the bactericidal effects of ciprofloxacin, netilymicin, and polymyxin B on adherent Pseudomonasaeruginosa organisms and also the bactericidal effects of ciprofloxacin, vancomycin and teicoplanin on adherent Staphylococcusaureus cells, a simple end-point microplate assay, based on the method described by Miyake et al. was used in the present study. As results of the assay, the minimal inhibitory concentration (MICADH) values are taken, which express the susceptibility of the bacterial cells spontaneously released from the surface of adherent microcolonies to antimicrobial agents. Also, a minimal bactericidal concentration (MBCADH) value was read, which is defined as the lowest antibiotic concentration required to kill the sessile bacterial cells. For twenty P. aeruginosa strains and nineteen S. aureus strains isolated from burn wounds, an enhanced resistance against bactericidal action of the applied antibiotics was observed when bacterial cells were attached to polystyrene surface. The MICADH values were comparable with the conventional MIC values only for ciprofloxacin and netilmicin for P. aeruginosa strains. The MBCADH values exceeded many times the conventional MBC values for the majority of strains. The validity of the assay was estimated in the experiment designed to determine the concentration of ciprofloxacin that should be released topically from the collagen dressing to prevent the biomaterial from microbial colonization and allow the decontamination of the wound.

A 140-kilodalton extracellular protein is essential for the accumulation of Staphylococcus epidermidis strains on surfaces.

Two distinct pathogenic mechanisms, adhesion to polymer surfaces and subsequent accumulation of sessile bacterial cells, are considered important pathogenic steps in foreign body infections caused by Staphylococcus epidermidis. By using mitomycin mutagenesis, we have recently generated a mutant, strain M7, from S. epidermidis RP62A which is unaffected in adhesion but deficient in accumulation on glass or polystyrene surfaces and lacks a 115-kDa extracellular protein (designated the 140-kDa antigen; F. Schumacher-Perdreau, C. Heilmann, G. Peters, F. Götz, and G. Pulverer, FEMS Microbiol. Lett. 117:71-78, 1994). To evaluate the role of this protein in accumulation, we harvested extracellular proteins from S. epidermidis RP62A grown on dialysis membranes placed over chemically defined medium, purified the protein by using ion-exchange chromatography, determined its N-terminal amino acid sequence, and raised antiserum in rabbits. The antibody recognized only a single band in a Western immunoblot of the crude extracellular extract. With the microtiter biofilm test, antiserum at a dilution of < or =1:1,000 blocked accumulation of RP62A up to 98% whereas preimmune serum did not. The 140-kDa antigen was found only in extracellular products from bacteria grown under sessile conditions. Of 58 coagulase-negative clinical isolates, 32 strains were 140-kDa antigen positive and produced significantly larger amounts of biofilm than the 26 strains that were 140-kDa antigen negative. The 140-kDa protein appears to be biochemically and functionally unrelated to any previously described factors associated with biofilm formation. Thus, the 140-kDa antigen, referred to as accumulation-associated protein, may be a factor essential in S. epidermidis accumulation and, due to its immunogenicity, may allow the development of novel immunotherapeutic strategies for prevention of foreign body infection.