Browsing by Author "Zheng, Zhilan"

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Growth limitation of Staphylococcus epidermidis in biofilms contributes to rifampin tolerance
(2004-01) Zheng, Zhilan
Tolerance of Staphylococcus epidermidis in biofilms to killing by rifampin was correlated with limitation of bacterial growth in the biofilm state. Intact biofilm experienced a 0.62 log reduction when treated with 0.1 [mu]g rifampin/ml for 4 h whereas the same treatment of exponential-phase planktonic cells produced a log reduction of 4.48. Stationary-phase planktonic cells were nearly as tolerant as intact biofilm cells, experiencing a 1.11 log reduction. Biofilm bacteria grew at only 10% of the maximum rate at which they grew on the same medium in planktonic culture. Killing was localized near the surface of the biofilm adjacent to the nutrient source, as revealed by staining with a respiratory dye. Increased nutrient concentration during antibiotic treatment enhanced killing of biofilm cells. Changing the oxygen tension in the gas phase above the biofilm during antibiotic treatment barely affected killing. It was hypothesized that the biofilm harbors significant numbers of stationary-phase-like cells in the nutrient-limited depths of the biofilm, and that these inactive cells are the ones that survive antibiotic challenge.
Investigation of Staphylococcus epidermidis biofilm resistance to rifampin
(Montana State University - Bozeman, College of Engineering, 2001) Zheng, Zhilan
Observations of cell cluster hollowing in Staphylococcus epidermidis biofilms
(2007-04) Stewart, Philip S.; Rani, Suriani A.; Gjersing, Erica L.; Codd, Sarah L.; Zheng, Zhilan; Pitts, Betsey
Microbial biofilm formation appears to involve complex multicellular behaviours. For example, some bacteria exhibit extensive twitching and swarming motility after association with a surface. These forms of motility appear to be coordinated and to contribute to the spatial organization of biofilm structures (O’Toole and Kolter 1998; Klausen et al. 2003). Another intriguing phenomenon is the appearance of hollow interiors in biofilm cell clusters. Such hollowing seems to occur in the later stages of biofilm development. Hollow biofilm structures have been described for Pseudomonas aeruginosa (Sauer et al. 2002; Webb et al. 2003; Hunt et al. 2004; Parsek and Fuqua 2004; Stapper et al. 2004), Pseudomonas putida (Tolker-Nielsen et al. 2000), Pseudoalteromonas tunicate (Mai-Prochnow et al. 2004) and Actinobacillus actinomycetemcomitans (Kaplan et al. 2003) biofilms. Particularly, striking are movies in which motile cells can be seen seething in the centre of a cell cluster containing many immotile cells (Tolker-Nielsen et al. 2000; Hunt et al. 2004). Here, we report the direct microscopic observation, by a suite of techniques, of hollow cell clusters in Staphylococcus epidermidis biofilms.
Penetration of rifampin through staphylococcus epidermidis biofilms
(2002-03) Zheng, Zhilan; Stewart, Philip S.
Rifampin penetrated biofilms formed by Staphylococcus epidermidis but failed to effectively kill the bacteria. Penetration was demonstrated by a simple diffusion cell bioassay and by transmission electron microscopic observation of antibiotic-affected cells at the distal edge of the biofilm.